PRACTICAL MANUAL ON WEED CONTROL

DEPARTMENT OF AGRONOMY College of Agriculture Orissa University of Agriculture and Technology

PRACTICAL MANUAL ON WEED CONTROL

Revised by Dr. G. C. Mishra Dr. T. Barik Dr. R. K. Paikray Dr. J. M. L. Gulati Dr. S.N. Jena

DEPARTMENT OF AGRONOMY College of Agriculture Orissa University of Agriculture and Technology 2010 (Ebook prepared by: Dr. T. Barik, Professor on 26. Feb. 2013) ([email protected])

CONTENTS Sl No.

Topic

Page

Exercise 1

Classification of weeds

1

Exercise 2

Collection and preservation of weeds

5

Exercise 3

Propagation and dissemination of weeds

7

Exercise 4

Identification of weeds

9

Exercise 5

Biology of purple nutsedge

16

Exercise 6

Biology of Bermuda grass

18

Exercise 7

Biology of carrot grass

19

Exercise 8

Biology of Celosia argentia

22

Exercise 9

Classification of herbicides

24

Exercise 10

Weed sampling and vegetation analysis

26

Exercise 11

Herbicide formulation

28

Exercise 12

Identification of herbicide

29

Exercise 13

Herbicide spraying devices

33

Exercise 14

Different types of sprayers

34

Exercise 15

Study on different types of nozzles

37

Exercise 16

Study of herbicide calculations

38

Exercise 17

Calibration of sprayers

40

Exercise 18

Principles and Methods of herbicide application

42

Precautions for proper application of herbicides

44

Exercise 20

Evaluation of herbicide application

45

Exercise 21

Maintenance of sprayers

46

Exercise 22

Study on allelopathy

47

Exercise 23

Study on weed seed dormancy

48

Exercise 24

Study on weed seed germination at different soil depths

49

Exercise 25

Study on crop weed competition

50

Exercise 26

Phytotoxicity symptoms in different crops

52

Exercise 27

Weed survey

55

Exercise 19

EXERCISE - 1* Classification of weeds Instructional objectives The student should be able to - acquire knowledge about the weeds of various classes - follow appropriate management practices to manage weeds - know about the method of multiplication of various classes of weeds Relevant information Why is classification of weeds required? There are over 30,000 species of weeds around the world of which about 18,000 cause serious losses. Each weed species does not require specific control measures and nature and mode of infestation of weeds also differ. Several weed species need complete eradication, some species may require prevention and others may require control or suppression momentarily for obtaining maximum return from the habitat. But several weed species respond alike to a common weed management practice because they are similar in their habitat, life-cycle, growth habit, morphology, method of propagation, growing season and growth duration. Therefore, it is essential to acquire appropriate knowledge about the weeds of various classes so that one can follow appropriate management practices to manage then successfully. What are weeds? Weeds are plants growing where they are not desired. In other words, weeds are the plants which are out of place, unwanted, non-useful, often, prolific and persistently competitive, harmful, even poisonous, interfere with agricultural operations, increase labour requirement, and add to the cultivation costs, reduce yields and take away the comforts of life. Classification Based on certain criteria, weeds are classified in the following ways. Sl. No 1.

Criteria

Weed group types

Origin

I. Alien (foreign in origin) Argemone mexicana (Anthrophytes) II. Indigenous country, India

1

Example of weeds

to

a

2.

Life cycle

I. Annuals a. Kharif seasonal

Ludwigia parviflora

b. Rabi seasonal

Chenopodium album

c. Summer seasonal

Physalis minima

d. Multi seasonal

Echinochloa colona

II. Biennials

Daucus carota

III. Perennials a. Simple perennials

Lantana camara

b. Bulbous perennials

Allium vineale

c. Creeping perennials

3.

Shallow rooted

Cynodon dactylon

Deep rooted

Sorghum halepense

Stem character I. Aerial stem a. Herbs

Eclipta alba

b. Shrubs

Abutilon indicum

c. Bushes

Zizyphus nummularia

d. Trees

Ficus bengalensis

II. Subaerial stem a. Nuts

Cyperus rotundus

b. Rhizomes

Inula indica

c. Runner

Oxalis corniculata

d. Stolon

Colocasia antiquorum

2

e. Offset 4.

Pistia stratiotes

Form of stem I. Strong a. Herbacious

Sphenoclea zeylonica

b. Woody

Lantana camara

II. Weak a. Trailing

5.

6.

Prostrate

Oxalis corniculata

Procumbent

Tridax procumbens

Diffuse

Boerhavia diffusa

b. Creeping

Sorghum halepense

c. Climbing

Convolvulus arvensis

Plant morphology I.

Dicot leaved

or

broad Cleome viscose

II.

Monocot or narrow leaved a. Grasses Cynodon dactylon b. Sedges

Cyperious rotundus

I.

Terrestrial

Chenopodium album

II.

Aquatic

Habitat

a. Floating Free floating

Eichhornia crassipes

Rooted floating

Ludwigia adscendens

b. Submerged 3

Hydrilla verticillata

7.

8.

9.

c. Emerged

Saggitaria sagittifolia

d. Algal

Chara zeylanica

e. Ditch bank

Marsilea quadrifolia

III.

Amphibious

Ranunculus aquatilis

I

Basophiles

Sporobolus diander

II.

Acidophiles

Petridium aquilinum

III.

Neutrophiles

Celosia argentia

I.

Total parasitic Cuscuta reflexa (stem parasitic)

II.

Semi parasitic (root Orobanche cernua parasitic)

I.

Season bound

Ludwigia kharif)

II.

Crop bound

Orobanche cernua (in tobacco)

III.

Crop associated

Phalaris minor (in wheat)

Soil reaction

Dependence on other hosts

Association parviflora

(in

Source: Practical Manual on Crop Production (1997), Department of Agronomy, CA, OUAT, Bhubaneswar

4

EXERCISE - 2 Collection and preservation of weeds Instructional objectives The student should be able to know the - method of collection of weeds - steps involved in processing of weeds - preparation of herbarium and preservation of weeds. Relevant information Collection of weed The detail information on weeds is necessary for planning effective weed management. The knowledge about the weeds can be obtained through well-planned collection. The collected specimens are kept in the herbarium to keep the record of the weed flora. A specimen- The specimen represents a total plant free from damages due to pest and mechanical injury. Roots are most important and never be excluded except in shrubs, trees and vines. If the specimen is too large, as in case of woody plants or climbers, the plant may be fragmented in to 2,3 or more parts. Where difference is observed between new and old leaves both should be included. It is ideal to collect the specimen with flower and fruits. Grasses and sedges should be collected with well developed inflorescence to facilitate proper identification. A long stem may be broken and bent into a V, N or W shape. Excess branches or leaves are removed provided enough base is left for clear visualization of the specimen. The sections of stem are not discarded, as variations in internodes are important identifying features. Large leaves are cut in halfs or smaller pieces and kept in adjacent sheets in the herbarium. The succulent and thick plants take more time for drying. Those specimens are subjected to artificial heating in order to prevent rotting and fungal infection. So the tissues of such specimen should be killed by dipping in boiling water or by treating with alcohol or strong formaline. Materials required i. Vasculum or polythene bag

vi. Khurpi

ii. Slanted slips of thick paper

vi. Field press

iii. Knife

viii. Blotting paper/ Absorbent drying paper

iv. Secateur/small clippor/cutter

ix. Slanted slips of thick paper

v. Pick axe

x. cello tape

Vasculum- It is a metallic box of size 50 cm x 30 cm x15 cm made up of tin or aluminum and provided with tight lid. It should be very light in weight for easy carrying. The box is painted white to reflect light. It is used for carrying the samples after collection. During hot 5

weather water is sprinkled inside the box to avoid desiccation of specimen in it. If vasculum is not available, polythene bag, wooden basket or cardboard cartoons can be used for the purpose. Polythene bags – This should be of thick quality and good size to accommodate large samples. Knife-Gardener’s knife or any knife may be used Secateur/small clipper- It is used for cutting of small twigs of shrubs. Pick axe - It is used for uprooting the herbs and bulbous plants. It should be light with pick point and chisel end. Field press- It is made up of simple hard board or thin ply wood of 30 cm x 42 cm size and tied by two leather or cotton straps. Between these a number of drier or blotting paper containing plant specimens are placed. Field press should be as light as possible. Procedure Preservation of weed (making a herbarium) Preservation of specimen includes drying, identification, mounting and labeling of specimens in the herbarium. a. Preservation of sample i) Poisoning of specimen-The specimen after collection is poisoned to kill the plant so that formation of abscission layer is prevented. Several dipping it in 15 to 20% mercuric chloride solution do the poisoning of samples. ii) Use of 10% formaline solution iii) Fumigation with methyl bromide, carbon disulphide or carbon tetrachloride. Fumigation should be done at regular intervals at the place of preservation of the specimen. iv) At some places electric heaters are used for killing the specimen and disinfections. b. Mounting The specimen is fixed on the mounting sheet after it is dried and poisoned. The mounting sheets are made from heavy, long lasting white card sheets in uniform size of 42 cm x 28 cm. Only one specimen is placed in single sheet. The root portion of the specimen should be at bottom of the sheet. Some portion at right hand corner is left for label. The specimen is neatly and uniformly spread on the white sheet and then fixed. c. Fixing and stitching the specimen on the sheet The common technique of fixing the specimen on sheet is done using glue. The glue is uniformly spread over the glass plate of 50 cm x 35 cm size. The specimen is placed 6

on the glass and then immediately mounted on the mounting sheet. On the other method, the weed specimen is placed on a smooth surface and glue is applied on all parts of the plant by brush followed by mounting. d. Strapping In this process, the specimen is not glued on the sheet but strapped by thread stitches. Paper tapes or adhesive tapes are used for strapping. For stitching continuous loops of thread should be avoided. Each stitch should be independent of others by knot given on the back of mounting sheet. e. Labeling After mounting of specimen, the herbarium sheet is labeled. The information recorded in the note book with the same reference number written on the news paper when the specimen was collected should contain the following use trial information. i) Exact map locality- The locality from where the specimen was collected is mentioned as kilometers by high way from the center of a fairly large town in the same district provided that the distance is less than 30 kms. ii) Date of collection- The date of collection along with month and years should be mentioned. iii) Habitat- Specific place (field, road side, aquatic bodies, hill side), soil (sand, silt, clay, gravel), exposure (sun or shade) moisture condition (wet, moist, dry) and denseness of community (bare ground, dense thickets) are ascertained from the place of collection. EXERCISE - 3 Study on propagation and dissemination of weeds Instructional objective The students should able to -

study the mode of reproduction and dispersal of weeds in order to plan their effective prevention and control measure. Relevant information Weed propagation Weeds are reproduced both by sexual and asexual method. a) Sexual method of propagation- Sexual method refers to conjugation and fertilization of gametes resulting in seed production. Majority of weeds are propagated by distinct seed production. Seed production is prolific in annual and biennial weeds. Such weeds produce few thousand of seeds per plant in their life cycle. The seed production in perennial weeds is limited in few weeds like bermuda grass and nut sedge. But other perennial weeds like 7

tiger grass and Canadian thistle do have prolific seed production potentiality. Those seeds are the source of reinfestation after maturity. The seed production capacity of certain common weeds is noted by counting the number of seeds/plant through magnifying glass. The observations are recorded on the seed production on plant in different weed species. It is recorded by the assigned group. b) Asexual reproduction. The vegetative propagation of weeds takes place either from their vegetative part like stem, leaf or from roots. The weeds may produce some specific modified vegetative organs both above and under the ground. Those modifications are in the form of rhizomes, tubers, stolons, suckers, offsets, bulbs, bulbils and rootstocks. The perennial weeds are mostly reproduced by vegetative propagules. i) Rhizome- It is an underground modified shoot having nodes, internodes buds and scaly leaves. Rhizomes grow fast in all the directions with in soil and produce new aerial shoot invading large area in short period. Broken fragments of rhizomes give rise to new plants and new weed colonies. Perennial grasses, sedges and certain broad leaved weeds including some ferns reproduce vegetatively through rhizomes. Rootstock is a form of rhizome but it penetrates downwards in the soil such as Johnson grass. ii) Runner - Creeping type of weeds like bermuda grass, wood sorrel and pennywort produce special aerial shoot called runners from the axils of their lowest leaves. The runners spread in the soil in different directions and produce roots from their terminal buds at short distances. Then the new shoots are developed from the crown region. Daughter plants of such weeds also reproduce and occupy large areas. iii) Stolon, suckers and offsets- when a runner rises in the form of an arc before hitting the soil surface is called a stolon. The weeds of rosaceae propagate by stolons. Suckers trail below the soil surface as in hawk weed. Runners of floating weed like water hyacinth and water lettuce are called offsets. iv) Tubers- Swollen end of rhizomes and suckers are called tubers. A tuber possesses scaly leaves, in conspicuous nodes and internodes and tiny buds which give rise to new shoots and roots as in case of nut sedge. v) Bulb- In bulbs the crown region of plant is compressed in the shape of a disc. It contains many fleshy leaves, auxiliary bud and a flowering bud at its apex. Wild onion and garlic propagate by bulbs. vi) Bulbils- It is the modification of vegetative or flower buds. It is commonly observed in wood sorrel. In hydrilla, the bulbils originate from leaf axils called as turions. vii) Stem and roots - Fragments of stem and roots of some weeds give rise to new individuals. Detached stem pieces of dodder, prickly pear, roots of field bind weed and Canadian thistle are common means of propagation. 8

B) Dispersal of weeds - Dispersal of mature seeds and live vegetative parts of weeds is nature’s way of providing non competitive sites to new individuals. Wind water and man are the agents for dissemination of weeds. Morphology of weed seeds pays a key role in spreading of weeds from one region to other. a) Wind dispersal –The weed seeds are very tiny and light or have special organs to keep them afloat. The grassy and parasitic weeds like dodder plant and witch weed seeds are easily blown away by wind. In Mexican poppy, wind swings the plant and seeds from the nature. The capsules are dispersed to a greater distance. It is called as censer mechanism. Some structures in the seed help a lot in such dissemination. Those organs are as follows i) Pappus- It is the parachute like modification of persistent calyx in to hairs found in weeds of family asteraceae. ii) Comose- Weed seeds are carried with hairs partially or fully as observed in swallowwort. iii) Balloon-It is a modified papery calyx that encircles the fruit loosely along with entrapped air as found in ground cherry. b) Water dispersal –Weed seeds move with surface run off water, natural streams and irrigation and drainage channels down the stream. Aquatic weeds drift either as whole plant, plant fragments or as seeds through water currents. c) Dispersal by animals and birds-The weeds like cocklebur, puncture vine and prickly chaff flower have special structures like hooks, sharp spines and scarious bracts, respectively, which stick to the skin, hair or hooves of animals and disperse with their movement. Several birds pick up fruits and seeds of weeds by their wing, feet or beak and drop these away during flight. The parasitic weed bird vine seed sticks to the beak of birds and are transferred to new branches of trees when birds rub their beak against them. d) Dispersal by man – Careless act of human beings are greatly responsible for dispersal of weeds. Farm machineries carried from one field to other with out clearing carry numerous weed seeds with them. Many weeds have been carried by human beings during traveling though out the globe. e) Dispersal through manure and silage- Farmyard manure is an important source of dissemination of weeds since viable weed seeds are present in the dung of the farm animals. Four months of proper composting devitalizes all weed seeds. .EXERCISE - 4 Identification of weeds Instructional objectives The student should be able to - study, identify and acquaint with the common weeds of the locality. 9

- gain an idea regarding biological and ecological adaptations. Relevant information Weed identification Identification is the first step in naming the plant. There are numerous weeds present in an area. Weeds differ in their morphology, habitat, life cycle, growth, growing in association with specific crops, stage of competition with crops, resistance/susceptibility to different insect, pathogens herbicides and various methods of weed management. Weed identification is necessary to estimate the magnitude of their harmful effects on crop production and planning an effective weed management strategy. Materials required i. Note book and pencil ii. Polythene bags with rubber bands iii. Magnifying glass Procedure Visit to a farm and record the weed species occurring in different farming situations such as up land, low land and irrigated field along with weeds present in the waste land and farm pond. Observation The following observations were recorded in tabular manner to make the lists of weeds present in the OUAT Agronomy farm. Sl No

Local name

Common name

Botanical name

Family

Habitat

(Odia) Annual monocot weeds 1

Nali suan

Jungle rice

Echinochloa colona

Poaceae

Upland

2

Bada suan

Barnyard grass

Echinochloa crusgalli

Poaceae

Upland and Medium land

3

Kodua

Kodo

Paspalum scrobiculatum

Poaceae

Upland

4

Kaugodia

Crows

Dactyloctenium

Poaceae

Upland

foot

10

grass

aegyptium

5

Kankada ghasa

Crab grass

Digitaria sanguinalis

Poaceae

Upland

6

Jhari ghasa

Sporobulus

Sporobolus diander

Poaceae

Upland

7

Anamandia

Indian grass

Poaceae

Upland

8

Bilua lanji

Chinese sprangle top

Leptochloa chinensis

Poaceae

Medium and low land

9

Mayurchulia

Rhodes grass

Chloris barbata

Poaceae

Up land

Poaceae

Wheat and

goose Eleusine indica

Winter annual monocot weeds 1

Gahunsa (Hindi)

Little grass

canary Phalaris minor

Barley 2

Bana jaba

Wild oat

Avena sativa or Poaceae fatua ?

Wheat and Barley

Perennial monocot weeds 1

Duba ghasa

Bermuda grass Cynodon dactylon Poaceae

Up, medium and low land

2

Regeda

Torpedeo grass

Panicum repens

Poaceae

Upland

3

Panikodo

Knot grass

Paspalum conjugatum

Poaceae

Medium land

4

Juna

Thatch grass

Imperata cylindrica

Poaceae

Upland

5

Khadi ghasa

Tiger grass

Saccharum imperata

Poaceae

Upland

6

Bena

Vetivera

Vetivera zizanioides

Poaceae

Upland

11

7

Baru and Jhonson grass Kalamucha (Hindi)

8

Sorghum halepense

Poaceae

Upland

Leersia

Leersia hexandra

Poaceae

Lowland

Annual sedges 1

Chhata juania

Rice flat sedge

Cyperus iria

Cyperaceae

Medium and low land

2

Mutha jatiya

Common sedge

Cyperus diffornis

Cyperaceae

Medium and low land

3

Mutha jatiya

Yellow sedge

Cyperus esculentus

Cyperaceae

Cyperus

4

Pania patri

Lesser fimbristylis

Fimbristylis miliacea

Cyperaceae

Cyperus

Kyllinga

Kyllinga sps

Cyperaceae

Upland

Cyperus rotundus

Cyperaceae

Cultivated field

5

nut

Perennial sedges 1

Mutha

Purple sedge

nut

2

Santra

Cyperus

Cyperus grossus

Cyperus

Swampy places

3

Sanagai chira

Scirpus

Scirpiss acutus

Cyperaceae

Lowland paddy

4

Badagai chira

Scirpus

Scirpus maritimSus

Cyperaceae

Lowland paddy

Annual broad leaved weeds 1

Bada pokasungha

Bill goat weed

Ageratum conyzoids

Asteraceae

Upland crops

2

Kanta tulasi

Bristly starburc

Acanthospermum hispidum

Asteraceae

Upland crops

3

Kanta leutia

Slender amaranthus

Amaranthus viridis

Amaranthaceae

Upland crops

4

Kanta leutia

Aamaranths

Amaranthus spinosus

Amaranthaceae

Upland crops

12

5

Agni buti (Hindi)

Monarch red stem

Ammania baccifera

Lythraceae

Waste land

6

Agara

Mexican poppy

Argemone mexicana

Papaveraceae

Lowland rice

7

Sola

Cork plant

Aeschynomene indica

Fabaceae

Lowland rice

8

Pathara chata

Spider ling

Boerhavia diffusa

Ntctaginaceae

Upland crops

9

Balichanari

Borreria

Borreria hispida

Rubiaceae

Upland crops

10

Bana chakunda

Coffee senna

Cassia occidentalis

Fabaceae

Upland crops

11

Bana chakunda

Wild indigo

Cassia tora

Fabaceae

Upland crops

12

kanasiri

Days flower

Commelina benghalensis

Commelinaceae

Upland crops

13

Anasorisha

Spider flower

Cleome viscosa

Capparadaceae

Upland crops

14

Lahanga

Cocks comb

Celosia argentea

Amaranthaceae

Upland crops

15

Lanka marichia

Croton

Croton sparsiflorus

Euphorbiaceae

Upland crops

16

Keshadura

Asthama weed

Eclipta alba

Asteraceae

Lowland crops

17

Chitakutia

Garden spurge

Euphorbia hirta

Euphorbiaceae

Upland crops

18

Hatisundhia

Heliotropium

Heliotropium indicum

Borraginaceae

Upland crops

19

Gayasha

Leucas

Leucas aspera

Lamiaceae

Upland crops

20

Labangi

Winterprimose Ludwigia parviflora

Onnagraceae

Lowland rice

`21

Bilinalita

Red weed

Melochia corchorifolia

Sterculiaceae

Upland crops

22

Lajakuli

Sensitive plant

Mimosa pudica

Fabaceae

Upland crops

23

Hansapadia

Monochoria

Monochoria vaginalis

Pontederiaceae

Lowland rice

13

24

Gharpodia

Oldenlandia

Oldenlandia corymbosa

Rubiaceae

Upland crops

25

Badianla

Niruri plant

Phyllanthus niruri

Euphorbiaceae

Upland crops

26

Balubaluka

Common purselane

Portulaca oleracea

Portulacaceae

Upland crops

27

Photaka phal

Ground cherry

Physalis minima

Solanaceae

Upland crops

28

Pashanabhedi

Scoparia

Scoparia dulcis

Scrophulariaceae

Upland crops

(Sanskrit) 29

Nunukoli

Night shade

Solanum nigrum

Solanaceae

Upland crops

30

Kauthantia

Goose weed

Sphenoclea zeylanica

Sphenocleaceae

Lowland rice

31

Puruni

Horse purselane

Trianthema portulacstrum

Aizoaceae

Upland crops

32

Gokhara

Puncture vine

Tribulus terrestis

Zygophyllaceae

Upland crops

33

Bisalyakarani

Tridax

Tridax procumbens

Asteraceae

Upland crops

Winter Annual Broad leaved weeds 1

Krushna nil

Pimpernel

Anagallis arvensis

Primulaceae

Upland crops

2

Bathua

Lambs quarters

Chenopodium album

Chenopodiaceae

Upland crops

3

Phulphulia

Curd weed

Gnaphallium indicum

Asteraceae

Upland crops

4

Anichana

Lathyrus

Lathyrus sativa

Fabaceae

Upland crops

Convolvulaceae

Upland crops

Fabaceae

Upland crops

Summer Perennial broad leaved weeds 1

Hiranya khuri

Field weed

bind Convolvulus arvensis

2

Kuradhia

Beggar weed

Desmodium triflorum

14

3

Sunusunia

Marsilia

Marsilia minuta

Marsiliaceae

Lowland rice

4

Ambiliti

Wood sorrel

Oxalis corniculata

Oxalidaceae

Upland crops

Parasitic Weeds 1

Nirmuli

Dodder plant

Cuscuta chinensis

Convolvulaceae

Upland crop of niger, berseem and forest and plantation rops

2

Lalagia (Hindi)

Witch weed

Striga asiatica

Scrophulariaceae

Upland crop of maize, jowar & bajra

3

Thokra (Hindi)

4

Broomrape

Orobanche cernua

Orobanchaceae

Upland crop of brinjal, tomato, tobacco and rapeseed/ mustard

Bird vine

Loranthus longifolius

Loranthaceae

Orchard and forest trees

Aquatic weeds 11

Bilati dal

Water hyacinth

Eichhonia crassipes

Pontederiaceae

Floating aquatic weed

2

Kataki dal

Water lettuce

Pistia stratiotes

Araceae

Floating aquatic weed

3

Chingudiadal

Hydrilla

Hydrilla verticillata

Hydrocharitaceae Submerged aquatic weed

4

Panikadalia

Ottelia

Ottelia alismoides Hydrocharitaceae Submerged aquatic weed

5

Kain

Lily

Nymphea stellata

Nymphaceae

Attached floating

6

Padma

Lotus

Nelumbium nucifera

Nymphaceae

Attached floating

Typha

Typha angustata

Typhaceae

Emerged

7

15

aquatic weed 8

Kunchidal

Water fern

Salvinia molesta

Salviniaceae

Free floating

9

Gandhi

Chara

Chara zeylanica

Characeae

Water logged area in rice

Nitella

Nitella hyaline

Characeae

Water logged area in rice

Amaranthaceae

Grass land

Aegemone mexicana

Papavoraceae

Waste land

Problem weeds 1

Apamaranga

Prickly flower

chaff Achyranthus aspera

2

Agara

Mexicana poppy

3

Bana pokasungha

Eupatorium odoratum

Asteraceae

Forest

4

Naga aeri

Laantana camara

verbenaceae

Forest

3

Mikania

Mile a minute

Mikania micrantha

Asteraceae

Fruit and forest trees

4

Gajar ghasa

Carrot weed

Parthenium hysterophorus

Asteraceae

Waste land

5

Bada gokhara

Cockle bur

Xanthium strumarium

Asteraceae

Grass land

EXERCISE – 5 Biology of purple nut sedge (Cyperus rotundus) Knowledge of weed biology is essential for the development of economic and environmentally acceptable weed management systems. To establish weed control strategies it is important to recognize the natural strategies of major weeds infesting a crop. Weed biology relates to plant attributes such as morphology, seed dormancy and germination, growth physiology, competitive ability and reproductive biology. Understanding weed biology with respect to different environmental, edaphic and management factors offers a key to improved weed management strategies such as different stages of susceptibility for weed control.

16

Instructional objective The student should be able to - study the biology of purple nut sedge. Relevant information The family cyperaceae has around 3000 species out of which more than 200 are weeds including purple nut sedge. This is considered as a worst weed of the world as it causes a great problem in agriculture and horticulture. It has the ability to thrive under very adverse conditions and is very difficult to be eradicated. In fact it can resist both swampy and drought (after establishment) conditions. Once invaded it is next to impossible to be eradicated fully due to prolific production of tubers. Tubers are some times called as nut due to its appearance. Identification of the weed It is a sedge and has a triangular stem around which three number of leaves occur in one whorl. The leaves have parallel venation, shinning green in colour due to some waxy coating, thin in comparison to those of grasses and arise from the bulb. Leaves have a distinct ridge along the mid vein. Leaves do not possess hairs, auricles or ligules. The plant is erect and unbranched. The stem has no branching and ultimately gives rise to an inflorescence. The inflorescences contain 3 - 9 peduncles of different length each having 3 - 40 hermaphrodite flowers. The fruit is an achene and propagation through them is almost negligible. The tubers are oval to spherical in shape and have 3 - 10 buds arranged spirally. Bulbs are variable in size, initially look white and turn brown, dark brown and black gradually. The tubers can be small (0.1 g – 0.258 g), medium (0.26 – 0.58 g) and large (> 0.58 g). These tubers are produced on rhizomes (underground stems) that grow as deep as 20 to 30 cm below the soil surface. Tubers are covered with red or red-brown scales and are formed in chains. Tubers are rough, oblong and have oval to spherical shapes. These tubers are bitter to the taste. The majority (>80%) of tubers can be found in the top 15 cm of soil. Inflorescence is yellowish purple in colour, and is a simple or compound umbel having leaf like bracts at the base of the flower head. Life cycle Purple nut sedge is a perennial plant. It has a complex system of basal bulbs, rhizomes and tubers. The bulbs give rise to new plants. After few days lateral rhizomes are formed which give rise to another bulb under the influence of light. Thus a chain of rhizomes and bulbs are formed. The formation of the lateral rhizomes from the basal bulb starts 4 to 6 weeks after the appearance of the first aboveground shoots. Tuber production in the field can be as large as 100 per plant in temperate areas up to one thousand in tropical areas. The tubers function like the seeds of annuals, and act as dispersal units. The tubers remain dormant for some time at the end of the growing season to which they have 17

been acclimatized. Its leaves and flowering stalks generally die after maturity, but tubers and rhizomes survive in the soil and sprout again, may be, for 10 to 12 times. The tubers can survive for 1 to 3 years. NB: (IRRI Manual) A bulb is an underground bud. Rhizomes are underground shoots with short, thick internodes buried in the soil. They have specialized buds that can remain dormant. These shoots are rich in stored food and enable plants to survive from year to year. Stolons are horizontally growing stems with long slender internodes; adventitious roots form at the nodes when in contact with soil. A tuber is a specialized structure that results from the swelling of the terminal portion of an nderground stem or root; it contains stored food. EXERCISE – 6 Biology of Bermuda grass (Cynodon dactylon) Instructional objective The student should be able to -

study the biology of Cynodon dactylon

Relevant information Bermuda grass (Cynodon dactylon) is also known as Bahama Grass, Devil's Grass, Couch Grass, Wire grass, Indian Doab, Dog's tooth grass, Indian Doab, Grama, and Scutch grass. It is native to South east Africa. It is called Bermuda grass in the United States because it was introduced from the Bermuda Island. Bermuda grass is considered a very invasive and competitive weed. It spreads very rapidly in to cultivated fields. Identification Cynodon dactylon is found in warm climates all over the world between 45° south and 45° north latitude. It is a hardy, fine leaved perennial grass growing in open areas where there are frequent disturbances such as grazing, flooding, and fire. The erect stems can grow 1– 30 cm tall. The stems are slightly flattened, often tinged with purple color. Branches are fragile. Leaves are rolled in the bud, without auricles, and have a ligule that is approximately 1/2 mm long. Ligules are short and membranous with a ciliate apex. Leaf blades are approximately 5 to 10 cm long and 2 to 3 mm wide. Leaves are found on opposite sides of the stem. Leaves may be hairy or hairless .The blades are grey-green in colour and are short, with rough edges. Blades are flat to slightly keeled and pubescent towards the base. The tuft of hairs in the collar (where blade meets the sheath) region helps 18

to distinguish this weed from most other grasses. The sheaths are also slightly keeled, pubescent at the apex and along the apical margin. It has a deep root system; in drought situations the root system can grow to over 2 m deep, though most of the root mass remains within 60 cm depth. The grass creeps along the ground and root wherever a node touches the ground, forming a dense mat. Rhizomes and stolons both occur on the same plant. Rhizomes are scaly while the stolons are flat, smooth and usually bent. The inflorescences are green or purple in color having 3–7 spikes (rarely two) remaining together at the top of the stem in a finger like fashion, each spike 3–6 cm long. Biology C. dactylon reproduces through seeds, through runners and rhizomes. Seeds are spear shaped and brown in colour. Warm moist conditions promote the production of up to 230 seeds per panicle. Seeds germinate at temperatures above 20°C and germination takes place within the next two weeks. The complete cycle from germination to seed production takes around four months. Bermuda grass often grows "under" the canopy of good plants near their stems from where it sends out runners. Thus it grows by sending "runners" both above ground (stolons) and below ground (roots). Its extensive underground root system makes it virtually impossible to eliminate it by either by hand pulling or by spraying of herbicides. It grows vigorously once established. Its stem is fragile which prevents its complete removal by pulling. It has the ability to regrow at a faster rate than any other plant after burning. Key points -

Bermuda grass is adapted to a wide range of soil conditions but is best suited to a well-drained site. Grows in either acid or alkaline conditions and survives floods and drought (through regrowth from underground rhizomes). Its seeds are small, one kg containing around 45 lakh seeds. Its growth is promoted by full sun and retarded by full shade. Bermuda grass can grow in poor soil. During droughts the upper parts die off, but the grass will keep growing from its rhizomes. It is a sacred grass of the Hindus next to tulsi. EXERCISE – 7 Biology of carrot grass (Parthenium hysterophorus)

Instructional objective The student should be able to 19

-

study the biology of Parthenium hysterophorus

Relevant information Parthenium weed is also known as Bitterweed, Carrot grass, Congress grass, gajar ghas, False ragweed, Feverfew, Parthenium, Ragweed, Ragweed parthenium, White top. etc. Native to tropical Americas, Parthenium is an aggressive weed invading all disturbed land, including farms, pastures, and roadsides and fallows, in other words the areas having poor competitive crops. Undisturbed vegetation is least affected.. In some areas, outbreaks have been of almost epidemic proportions, impacting crop production, livestock and human health. It produces a range of toxins which affect other plants and animals. It is not commonly eaten by livestock but can taint meat, and toxins will pass into milk. Regular contact with parthenium causes dermatitis in animals and humans and can cause respiratory problems including asthma. Identification Parthenium weed is an annual herb with a deep tap root and an erect much branched stem that becomes woody with age. As it matures, the plant develops many branches in its top half. Seedlings – cotyledons are a rounded paddle shape, 3 - 4 mm long, borne on short stalks 1 – 2 mm long. The first true leaves are egg-shaped and covered in fine, white hairs. Older leaves become increasingly lobed and deeply divided. Young plants – develop into a rosette, with leaves to 80 - 200 mm long and 40 - 50 mm wide. Its leaves are, alternate, sessile, irregularly dissected, bipinnate, deeply lobed, covered with fine soft hairs and pale green in colour. Leaves resemble those of carrot. Older plants – develop an erect, highly branched stem 30 – 150 cm high, occasionally reaching 2m in deep rich soils and has a deep taproot. Deeply divided leaves develop along the stem, which is deeply grooved. Stems and leaves are covered in short, white hairs. Plants develop a bluish or greyish appearance. Flower heads – Flowering occurs about a month after germination. Flowers occur in clusters at the top of the plant, borne on short stalks, arising from the leaf forks. Flower heads are small, white, 4 - 10 mm across and form an unusual, 5-sided shape, with longer creamy white flolets (ray flowers) in the corners. Flower heads become hard and brown as they mature. Seeds – The fruit is cypsella are striped grey to black and a narrow diamond shape, 2 mm long and flattened. They have a brown tuft on the end formed from 2 broad scales 0.5 mm long. Seeds are tightly grasped in a brown outer coat, which gives them more of a tufted triangle appearance. Each flower contains four to five black seeds that are wedge-shaped, two millimetres long with two thin white scales. Lifecycle/Biology: Parthenium weed, with suitable conditions (rain, available moisture, mild temperatures), can germinate at any time of the year. Plants can flower 4 – 8 weeks after germination, and flowering may continue for 6 to 8 months. Seed has no dormancy. 20

Mature plants have some frost tolerance. It spreads through the plant’s seeds, which are carried by wind, water, animals and humans. It is difficult to control its spread as the plant germinates exceedingly fast and a single plant can produce up to 25,000 seeds, occasionally 1 lakh per plant. It produces flowers and seed throughout its life, after maturity plants die. In summer, plants can flower and set seed within four weeks of germination, particularly if stressed. Parthenium seeds can spread via water, vehicles, machinery, stock, feral and native animals and in feed and seed. Drought conditions aid the spread of seed with increased movements of stock fodder and transports. Germination temperatures for Parthenium occur across the 8 to 30° C range with the optimum germination temperature being 22 to 25° C. Persistence tests demonstrates that more than 70% of parthenium seeds buried at 5cm below the soil surface survive for at least 2 years whereas surface-lying seeds survive for no longer than 6 months. Parthenium weed can germinate, grow, mature and set seed in four weeks. Flood carries its seeds which grows vigorously after the flood water recedes. Key points Nearly 5 million hectares are under threat from the deadly weed parthenium in our country. Parthenium entered India with imported food grains in the mid-1950s. It is thought to have been introduced into Ethiopia and India with contaminated cereal grain, and into Australia in contaminated pasture seed from the USA. The weed has invaded millions of hectares across the country including crop land, wasteland and forest areas, according to DWSR, which is preparing a report on this. Initially, the deadly weed occupied largely non-crop areas such as wasteland, open forests and roadsides. It has now spread to cropping land at an alarming rate Parthenium weed is capable of growing in most soil types but becomes most dominant in alkaline, clay loam soils. Infestations of parthenium weed can degrade natural ecosystems. It releases chemicals that inhibit the germination and growth of pasture grasses and other plants. Hand pulling of small areas is not recommended. There is a health hazard from allergic reactions and a danger that mature seeds will drop off and increase the area of infestation. Growing of competitive legumes such as butterfly pea (Clitoria ternatea) or grasses such as Bisset bluegrass (Bothrichloa insculpta), Buffel grass (Cenchrus ciliaris) can be grown in the heavily infested area to reduce the invasion of the harmful Parthenium. Plants like Cassia sericea, Croton bonplandianus and C. sparsiflorus, Amaranthus spinosus, Sida acuta, Tephrosia purpurea, Stylosanthes scabra, Cassia auriculata and Cassia tora, can compete with the weed and reduce its population.

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In certain parts of our country, crop rotation using marigold (Tagetes spp.) during rainy season, instead of the usual crop, is found effective in reducing parthenium infestation in cultivated areas. EXERCISE – 8 Biology of celosia (Celosia argentia) Instructional objective The student should be able to -

study the biology of Celosia argentia

Relevant information Celosia is also known as cock's comb, cockscomb, feather cockscomb, foxtail amaranth, red spinach, silver cockscomb, quail grass or white cock's comb. Cultivated in many countries. But also occurs as a weed in dry open places such as roadsides and waste lands, as well as stream beds, from sea level to 1200 -1800 m altitude. Probably originally from tropical Africa, but spreading early throughout tropical Asia and Malesia; many cultivars are widely grown in tropical and subtropical areas. It is one of the leading leaf vegetables in south-western Nigeria, where it is known as ‘soko yòkòtò’ in the Yoruba language, meaning ‘make husbands fat and happy’. It is found as a weed in many upland crops s such as Groundnut (Arachis hypogaea , Finger Millet (Eleusine coracana) and Maize (Zea mays). Identification Erect vigorous annual herb, may grow up to 1.5m, simple or with many ascending branches. Stem and branches strongly ridged and often sulcate, quite glabrous; branches up to 25 per plant. Leaves alternate, simple, lanceolate-oblong to narrowly linear, acute to obtuse, without stipules, shortly mucronate with the excurrent midrib, glabrous; lamina of the leaves tapering below into a slender petiole; upper and branch leaves smaller, markedly reducing; leaf axils often with small-leaved sterile shoots. Inflorescence a dense, manyflowered spike, 2.5-20 x 1.5-2.2 cm, silvery to pink, conical at first but becoming cylindrical in full flower, terminal on the stem and branches, on a long, sulcate peduncle up to 0. 20 cm long, which often lengthens during flowering. Inflorescence is pinkish white and the plants can be recognized from a distance in the field. Flowers small, bisexual, regular, 5-merous. Bracts and bracteoles lanceolate or the lower deltoid, 3-5 mm, hyaline, more or less aristate with the excurrent midrib, persistent after the fall of the flower. Perianth segments 6-10 mm, narrowly elliptic-oblong, acute to rather blunt, shortly mucronate with the excurrent midrib, with 2-4 lateral nerves ascending more than halfway up each segment, margins widely hyaline. Filaments very delicate, free part subequalling or exceeding the staminal sheath, sinuses rounded with no or very minute intermediate teeth; anthers and filaments creamy to magenta. Stigmas 2-3, very short, the filiform style 5-7 mm long; ovary 4-8-ovulate, ovary superior. Capsule 3-4 mm, ovoid to almost 22

globular. Seeds 1.25-1.5 mm, lenticular, black, shining, testa very finely reticulate. The flowerheads can last up to 8 weeks, and further growth can be promoted by removing dead flowers. Biology Propagation occurs by seed. Seeds mature in 10–20 weeks from sowing and shatter when the inflorescence is dry. They remain dormant on the soil surface until the start of the next rainy season. Flowering is delayed by repeated cutting of the tender vegetative parts. Pollination is by wind and insects, especially bees and flies, which visit the flowers regularly. Seed maturity starts from the basal part of the inflorescence and gradually moves up to the tip. Consequently, seeds from the basal parts of the inflorescence are more vigorous than those from the middle and apical regions. The 1000-seed weight is 1.0–1.1 g. It emerges several times during a cropping cycle and escapes weed control measures. It produces 2,000 to 3,000 seed per plant which add to the soil seed bank. Celosia comprises about 50 species and occurs in all tropical and subtropical regions. A well-drained sandy loam soil allows optimum growth. Celosia tolerates moderately saline soils of 25–50 mM NaCl. It is moderately resistant to drought and performs well under low water supply of the dry season, but severe drought promotes early flowering. Key points NB: Results of screen house experiment showed that inter-planting C. argentia into sorghum at a ratio of 2:1 suppressed striga best by as much as 48% and resulted in the highest yield increase (100%) compared to the sole sorghum treatment. The laboratory study showed that C. argentia could induce suicidal germination in striga seed by as much as 68% compared to cotton which was taken to be the standard. Olupot, J.R., Osiru, D.S.O., Oryokot, and J., Gebrekidan,B. 2003. The effectiveness of Celosia argentia (Striga ‘‘chaser’’) to control Striga on Sorghumin Uganda. Crop Protection 22: 463–468. www.elsevier.com . The leaves and flowers are edible and are grown for such use in Africa and Southeast Asia. It is a traditional food plant in Africa. Ttolerates poor, dry soil; Celosia is primarily used as a leafy vegetable. The leaves and tender stems are cooked into soups, sauces or stews with various ingredients including other vegetables such as onions, hot pepper and tomato, and with meat or fish and palm oil. Celosia leaves are tender and break down easily when cooked only briefly. The soup is consumed with the staple food of maize, rice, cassava or yam. The young inflorescences are also eaten as a potherb.

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EXERCISE - 9 Classification of herbicides Instructional objectives The student should be able to - acquire knowledge about different classes of herbicides - follow proper use of herbicides for efficient management Relevant information Herbicides are the chemicals used to control / suppress the same targeted plants (weeds) without significantly affecting the economical plants (crops). Herbicides are classified basing upon the chemical structure, method of use, soil or foliage application, selectivity and mode of action. There are about 500 chemicals discovered to manage weeds in different situations. Therefore, it is required to gather knowledge about the herbicides which can be safely used to manage weeds in various crops. Classification: A) Based on chemistry – Herbicides are grouped into inorganic and organic. In organic- It does not contain carbon structure.

i) Acids-Arsenic acid, sulphuric acid ii) Salts –Sodium arsenate, sodium chlorate, Borax, copper sulphate, sodium chloride, ammonium sulphamate, iron sulphate, copper nitrate, sodium chloride, Ammonium thiocyanate. Organic - It contains carbon atom in their molecule and usually act by altering the normal growth pattern of the plant. i) Oils - Diesel oil, stoddard ii) Non oils a) Aliphatics - Dalapon , trichloro acetic acid b) Anilides (Butachhlor, alachhor, metolachlor, pretilachlor, propanil and amides (Napropamide, mefluidide and pronamide) c) Benzoics - Dicamba, Tricamba, chloramben, 2,3,6- Trichloro benzoic acid d) Bipyridiliums – Paraquat, diquat e) Carbamates - Propham, chlropropham, asulam, desmedipham, phenmedipham f) Cyclohexanediones – Clethodim, cycloxidim, sethoxydim,tralkoxydim g) Dithocarbamates - Metham h) Dinitroanilines – Fluchloralin, pendimethalin, trifluralin, nitralin, oryzalin 24

i) Nitriles - Bromoxynil, ioxynil, dichlobencil j) Oxadiazoles- Oxadiazon k) Phenols- Dinoseb, PCP l) Phenoxy carboxylic herbicides i) Phenoxy acetic acid – 2,4, Dichloro acetic acid and 2,4,5 Trichloro acetic acid. ii) Phenoxy butyric acid - 2,4, Dichloro phenoxy butyric acids, 2 Methyl 4 chloro phenoxy butyric acid and 2,4,5, trichloro phenoxy butyric acid. iii) Phenoxy propionic acid- Dichlroprop, dichlofop, fenoxaprop, mecoprop, fluazifop and quizalofop. m) Quinchlorac carboxylic acids - Quinchlorac n) Sulfonyl ureas - Bensulfuron, chlorimuron, chlorsulfuron, sulfosulfuron, nicosulfuron, halosulfuron, bensulfuron methyl o) Thio carbamates - Butylate, Diallate, molinate, pebulate, thiobencarb, triallate p) Dithiocarbamates - Benthiocarb q) Triazines - Ametryn, atrazine, prometryn, simazine, metribuzin r) Uracil = Bromacil, terbacil, lenacil s) Urea derivatives - Monuron, diuron, linuron, methabenzthiazuron, metsulfuron, isoproturon, siduron t) Unclassified- Amitrole, anilophos, benazolin, endothal, fenac, pyrazon, vorlex, DCPA, MH On the basic of physiological response to crop plants a) Non systemic (contact) herbicides- These herbicides will act on plant tissue which come in direct contact with them. Example – Paraquat, diquat chloride, bomoxynil, ioxynil b) Systemic (translocated) herbicide - Translocated herbicide moves within plant of treatment to other plant parts. It kills the entire plant after their absorption only through a portion of plant was treated with the herbicide. Example –atrazine, 2,4-D, MCPA, MCPB, butachlor, pendimethalin, trifluralin, fluchloralin, oxadiazon, chlorimuron ethyl, bensulfuron methyl, diuron, gyphosate- ammonium On the basis of selectivity c) i. Selective herbicide - The chemical kills the targeted plant species in a mixed plant population without causing harm or slightly affecting the economical vegetation. It is considered as great single factor that helped chemical weed control so successful. 25

Ex- 2, 4-D, butachlor, alachlor, pendimethalin, fluclortion, atrazine, diuron, pretilachlor, sulfosulfuron, bromacil, uracil, triallate etc. ii. Non selective herbicide - A nonselective herbicide kills the entire vegetation without regard to species when applied to mixed flora Exmple – paraquat, diquat, chloride, gyophosate, gyfosignate, ammonium On the basis of time of application Based upon time of application Herbicides ore divided into four groups a) Preplanting herbicides - Herbicides are applied before the sowing in order to kill the heavy growth of weeds to facilitate easy seed bed preparation .The total killers are used for the purpose. Ex paraquat , glyphosate and glufosinate. a.

b.

c. d.

Pre-plant incorporation - The herbicides are applied before the planting of crop in the field. They should be incorporated to the field as they are volatile in nature Ex. Fluchloralin, trifluration. Pre-emergence - The herbicides are applied before the emergence of weeds. Soil with adequate moisture is required for movement of herbicide in to soil depth. Ex. – Atrazine, pendinmethalin, alachlor, oxyfluorfen, oxadiazizon, butachlor, pretilachlor etc. Early post-emergence application - The herbicides are applied shortly after crop emergence. Post emergence - The herbicides are applied after the emergence of weeds and crops. These chemicals act as translocated and contact killers Ex. MCPA, MCPB, 2,4-D, 2,4,-DB, isoproturon, bromoxynil

EXERCISE - 10 Weed sampling and vegetation analysis Instructional objectives The student will be able to - learn about various methods of weed sampling - determine quantitative estimates of weed cover Relevant information The quantitative determination of weed cover provides on accurate estimation of weed control for a particular environment and condition. A visual estimate of permanent weed control is normally performed for most weed control experiments. The quantitative evaluation of weed cover could provide an accurate estimate of any weed control practices. For this different sampling methods are used to obtain precise quantitative data. The sampling techniques of weeds are divided in to two groups such as destructive and non-destructive methods. In the destructive method, the weeds are uprooted for recording the plant biomass of fresh or dry weight. The dry weight of the plant is more reliable as 26

the fresh weight varies depending upon the moisture content. Under non-destructive method, samplings are done without destroying the weeds. In both the methods, quadrates are used for weed sampling. Procedure Select a field where the various weed management practices have been used. The instructor will assign the sampling size to different groups. Use the quadrate samplings for the determination of the following quantitative estimates. Two methods are used for sampling in quadrate method. The quadrate is a square area of varying sizes. Since the sampling unit is a quadrate it is popularly known as the quadrate method. In this method the sampling area is demarcated in the field for the purpose of detail weed study. (a) List or census quadrate method - In this method, individual weed species are listed and actual number of species per unit area is counted. It is easier to account the number of annual weed species. Rather, the rooted sprouts of individuals are considered as individual number in case of weed species which propagate by vegetative means. Care should be taken to count the species which roots remain with in the quadrates only. This method given accurate assessment of abundance of species. (b) Clip quadrate - The weed species in the quadrate are clipped off at the soil surface and oven dry weight is recorded. Weed vegetation analysis Some of the indices are used to assess the weed vegetation quantitatively in a particular place. ANon-destructive method. (a) Weed density – Count the number of individuals of a particular weed species per unit area and determine the relative density. Density (D) = Total number of weeds in all quadrate X 100 Total number of quadrates used Relative density (RD) = Absolute density of a weed species X 100 Total absolute density of all weed species (b) Frequency - Record each weed species that occurs in each sampling quadrate and also record the total number of quadrates being used. This measurement will determine the degree of dispersion of a given weed species in an area. Frequency (F) = Quadrates of occurrence of a species X 100 Total number of quadrates used Relative frequency (RF) = Frequency of a weed species X 100 Total frequency of all species (c) Dominance - Weed dominance refer to the ground coverage of a given species in relation of density (number/m2) of the species. Dominance - Average base area of a weed species X density Relative dominance = Total base area of a given weed species in all quadrates X 100 Total basal area of all weed species in all quadrates 27

(d) Weed abundance - Count the number of individuals for all weed species in an unit area in a given field and use the following formula. Abundance = Total number of a species in all quadrates X 100 Total number of quadrates in which species occurred Relative abundance = Abundance of a given species X 100 Total abundance of all species B. Destructive method: Weed biomass - Weed biomass production (fresh or dry weight) can be used to correlate the competitive effects of a weed on a crop yield loss. Take weed samples from quadrates and record dry weight of the samples. Determine the relative dry weight using the formula. Relative dry weight = Dry weight of a given weed species Total dry weight of all species. Results: Record all available data carefully. Include each individual weed species. Calculate all possible quantitative estimates from the field data of all groups. EXERCISE - 11 Herbicide formulation Instructional objectives The students will be - acquainted with different herbicide formulation available in the market Relevant information Herbicides are the chemicals used to kill or suppress the weeds. The biological efficacy of a herbicide depends on the type of formulation. Formulation is the process in which the active ingredients are made to commercial product by mixing with liquid and dry diluents by grinding and or by addition of emulsifiers stabilizers and other formulation adjuvants. Active ingredient is the real chemical substance responsible for herbicide effects. Materials required Herbicide containers bearing labels, sample labels of various commercial herbicides. Procedure Follow the teacher – Read the information on the labels attached to the herbicide containers. Types of formulations The formulations can be of several types. However the followings are used frequently. 28

a) Emulsifible concontrate (EC) - It consists of the active ingredient dissolved in an organic solvent with sufficient emulsifier added to create on oil in watrer emulsion. Emulsion is mixture of liquid suspended in another liquid like fat globules in milk. The umulifiable concentrates when added to water form opaque or milky solutions. Ex. Alachlor, butachhlor, pendimethalin, oxadiazon, oxyfluorfen, pretilachlor, fluchlorlin, 2,4D Amine salt.. b) Solution concentrate (SC) - In soluble concentration the active ingredient is dissolved in solvent system to provide a concentrate that is soluble in the water. Ex. MCPA, glyphosate, paraquat. c) Wettable powder - It contains finely divided solid particles of size less tham 3 microns which are suspended in water in the form of suspension. Wettable powders are divided into 3 groups. Formulation with high content of active ingredient of 60 to 90%, with medium content 30- 60% and low content below 3 % (most widely used). Ex. Atrazine, oxadiargoyl, simazine, pyrasolulfurn, sulfosulturon, linurun, diurnon, prometryn. d) Soluble powder (SP) - It is similar to wettable powder except that the technical ingredient as well as diluents and formulative adjuvants are completely dissolved. Soluble powders look like wettable powders but they form a true solution when added to water unlike suspension in case of latter. Few formulations of this type are available because few active ingredients are highly soluble in water. e) Flowable concentrate (FC) = Flowables are liquid extension of wettable powders. They are copncentrated aqueous dispersible herbicides that are insoluble or nearly so in water. They contain tile or organic solvent, an emulsifying agent and a suspending agent. The FC are easily dispersed in water and easy to measure. Ex. Bensulfuron methyl. f) Granules (GR)- The active ingredient are incorporated in particulate solid carriers suitable for direct field application. In granule formulation the active ingredient is mixed with or coated on inert carriers of appropriate size of a granulated sugar. Ex. Butachlor, alachlor g) Fumigants- Fumigants are volatible chemicals applied in confined spaces or in soil to produce a gas that will destroy weed seeds and will act as a soil sterilant. They are often injected as pressurized liquids a few inches below the soil surface Ex. Methly bromide, methane, carbon disulfide, and tetra chloro ethane. EXERCISE - 12 Idenfification of herbicide Instructional objectives The student will be able to -

study, identify and acquaint with common herbicides available in the market.

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Relevant information Herbicides differ in their properties and characteristics among different groups. Herbicides also differ in their dose, killing effect, phytotoxicity, crop safety, cost, colour, ecosuitability, persistence of residues in the soil and crops, formulation, method and time of application, mode of action and chemical composition. It is therefore, necessary that one should know the details of herbicides and will able to select proper herbicide with appropriate time, method and dose of application to manage weeds in various crops. Material required i. Herbicides container bearing labels ii. Sample labels of various types of commercial herbicides Procedure Follow the teacher. Read the information on the labels attached to the herbicide containers. Record the information in systematic manner. Observation The student will record the following observations in tabular form indicating common name, trade name, formulation and manufacturing company. Identification of herbicides

Common name

Trade name

Formulation

Acetachlor Acifluorfen Alachlor Ametryn Anilophos Anilophos Benthiocarb Butachlor Butachlor Butachlor Butachlor Butachlor Butachlor Bensulfuron methyl Clodinafop Chlorimuron Ethyl Clomazone Chlorosulfuron

Mon-8436 Blazor Lasso Ametrex Arozin Aniloguard Saturn Delchlor Hiltachlor Teer Machete Weed kill Machete Londax Topic Kloben Command Glean

90 EC 90 EC 50 EC 50WP 30 EC 30 EC 50EC 50EC 50EC 50EC 50EC 50EC 5G 60 DF 15 WP 10 WP 50 EC 75WP 30

Manufacturing company Monsanto BASF Monsanto Rallis India Ltd Aventis Gardha Chemicals Pesticide India Ltd Coromondal, Indag HinnustanIndia Ltd Herbicide India Monsanto Sudarsan Chemicals Monsanto Dupont Syngenta Dupont Nagarjun Chemicals Dupont

Cyclosulfomuron Cyhalofop butyl Dalapon Dichlofop methyl Diquat Diuron Diuron

Invest Clincher Hexapon Illoxan Reglone Karmex Hexauron

10WP 10 EC 85 WP 28 EC 24 AS 80 WP 80 WP

Fenoxaprop-P-Ethyl Fenoxaprop-P-Ethyl Fenoxaprop-P-Ethyl Fluazifop-P-butyl Fluchloralin Glufosinnate Ammonium Glufosinnate Ammonium Glyphosphate Glyphosphate Glyphosphate Imazapic Imazathapyr Isoproturon Isoproturon Isoproturon Isoproturon

Whip super Puma super Rice star Fusilade Basalin Basta Liberty Round up Glycel Weed off Cadre Pursuit Arelon Nocilon Toklan Isoguard

10 EC 10 EC 15 EC 9 EC 45 EC 15 SL 15 SL 41 SL 41 SL 41 SL 25 AS* 10 EC 75 WP 50 WP 50-75 WP 75 WP

Lactofen

Cobra

24 EC

Linuron Linuron Methabenzthiazuron Metoxuron Metoxuron

Lorox Afalon Tribunil Dosanex Invest

50 WP 50 WP 70 WP 80 WP 80 WP

Metribuzin Metribuzin Metsulfuron methyl

Sencor Tatametri Algrip

70 WP 70 WP 20 WP

Napropamide

Devrinol

45 EC

Oxadiargyl

Topstar

80 WP

United Ltd BASF

Oxadiazon

Ronstar

25 EC

Rhone & Poulene

Oxyfluorfen

Goal

23.5 EC

Indofil Chemicals

Oxyfluorfen

Oxygold

23.5 EC

De Nocil

31

BASF De-Nocil BASF Bayer (India) Ltd Zeneca Agrochemicals Dupont Bharat Pulvererizing Mills Bayer India Ltd Aventis India Ltd Hoechest Syngenta BASF Hoechest, Bayer Aventis India Ltd. Monsanto Excel De-Nocil BASF Cynamide India Ltd Dupont, Gharda De- Nocil Aventis Gharda Chemicals, Bombay Valent, Aventis Dupont Hoechest Bayer Sandoz India Ltd Gharda Chemicals, Bombay Dupont, Bayer Rallis India Ltd Dupont Phosphorus

Paraquat di chloride

Gramaxone

24 SL

Zeneca

Paraquat di chloride

Uniquat

24 SL

Pendimethalin

Stomp

30 EC

United Phosphorus Ltd Cynamide India Ltd

Pendimethalin

Panida

30 EC

Nagarjun

Pendimethalin

Dhanutop

30 EC

Dhanuka

Pretilachlor

Rifit

50 EC

Nagarjun Chemicals

Pretilachlor

Rifit

50 EC

Dhanuka

Prometryn

Prometryx

50 WP

Syngenta

Prometryn

Gesagard

50 WP

Rallies India ltd

Propanil

Stamp F 34

30 EC

Rhom and Hass

Pyrazosulfuron ethyl

Sathi

10 WP

Quinchlorac

Facet

25 SC

United Ltd BASF

Quizalofop–P- ethyl

Targa super

5 EC

Dhanuka, Nagarjun

Simazine

Hexazine

50 WP

Simazine

Tafazine

50 WP

Bharat Pulverizing Mills Rallis India Ltd

Sulfosufuron

Leader

75 WP

Monsanto

Thiobencarb Triallate

Saturn Avadex

50 EC 50 EC

Pesticide India Ltd Monsanto

Trifluralin

Treflan

45 EC

Syngenta

Trifluralin

Flora

45 EC

2,4-D Na salt

Fernaxone

80 WP

Harcourt Brace and Company, London Herbicide India Ltd Krushi Rasayan

2,4-D Na salt

Atul

80 WP

Atul Chemicals

2,4-D Amine salt 2,4-D Ethyl ester

Agrodore Weed mar

58 EC 38 EC

Herbicide India Ltd Atul Chemicals

*AS- aqueous solution

32

Phosphorus

EXERCISE - 13 Herbicide spraying devices Instructional objectives The student will be able to -

ascertain proper handling of sprayers and familiarize with various mechanism of sprayers to increase the spraying efficiency Relevant information Agrochemicals used in crop production are applied either in solution or in granular form. Granular forms are applied though hand. Generally emulsifiable concentrates, wettable powders, soluble powders, water soluble concentrates and flowable concentrates are applied though carriers. The carrier is a solid or liquid material used to increase the volume of a chemical compound so that it can be uniformly applied over the target area. The universal carrier of herbicide is water. Herbicides are mixed with water and applied as spray to facilitate even coverage over the area to be treated. Several types of sprayers are popularly used for spraying. Classification of sprayers: The sprayers are classified into various ways depending upon spray volume type and on the basis of working principle. i. Spray volume- On the basis of spray volume the sprayers are classified on the amount of solution required to cover one hectare of area. Type of sprayer

Tank capacity

a. Ultra low volume sprayer

1 litre

b. Very low volume sprayer

up to 60 litres

c. Low volume sprayer

60 - 225 litres

d. Medium volume sprayer

225 - 675 litres

e. High volume sprayer

more than 675 litre

ii. Types of application in relation to volume of sprayers: Type of application

Type of sprayer

Soil application

Medium low volume sprayer

Contact application

high volume sprayer

Systemic type application

Low and medium translocated sprayer 33

iii. On the basis of working place sprayers are divided into two groups - Ground sprayers and aerial sprayers. Gound sprayers Ground sprayers work on the ground –They can be further be divided as follows. a. On the basic operation of sprayer: a .1. Hand sprayer- It is used for spot treatment, small area and experinmental area. a. 2. Foot sprayer- It is used to cover larger area as well as for spot treatment. b. On the basis of sprayer boomb. 1. Boomles sprayer - It is generallty used in road sides along the fenced road, irrigation channel, ditch land etc. In this sprayer, there is least chance of drift hazards. b. 2. Boom sprayer - Boom are fitted in high volume sprayers which are generally used for complete coverage of large area c. On the basis of power used c. 1. Tractor operated sprayer c. 2. pump/ paddle pump sprayer c. 3. Hand operated knapsack sprayer Aeriel sprayers 1. Aeroplane or helicopter operated sprayer 2. Motor operated spryer 3. Manully operated sprayer. EXERCISE - 14 Study of sprayers Instructional objectives The student will - be acquainted with different types of sprayers. Relevant information Sprayers are of two types; hand operated and power driven sprayers. Hand operated sprayers:

34

i) Knapsack sprayers - The knapsack sprayers are loaded on the back of the applicator. During the spraying usually they carry metallic tank but plastic tanks are also used in to reduce the weight. Three types of knapsack sprayers are available (a) hydraulic (b) manual pmeumatic and (c) motorized pneumatic a) Hydraulic knapsack sprayers - It works under hydraulic pressure. The tank capacity varies from 5 to 15 litres with the provision of mechanical agitation of the spray liquid. The operator operates the lever with his left hand and pumps the spray liquid in to the lance held by his right hand. While operation it is usually possible to deliver the spray at almost constant pressure. The hydraulic knapsack sprayer could spray at 3 to 5 kg/ cm2. This sprayer is of low cost, easy to maintain and is a small holding farmer sprayer. It is more suitable for spot and band application of herbicides. b) Pneumatic or compressed system knapsack sprayer - This sprayer does not require pumping during spraying and is not pressurized before loading on the back of the worker. It is filled up as per the capacity of the sprayer. Then it is pumped either with a built in pump or from an external source like a charge pump or carbon dioxide cylinder. The main disadvantage of this sprayer is that uniform delivery pressure can not be maintained due to decreasing spray pressure during the spraying operation. This may cause uneven spray. It is more useful to spray in hilly terrain or irrigated fields where walking is difficult. The cleaning of the tank is difficult as the mouth of the sprayer is very small.

c) Motorized pneumatic sprayer - It is a low volume sprayer suitable for spraying concentrated spray liquids. A blast of air acts as a carrier of herbicide concentrates in these sprayers which are called blowers. The air is forced through the spraying jet of the delivery hose of the blower and the nozzle tube ejects the spray liquid. In this blast the air blast atomizes the spray liquid into tiny drops. In this sprayer air acts as a carrier. The atomization is more vigorous when the air is pumped at faster rate in to the spraying unit .The herbicide is lost as spray drift as the blower produces the droplet size of 50-100 microns. This blower is called as mist blower. The main advantages of knapsack blowers are low volume spray resulting in reduction in loss of time in refilling the tank ii) comfortable working and (iii) fast spraying. The discharge of a blower is about 0 3-0.2 liter per minute which can be regulated with dosage sleeve. It has a swath of 7-8m .There is requirement of 60 litres of spray liquid for spraying of one hectare of Land through knapsack blowers. In this regard the applicator has to walk fast to keep pace with it discharge. Low volume spraying with blowers is not as uniform as with high volume sprayers. The knapsacks are more preferably used for spraying of short translocated type of herbicides. ii) Foot sprayers - Foot sprayers are used for application of herbicides in larger holdings. The pump lever of a foot sprayer has a pedal. The lever is conveniently worked with a foot. The pedal pump sprayer has an external spray tank through an intake pipe fitted with a sieve at its sucking end. The working pressure may range between 17 to 21kg/cm2. Foot sprayers have provision of long delivery hoses fitted with a lance. The suction spout is 35

dipped in a container filled with herbicide spray solution which acts as a source of external tank. Power driven sprayers The tractor mounted power driven sprayers work under a spray pressure of 1.4 to 2.8 kg/cm2. These are fitted with multi nozzle boom which make them useful herbicide application equipment for the large holding farmers. The flowing and wide angle or reduced pressure cone nozzles should be used in pre-emergence application. Flat fan nozzles are suitable if drift is not a problem and the boom is maintained at constant height. The flat fan nozzles mounted at proper height will provide uniform weed control. Flat fan or holder cone nozzles are suitable for post emergence spray of herbicides. The flood jet deflecting type of nozzle provides the lower penetration of canopy than the flat fan and holler cone nozzle. The main advantage of tractor mounted sprayer is high uniformity of spray. But the drawbacks are the high equipment cost and high level of skill required to operate it. The success of tractor mounted sprayers depends on proper calibration of the sprayers and its boom adjustment to avoid over lapping and gappy sprays. The spray pattern should be so developed as to obtain a uniform spray. For directed spraying the nozzles falling on crop rows are turned off and the boom height is so adjusted as to avoid the crop plants and spray the weeds. The tractor mounted sprayer fitted with a tilted boom is used to spray total weed killers on road side weeds. Now a days a recirculating type sprayer has been developed in which the excess herbicide from nozzles that spray across the crop row is collected in recovery boxes. The excess is then returned to the spray tank for reuse. This type of sprayer is used in treating the specific weeds that grow taller than the crop rows.

iv) Aerial sprayers - Aerial application of herbicides is limited to treat the weeds in stretches of aquatic bodies and very large continues land occupied by single crop or areas under undesirable plants. The spray drift is the main limitation of aerial sprayers. (v) Hand held sprayers - The hand carried lighter weight low volume battery operated sprayers are suitable in smaller holding size of the farmers of tropical and subtropical countries. Two types of such spray are available to the farmers. (a) Vibrajet - The vibrajet sprayers with the discharge rate of 100-200 litres/ha designed to produce coarse spray of mean droplet diameter of 4.55 ml and above are drift resistant. It is suitable to apply herbicide solutions and emulsions but not suspensions. In vibrajet, the spray liquid is fed to special type of spray nozzle with a multi hole sleeve by gravity flow. The liquid reacting there is put to fast oscillatory action produced with a 12 volt battery operated motor. It breaks the solid stream of liquid into large droplets before it leaves the nozzle orifice. Vibrajet type of sprayers hold good in areas prone to spray drift hazards. 36

(b) Controlled Droplet Applicator (CDA) – In this controlled application the spray droplet size is 250 microns. This droplet size is more effective on plants than the larger droplets and these are adequately drift tolerant. The controlled size droplets are known as ultra low volume sprayer. It is done using an ultra low volume sprayer. It has a rotary atomizer and a spinning disc with a serrated edge which revolves at a speed of 2000 revolutions per minute (rpm) to produce droplet size of 250 micron. The herbicide spray solution is gravity fed to the disc from a plastic container of 2.5 litres capacity. The atomizer is driven by a small electric motor which is attached to the tube carrying the batteries that provide power for the motor. The spray volume is 15-20 litres/ha. This sprayer is more handy for small holdings, treating rough topography land and wet paddy fields. The sprayer covers the swath of 1.2 m wide with a walking speed of 3 to 5 km/hr. This method is particularly useful in case of foliage applied systemic herbicides. Granular Applicator – The pre-emergency application of granular herbicides is done in the crop rows in bands. A granular applicator consists of the hopper in which the granules are placed, a rotating disc device to get the broadcast application pattern, a long flexible discharge tube with a nozzle of the distal end and a finger controlled mechanism for regulating the discharge rate of the granules. By rotating the handle the granules are released from the tube through the exit hole of the hopper. The granule applicator is made of plastic with capacity of 1 to 10 kg. It is carried on the back. The bigger type granule applicator is tractor mounted. It consists of a band distributor that applies granules laterally and uniformly over the desired band width. Exercise - 15 Study of nozzles Instructional objectives The student should be able - to know the different types of nozzles used for spraying of herbicides Relevant information The important components of a sprayer are: tank, nozzle, pump, strainer, pressure regulator and hose. Depending upon spray patterns and droplet size different types of nozzles are available. i) Cone nozzles - In this nozzle, the liquid is forced through one or more tangential or helical passages into a swirl chamber through which the liquid passes a circular orifice at a high rotary velocity to form an air cone within the orifice and swirl chamber. The liquid emerges from the orifice as a hollow or solid cone. In case of solid cone nozzle, the liquid also passes centrally through the nozzle to fill the air cone. The liquid also emerges from the orifice as a hollow cone. The hollow cone nozzles produce the heaviest droplet distribution on the edges of the pattern. The cone nozzles are used for spot application of post emergence herbicides. 37

ii) Flat fan nozzles - In flat fan nozzle the tip has a rectangular orifice behind which two stream of liquid meet because of the shape of the cone. The deepened edge flat fan nozzles are preferred for broadcast application of herbicides on flat surface. The rectangular pattern flat fan nozzles are used for band application of herbicides in row crops. The flat fan nozzles give more uniform coverage than the cone nozzles. iii) Flood jet deflector nozzles - It delivers coarse droplets of fluid spray under pressure, thus minimizing the drift hazard. It also produces a wide angle fan pattern of spray. The clogging is considerably reduced as the nozzle orifices are large. This nozzle is also used in the subsurface application of herbicides. iv) Boom nozzles - A boom is a horizontal pipe with two to several nozzles on it. These nozzles are spaced from 3o to 60 cm apart on the boom length as the distance between nozzles at two ends of the boom may vary from 1 to 15 m. Short booms with 2 to 3 nozzles are used with manual sprayers while the longer ones are attached with tractor mounted sprayers. A spray boom obviously covers in each trip a wider spray width than a lance. Vertical height of the boom and nozzle spacing on the boom can be adjusted to obtain a uniform spray. N:B:(I) It is to be mentioned that a nozzle usually has four different parts like nozzle body, strainer, spray tip and nozzle cap. Spray tip is the most important nozzle component of a nozzle because depending upon its design the flow and distribution of the spray are determined. (II) Power driver sprayers are usually fitted with a pressure regulator so as to push the liquid at a constant desired pressure. With out a pressure regulator the nozzle will deliver more liquid at one time and the less at the other in the same time. (III) Knapsack sprayers do not come equipped with a pressure regulator as it is too expensive. However, regulator valves intended specifically for knapsack sprayers can be used alternatively. EXERCISE - 16* Study of herbicide calculations Instructional objectives The student should be able to - understand the calculation of herbicide applications, volume of solution per area - learn how to calibrate sprayers - be able to apply herbicides (sprayable and granules) accurately and uniformely in the field 38

- understand the importance of accurate herbicide sprayers and equipment Relevant information Acid equivalent (a.e.) – The theoretical yield of parent acid from an active ingredient. Active ingredient (a.e.) – The chemical in a product that is responsible for the killing effects. Both a. e. and a. i. are generally expressed in kilogram (1000g) per hectare (10,000 sq. m.) for either dry or liquid formulations. Volume rate – The amount of liquid (water) applied per unit area. Why are herbicide calculations done? This is done for effective us eof chemicals for different weed control. Calculation of herbicide Formula for calculation of commercial product Weight of herbicide to be applied X 100 Percent of active ingredient Example Pendimethalin (stomp 30 EC) is to be applied at the rate of 1 litre a.i. / ha in groundnut as pre-emergence application. If the amount of water to be mixed is 800 litres/ha, calculate the actual amount of pendimethalin to be added to water/ha. Solution Amount of pendimethalin required per hectare = (1/30)x 100 = 3.33 litres. So 3.33 litre of pendimethalin with 800 litres of water will be required to spray in an area of one hectare. Example A 2,4-D herbicide has 40% acid equivalent, 45% active ingredient and 55% inert material. The recommended dose is 2kg a.i./ha. How much herbicide is required for one hectare if the quantity of water required is 800 litres per hectare? Solution Amount of 2,4-D required/ha = 39

a.i. recommended x 100 =

(2/40) x 100 = 5 litres

Acid equivalent present Calculation of acid equivalent Example Find out the acid equivalent of 2, 4-D dietharol amine salt with 70 % a.i. Acid equivalent % = a.i. molecular weight of 2,4-D acid

= (70x221) / 326 = 47

Molecular weight of 2,4-D amine salt Calculation of commercial product for band application Example Diuron (80% WP) is recommended @ 2 kg a.i./ha as per pre-emergence spray as band application. The distance between 2 rows is one metre and 20 cm band is required to be sprayed. How much is the quantity of Diuron required for band application as well as for usual overall soil application in 1000 sq. m. (rectangular shape 1 m x 1000 m) Solution Diuron required for overall soil application = (2/80) x 100 = 2.5 kg/ha = 0.25 kg/1000 sq. m. Diuron required for band application of 20 cm width = {0.25 x (20 / 100)} = 0.05 kg / 1000 sq. m. *Source: Practical Manual on Crop Production (1997), Department of Agronomy, CA, OUAT, Bhubaneswar EXERCISE - 17 Calibration of sprayers Instructional objectives The student should be able to - calculate the requirement of herbicide formulation - calibrate sprayer for uniform application - correct the operational deficiencies of a sprayer Relevant information 40

The calibration of sprayer is required for safe and effective use of herbicide. Calibration is to adjust the application pressure, application speed and to get desired volume per unit area. The area sprayed depends upon the type of nozzle, spray pressure and the speed of application. The best way to calibrate is to spray an area of known size and measure the volume of spray delivered from the tank. This may be done using different nozzles at different spray pressure and walking speeds. Care should be taken to see that speed and pressure do not vary significantly from the calibration test to actual field spraying.

Materials required 1. Knapsack sprayer 2. Measuring tape 3. Herbicide formulation 3. Water 4. Measuring bucket. Procedure Fill the knapsack spray tank with one litre of water. Generate pressure by operating the hand lever. Mark in the filled an area having width equal to swath (distance the spray falls on the ground at a fixed height). The spray lance could be hold constant while walking forward or could be swung from left to right as in case of flat fan nozzle). Carry out spraying in the marked area. Walk at a normal speed. Try to maintain uniform pressure by operating the sprayer at a constant speed. Mark the place where water is exhausted. Area covered = Swath width x length sprayed. Observation- The width of spraying i.e swath is 0.5 m and length sprayed is 40 m. Area covered = Length x width = 40 m x 0.5 m = 20 sq m Spray volume (L/ha) = ½ x 10,000 lit = 500 l/ha. The spraying should be done with same swath width and operating speed to apply the herbicides in the field. All students are to attempt spraying with different nozzles and application pressure and calculate the spray volume applied per hectare. For calibration of a boom sprayer with more that one nozzle or tractor mounted sprayer, the flow rate of all nozzles in a boom has to be taken into consideration. Making stock solution- In order to apply the herbicide uniformly in the entire area, it is advisable to prepare a stock solution of the herbicides. Example - Area to be treated = l/ha sprayer capacity = 10 l Spray calibration = 500 l/ha 41

Number of refills required to spray = 500 = 50 10 Now one can take desired quantity of herbicide and dilute it with 10 litre of water. Otherwise, one can dissolve the entire quantity of herbicide in 500 litre of water contained in a big container and use the solution directly. Problem - A person is walking at the speed of 1 km/hour covering a swath of action. (i) (ii)

Find out the area covered in an hour (time taken to spray /ha of land). Area covered (ha/hour) = Walking speed & km/hour) x m/km x spray width (m) m2/ha =

1 x 1000 x 0.5 = 0.005 ha per hour 10,000 (iii) Time required to spray 1 ha = 1/0.05 = 20 hours Problem - A person is walking at the speed of 1 km/hour covering the spray swath of 0.5 m. If 500 litre of water is sprayed in one hectare of land, find out the pump capacity. Area covered (ha/hour) = 1 x 1000 x 0.5 = 0.05 10,000 Time required to spray 1 ha = 1/0.05 = 20 hours In 20 hours, the pump has sprayed 500 litres. So

= 500

= 417 ml/minute

20 x 60 EXERCISE - 18 Method of herbicide application Instructional objectives The student will be able to - ensure the effective use of herbicide. - provide early season weed control. - save the non target vegetation from the herbicide. - reduce the weed for repeated intercultural operation during crop season. - control the seeds of closed spaced crops without transplanting. - control the seeds during adverse soil and climatic conditions. - save the economical vegetation from herbicide without any injury. - reduce the weeding cost, labour use and save time. Relevant information 42

The selection of proper method of application of herbicide is necessary for effective and efficient control of weeds. The herbicides applied to soil or to the foliage are decided basing upon their mode of action, selectivity and properties of herbicides. Environmental factors, conveyance and cost are the other factors which influence the correct method of application. Herbicides applied through improper method will give rise to ineffective weed control and severe crop injury. Method of herbicide application – The herbicide application is grouped into the following ways: (A) Method of application of soil active herbicides (a) Surface application: The soil applied herbicides are applied on soil surface where they are left as such or incorporated in to the soil. Under the influence of soil moisture or rain herbicides move to 3 to 4 cm of soil depth under the influence of rain or irrigation water. The volatile herbicides like trifluralin and fluchloralin herbicides are incorporated to the soil by light ploughing or with light irrigation to the depth of 5 cm. (b) Sub surface layering- In this method the herbicides are applied in concentrated band about 7-10 cm below the soil surface. It is very effective in controlling perennial weeds (e.g. Cyperus rotundus) by inhibiting the growth of shoots. The subsurface application is done through the special flood nozzles introduced below the soil. (c) Broadcast and band application: Broadcast application of herbicide is made over an entire area. The band application of herbicides is done on restricted area along the crop rows. This application is cost saving as it reduces the quantity of herbicides required. In the band method of application the inter rows are cultivated later to remove weeds from the unsprayed areas. (d) Soil fumigant application method – Depending upon the nature of the soil fumigant it can be applied either by(i) Soil injection (e.g chloropicrin) (ii) Releasing under sealed plastic covers (e.g methyl bromide) (iii) Soil surface application (e.g metham) (B) Method of application of foliage active herbicides(a) Blanket application- The herbicides are applied uniformly to the standing crop irrespective of the location of the crop plants. The highly selective herbicides are preferred for blanket application. (b) Directed spraying – In this method the application of herbicides is directed to weeds growing in the inter rows of the crops avoiding the crop foliage as much as possible (e.g. paraquat in sugarcane). Directed spraying is also performed by setting the nozzles low with spray patterns to intersect the base of the crop plants just above the soil line. This saves the crop plants from herbicide injury and improves weed kill. Directed spraying can also be accomplished by fitting the nozzle in the hood. Usually the selective herbicides are used in crops. But in hardy crops with greater plant height over weeds, the non selective herbicides can be applied by using nozzle attached with the hood. (c) Protected spraying - In wide spaced vegetables and ornamental plants, the non selective herbicides are applied by covering the crop plants with plastic or metallic 43

covers. This method is very laborious. But it is very effective in weeding the high value crops. (d) Spot treatment – The herbicides are applied to small patches of weeds leaving the weed free gaps untreated. Noxious perennial weeds are effectively controlled with application of potent herbicides in this method. (C) Method of treating brush and tree weeds (a) Basal bark treatment – The basal bark of the brush or tree to the length of 30 cm is peeled and herbicides are applied to the peeled portions only. (b) Cut stump treatment - The herbicide application is made on the cut surface after sawing the tree just above the ground level. (c) Frill, knotch and injection method - The frill and knotches are made with sharp tool into the tree weed at convenient height. The frill and notches are filled with herbicide. The herbicides are also injected in to the holes made in the tree trunk up to 2.5 cm thickness. These methods are adopted on thick stem trees of 8 cm or more in diameter. Girdling and frilling are methods of killing standing trees that may be done with or without an herbicide. However, the groove must completely encircle the trunk. Frilling is a variation of girdling in which a series of downward angled cuts are made completely around the tree, leaving the partially severed bark and wood anchored at the b Other methods of herbicides application (a) Direct contact application (DCA): It involves all the techniques such as wiping, rubbing and smearing of herbicides on the target plant surface. It is done by using herbicide wax bar, herbicide cloth mulch, roughing gloves or hand brush. The herbicide laden wax bars are dragged against weeds growing much taller to the crop plants. Herbicide cloth mulches are placed in the crop inter rows. The roughing gloves carry arrangement to smear herbicide on the weed gripped by the worker. (b) Soil injection: Herbicides like ethylene dibromide, carbon disulphides and vernolate are applied by soil injection at prescribed spacing before planting of crops. EXERCISE – 19 Precautions for proper application of herbicides Instructional objectives The student should be able to - know the precautions for proper application of herbicides Relevant information ♦ The spray tank should be at least one third full with clean water before any concentrate is added and the contents will mix while the concentrate is being put in slowly. ♦ Wettable powder formulation should be made up into a paste and then diluted before adding to the spray tank. 44

♦ Fill up the tank up to two third of its volume and one third volume is left for proper spraying. ♦

Pumping should stop as soon as the tank is empty and a mark should be left in the field to indicate to start the spraying again.

♦ It is worth full to divide the whole area to be treated into convenient blocks for uniform spraying for pre emergence applications. ♦ Early morning is considered ideal period for herbicide application as the wind is very gentle during that period. ♦ Spraying with desired spray width is highly required. Spraying along the rows can facilitate easy swath matching. ♦ Avoid spraying foliage active herbicides if rains area expected in the next two hours or so. However a light rain or irrigation is often beneficial for a soil active herbicide. EXERCISE - 20 Maintenance of Sprayers Instructional objectives The student should be able to - know the maintenance of different types of sprayers Relevant information  Use clean water as carrier of herbicide  Use screens at the inlet of spray tank to prevent foreign material from entering.  Never use metal object for cleaning the nozzles. It will corrode nozzles.  Flush the sprayer before use. Flush the whole sprayer with two tankfuls of clean water by spraying through the boom with the nozzles removed.  Clean sprayers thoroughly after each period of use. Remove and clean all screens and boom extensions with kerosene using a small brush.  Any blocked nozzles should be changed or washed in clean water. Do not clean the blocked nozzles with the mouth or hard objects as they may alter spray output and droplet size.  Nozzles should be checked very often and may require replacing under damaged condition.  When sprayer is to be stored, it should be thoroughly cleaned by adding detergent to the water and rinsing several times to remove all traces of the detergent before storing. The tank should be drained out and left with lid off to allow air circulation.  All bearing and hinges should be oiled or greased and wheel machines should be put on blocks with the tyres out of sun.  Hoses can be removed and stored hanging vertically to prevent rodent damage. 45

EXERCISE - 21 Study on allelopathy Instructional objective The student should be able to -find out the allopathic effect of some weed species on seed germination and crop growth. Relevant information Allelopathy refers to any direct or indirect effect of one organism on other organism through production of allelo chemicals which are volatile in nature. This allelopathy is one form of biochemical interaction between plants which is totally different from competition. Materials required (i) Dry plant materials- Cyperus rotundus, Parthenium hysterophorus, Celosia argentea. (ii) Funnel (iii) Filter paper, petridises (iv) Crop seeds - rice, maize, green gram. Procedure Weigh 199 gram of dry seed residues and soak it over night with 100 ml of distilled water. Filter the contents. Prepare solutions such as 1:1. 1:2, 1:4 etc by diluting with distilled water. Add 10 ml of the extract in each petridis containing crop seed. Keep the dishes in an incubator adjusted to appropriate temperature. Similar experiments can be conducted in pots with direct application of seed residues to the soil. Use plant residue at 1, 2, 3 and 5% (W/SO) and mix with soil properly. Sow the crop seeds. Observation Observe the germination of seeds at periodic interval for petridis experiments. Measure the radical and coleoptiles length of each samples. Observe the emergence for the experiment with soil in pots. Finally record the overall growth of each species. Tabulate the data and draw a line graph for each species.

46

EXERCISE - 22 Weed Seed Dormancy Instructional objectives The student should be able to - study the different weed species possessing dormancy. - find out the environmental and biotic factor that influence seed dormancy. Relevant information Weed seeds differ widely in their viability, germination and persistence. Many weeds germinate immediately after harvest of a crop while others remain dormant over a length of time. The dormant seeds do not germinate even if favourable conditions for germination are provided. Weed seeds have 3 types of dormancy such as enforced, innate and induced. Enforced dormancy is due to absence of germination factors like moisture, red light, temperature and CO2. Innate dormancy is a genetically controlled character and inherited. Innate dormancy results from the presence of hard seed coat, rudimentary embryo, physiologically immature embryos and germination inhibitors. Induced dormancy develops when the non-dormant seeds are exposed to certain environmental condition like increase in temperature and carbon dioxide content, low oxygen content and water logging in soil. Materials required i. Seed of melilotus ii. Sand paper iii. Sulphuric Acid iv. Potassium nitrate Procedure Take 20 gram of seed and place it on a sand paper. Scarify the seed coat of Melilotus indica seeds. Put the seeds on a moist filter paper in petridis after scarification. Again take another 20 gm of seeds without scarification and put the seeds in petridis. The second lot of seeds will act a control. Place the petriplates in a BOD incubator or germinator set at 15-20 oC. Set up another experiment with melilotus seeds treated with KNO3. Results: 47

Observe germination of seeds and count the number of seeds germinated. Take a final count after 15 days. Observation 1. 2. 3. 4.

Plot the germination percentage of seeds against time on a graph. Explain the germination results based on each experiment. Observe the type of dormancy. EXERCISE - 23 Depth of weed Seed Germination

Instructional objectives The student should be able to - demonstrate that seeds of different species have varying ability in relation to depth of soil from which they can germinate. - establish the influence of seedling depth on time of germination. Relevant information Weed seeds differ widely in their size, shape, viability and persistence. Many of the weed seeds germinate immediately after harvest of crops while others remain dormant for a long period. Weed seeds also germinate from a greater depth of soil. But majority of them germinate from the surface soil. Seedling vigour and subsequent growth of the seed depends upon the time and depth of germination. The germination of the weed and seedling emergence plays an important role in early crop weed competition. Materials Required i. Green house soil (Loam soil, coarse Sand, peat soil). ii. Plastic pots, paper towels, labels, measuring stick. iii. Crops seeds- Rice or wheat or mung. iv. Weed seeds – Horse purse lane, barnyard grass and crows foot grass. Procedure Students will be allotted to different groups. Each group will work on treatments assigned by the instructor. Rice with barnyard grass, wheat with crows foot grass and mung with horse purse lane are sown in the ratio of the crop seed to weed seeds of 25:25. Both crop and weed seeds are sown at the depth of 0, 1, 2, 4 and 6 cm below the soil surface. Each treatment is to be replicated three times. For sowing in required depth fill the soil is the pot and packed and gently. Use the marker for measurement. Sow the seeds uniformly in the pot. Fill the pot with soil to the middle of the pot. Pack gently and add more soil as 48

required to achieve the current level. For 0 cm depth of sowing make sure that the soil is lightly formed. After sowing the seed, label all the plots fully and place in green house. The pots are watered regularly for germination. Observation Observe germination in terms of number of seedlings emerged. Relate these number in relation to depth of sowing. Observe relative seedling vigour from seeds at different depths. The germination is to be counted in each and every day and data are recorded. Make line graphs on % emergence against time. Each graph should be for single species but show all depths. A second graph showing final % emergence (4 weeks after planting) vs depth should be compared for all the species.

EXERCISE – 24 Crop Weed Competition Instructional objectives The student should be able to - study the competitive effects of weeds on crop growth. - know that different crops differ in their ability to compete and that plants compete with one another. Relevant information Weeds compete with crop plants for light, space, water and nutrients. The resultant effects are reduction in stand, vigour and yield. Thus, elimination of weed competition during critical period is necessary for optimal growth and yield of crop. Materials required i. Plastic tray ii. Soil iii. Crop seed iv. Weed seeds (Barnyard grass) v. Paper towels vi. Weighing balance Procedure Students will work in assigned groups. The instructor will allocate each group their particular treatments. Cover the bottom of the tray with a layer of paper towel. Fill the 49

tray up to ¼” from the top with green house soil mix. Sow 25 rice seeds in each tray. Pour weed seeds of barnyard grass as per treatment of 0. 40, 100 and 200 per tray. Cover the seeds with a thin layer of soil and water regularly.

After emergence maintain crop weed ratio of 1:0, 1:1, 1:2 and 1:4 by thinning. Repeat the same exercise for sunflower crop. Maintain 3 replications for each treatment. Observation Observe the experiment in each week. Both the crop and weed species will be harvested after 6 weeks of growth. Record the fresh weight and dry weight of weeds along the weed count in every week. The height of crop and weeds are to be recorded. The results of all groups will be tabulated and discussed. The data on mean weight of each species per tray and the mean weight per plant of each species is recorded. It will give estimation about the impact of weed density on crop growth and the crop competitiveness with weed. EXERCISE - 25* Evaluation of herbicide application Instructional objectives The student should be able to -

know various methods of herbicide evaluation visualize the effects of various herbicides in inhibiting germination and growth of weeds and crops Relevant information Is evaluation of herbicide application necessary? Due to improper application, herbicide treatment may be ineffective or it can cause serious damage to crop in which it is applied or to trhe neighbouring crops. For safe and effective use of herbicides, the evaluation of herbicide application to weeds and crops is necessary. Evaluation methods : Two types I. Quantitative method: count the number of weeds per unit area (specieswise). Take the weight of samples and yield of crops. Yield may be grain, straw etc. This Method is quite accurate but is time consuming. This is done as follows: a. Based on weed index (WI) Weed index = (X-Y) / X x 100 Where, X = Yield from weed free hand weeded plot 50

Y = Yield from treatment plot Lesser the weed index, better is the efficiency of the herbicide. b. Based on weed control efficiency (WCE) weed control efficiency = (X –Y) / X x 100 where, X = dry matter production of weeds in unweeded plot Y = Dry matter production of weeds in treatment plot. II. Qualitative method This method follows arbitrary scales to measure the percent control (stand reduction) and growth reduction of the surviving crop plants. Crops and individual weed species may be rated separately. The European Weed Research Council Rating system Weed response Rating 1 2 3 4 5 6 7 8 9

% Weed control 100 99.0 - 96.5 96.5 – 93.0 93.0 – 87.5 87.5 – 80.0 80.0 – 70.0 70.0 – 50.0 50.0 – 1.0 0.0

Verbal Description Completely destroyed Very good control Good control Satisfactory Just satisfactory Unsatisfactory Poor Very poor As untreated

Rating 1 2 3 4 5 6 7 8 9

% Crop Injury 0.0 1.0 -7.0 3.5 – 7.0 7.0 – 12.5 12.5 – 20.0 20.0 – 30.0 30.0 – 50.0 50.0 – 90.0 100.00

Verbal Description No reduction or injury Very slight discolouration More severe but not lasting Moderate and more lasting Medium and lasting Heavy Very heavy Nearly destroyed Completely destroyed

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As regards toxicity to crop, usually the toxicity is reflected in grain yields or if the toxicity is apparent, counts of crop plants at different stages of crop growth will give a clear picture of the toxicity to the crop. *Source: Practical Manual on Crop Production (1997), Department of Agronomy, CA, OUAT, Bhubaneswar EXERCISE – 26 Phytotoxicity symptoms of herbicides Instructional objective The student will be able to -

learn the symptoms of phytotoxicity of herbicides in different crops

Relevant information A chemical is of little use if it injures the target crop or persists in soils for very long periods of time in areas where extensive crop rotation schemes are practiced. many times herbicide injury may be exhibited on susceptible species due to off-site drift of spray material or vaporization. Although isolated cases of herbicide injury may occur when labeled practices are adhered to, most herbicide injury occurs whenever certain errors in rate calculations, spray calibration, chemical selection, drift of sprays or when unusual soil or climatic conditions exist. When herbicide injury does occur, diagnosis is often difficult and somewhat confusing since the symptoms of injury may vary depending on the herbicide, plant species, environment, time or method of application, and stage of growth of the plant. In addition, nutritional problems, physiological disorders, diseases, nematodes, and insects may often cause similar injury to certain herbicide families. Many herbicides can be classified into certain families of chemistry which often exhibit similar injury symptoms. Even if you are not familiar with a particular herbicide, you may be able to recognize the symptoms by knowing general injury characteristics that a herbicide exhibits. General symptoms of herbicide injury are given and may be of help in eliminating certain herbicide families as the probable.

Sl. No.

Herbicide Phenoxy and pyridinoxy Auxin-type herbicides

Symptom Stem twisting Stem swelling Stem twisting Stem and leaf reddening Leaf curling and 52

Crop Cantaloupe Cotton seedling

lettuce

Dinitroaniline herbicides DNA’s Nitrile herbicides Glyphosate

cupping Leaf strapping Buggy whipping

cowpea (on corn) (on cotton) cotton

Bipyridilium herbicides Paraquat

Chlorotic mosaic Immediate cessation of growth Stacked nodes (regrowth) Interveinal chlorosis Necrosis New growth unaffected Leaf tip burn, Necrotic lesions

cotton

Diphenylether herbicides Goal (oxyfluorfen) -

Necrotic spots with red halo Bronzing of contacted leaf tissue

Triazine herbicide

Cotton, cowpea

Corn

cotton

Triazolinone Aim (carfentrazone) herbicides Imidazolinone herbicides

Bronzing and necrosis of leaf tissue

Watermelon and cotton

Buggy whipping

Corn Watermelon Cotton

Sulfonylurea herbicides

Stacked nodes Lime green color, Cupping of upper leaves Red veins

Pyrimidinyl oxybenzoate herbicide Aryloxyphenoxy propionate and Cyclohexanedione herbicides

Red veins

Cotton and alfalfa cowpea

Growing point easy to remove

corn

Purpling of leaf tissue

grain sorghum

Sulfonylurea herbicides

Red veins

cotton and alfalfa

Pigment inhibiting herbicide Evital (norflurazon) -

Bleached leaves

corn, Johnson grass, cantaloupe, morningglory, and purslane

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Phyto toxicity of herbicides can also be classified as per the mode of action of the herbicide as given below. 1.

Classification as per mode of action

Herbicides in this group

Symptom

2.

Growth Regulators

2,4-D ,2,4-DB,Cloypalid, Dicamba, MCPA, MCPP, Picloram, Triclopyr

Twisted, malformed leaves and stems, callus-like growth on young woody stems

3.

Photosynthesis Inhibitors

Yellowed, chorotic leaves which may turn necrotic

4.

Pigment Inhibitors

Atrazine, Bromacil, Cyanazine, Diuron, Linuron, Metribuzin, Prometryne, Simazine, Tebuthiuron Amitrol, Clomazone, Fluridone, Norflurazon

5.

Amino Acid Synthesis Inhibitors

Chlorsulfuron, Glyphosate, Imazethapyr, Pyrithiobac, Sulfmeturon, Sulfosate

Many symptoms including stunting, chlorosis, reddening, and distortion of terminal growth

6.

8.

9.

10.

11.

Albino or bleached appearance to foliage

Inhibitors of cell Benefin, Bensulide, Divisionin DCPA , Dithiopyr , seedlings Napropamide, Oryzalin, Pendimethalin, Prodiamine, Pronamide, Thiazopyr, Trifluralin, Inhibitors of Both Alachlor, Butachlor, Shoots and Roots of Metolachlor seedlings

Stunting and swollen growth tips, sometimes swollen stems.

Cell Membrane Disrupters: Oils, Acids and Salts

Oils, acids, salts

Water soaked appearance followed rapidly by necrosis and death of the sprayed plant

Diquat, Paraquat

Water soaked appearance followed rapidly by necrosis and desiccation of leaves and stems Necrosis of leaves and stems

Cell Membrane Disrupters: Bipyridylium Herbicides Cell Membrane Disrupters: Diphenylether Herbicides

Acidfluorfen, Lactofen, Oxyfluorfen,

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Stunting and distortion of seedling or developing leaves

EXERCISE - 27* Weed survey Instructional objectives The student should be able to - gain knowledge on the type of weed flora present in a region - know how various factors influence occurrence of weeds Relevant information Weed survey gives a blanket idea about the weeds present in a region. The occurrence of weed is largely influenced by climatic (rain fall, light, temperature, wind and humidity), edaphic (soil pH, soil fertility, soil water, soil aeration), biotic (plant, animal, parasitic weeds, allelopathic effect) factors. Further, chemical weed control mainly depends on the type of weeds present in a particular crop. Hence, for proper management of weeds one must perform the survey of weeds in an area. Materials required 1. Conveyance to visit area 2. Note book to note the information Procedure After reaching the site, select farmers randomly. Take atleast 10 minimal sample area of size 0.25 m x 0.25 m or 0.5 m x 0.5 m or 1.0 m x 1.0 m as per convenience with a piece of string and identify the weeds and count . Collect data in the same way in different seasons as per the proforma B. collect secondary information of the area surveyed as per proforma A. prepare the report with all the details. Sl. No.

Particulars

Date of observation

1.

Village

:

2.

Subdivision

:

3.

District

:

4.

Name of the farmer

:

5.

a.

Total area of the farmer

:

b.

Name of the standing crop

:

55

c.

Name of the previous crop

:

d.

Crop rotation followed

:

e.

Tillage practices followed

:

(i) preparatory cultivation

:

(ii) after cultivation

:

Survey area details

:

Cultivable/ fallow/ forest

(a)

Appearance of the site

:

Waste land/ road side / pasture/ marshy land/ tank/ river

(b)

Soil

:

Shallow/ medium/ deep

(i) Type

:

Red/ black/ alluvial/ lateritic

(ii) Texture

:

Sandy/ loamy/ clayey

(iii) Soil reaction

:

Acidic/ alkaline neutral

(iv) Soil depth

:

6.

(v) calcareous or non calcareous

:

(c)

Source of manures and fertilizers

:

(d)

Season

:

(e)

Irrigation

:

(f)

Any other information relevant

:

Signature of the overseer

:

56

FYM/ compost/ sheep penning/ poultry or pig manure/ gree manuring/ green leaf manuring/ chemical fertilizers

Well/ tank/ canal/ river

PROFORMA - B Survey of weeds Sl. No. 1.

2.

3. 4. 5. 6.

Particulars Sedges Cyperous rotundus C. difformis C. iria Fimbristylis miliacea Intensity (no./m2) Relative intensity (%)

Remarks

(No. of sedges/ total no. of weeds) x 100

Grasses Echinochloa crusgalli E. colonum Digitaria sanguinalis Dactyloctenium aegyptium Intensity: Relative Intensity: Broad leaved weeds Aquatic weeds Parasitic weeds New weeds to be identified

Calculation The student should count the weed species present separately from all the 10 sample areas and find out the mean weed population species wise by averaging the data taken over the 10 sample areas. Then calculate the relative density of each type of weed species in the following way: relative density (%) = (Number of weeds/ Total number of weeds) x 100. This gives an idea about the dominance of a particular weed species in a particular area.

*Source: Practical Manual on Crop Production (1997), Department of Agronomy, CA, OUAT, Bhubaneswar

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