Weed competition is a major limiting factor for the productivity of crops. Weed control is one of the main concerns in organic farming. Weed depletes nutrient, water and light their by reducing crops yields drastically. The chemical intervention is not permitted for weed control purpose in organic farming system. Apprehension regarding the consequence of managing weeds without the use of herbicides is a major factor limiting the adoption of organic farming by conventional growers. As wide spread application of herbicides has led to concern about contamination of environment, residues problems in soil and water, toxicity to animals and appearance to resistant weeds. The elements to consider in controlling weed problems are only the non chemical methods of weed control. These include physical /mechanical, cultural and biological methods of weed control.

1. 1

2. Weed Management in Organic
crop production
BASAVARAJ PATIL
PGS13AGR5974
II Ph. D
Dept. of Agronomy
2

3. Overview of seminar

4. Organic farming:
“Organic agriculture is a production system that sustains
health of soil, eco-system and people by relying on ecological process,
bio diversity and natural cycles and adapted to local conditions than
use of inputs with adverse effect”. - (IFOAM)
• Organic farming uses organic source of nutrients and pesticides but excludes or
strictly limits the use of synthetic fertilizers, pesticides (which include herbicides,
insecticides and fungicides)

5. Worldwide production of organic farming
More than 120 countries has been practiced organic farming.
33 million hectares of organic land with 633,891 farms.
Fig1. Global organic land by continent
Fibl, survey 2011

6.  Weeds can be considered a significant problem because they tend
to decrease crop yields. Increasing competition for space, water,
sunlight, nutrients, pests and diseases.
 The widespread use of agro-chemicals has results adversely affect
environment and cause various health problems.
 Herbicides use can cause some weed species to dominate in fields
because this weeds develop resistance to herbicides.
 Herbicides are capable of destroying weeds that are harmless to
crops, resulting in a potential decrease in weed biodiversity.
 Organic system of weed control, weeds will never be eliminated
but only managed.

7. Weed prevention
Weed eradication
Weed control
Weed management principles
 Weed prevention- prevent the entry
or establishment of weeds in an area.
 Weed eradication – complete
removal or elimination of weeds
after it has established in an area.
 Weed control- process of limiting
infestation of the weed plant so that
crops can be grown profitably.

8. Cattle 25%
Hogs 25%
Horses 10-12%
Sheep 10-12%
Chickens 2%
Table 1: Weed seeds remaining viable after digestion
Taylor and Renner, 2010
•Very few weed seeds survive in pelletized feed products
•Weedy feed = potentially weedy manure

9. Ensiling for 8 weeks
Table 2: Average percentage of viable seed remaining after fermentation
in a silo, rumen digestion and both
Blackshaw and Rode (1991)

10. Table 3: Weed seed germination as influenced by different organic manures
(Laboratory study)
Treatment
Cyperus rotundus Echinochloa colonum Trianthema portulacastrum Phyllanthus niruri
Per kg
soil
Millions
/ha soil
%
increase
Per kg
soil
Millions/
ha soil
%
increase
Per kg
soil
Millions/
ha soil
%
increase
Per kg
soil
Millions/
ha soil
%
increase
Untreated
control
2.68 5.36 - 0.70 1.40 - 0.14 0.28 - 0.07 0.14 -
FYM 3.30 6.60 23.1 0.80 1.60 14.28 0.18 0.36 28.57 0.10 0.20 42.86
Goat
manure
2.54 5.08 -5.22 0.68 1.36 -2.86 0.13 0.26 -7.14 0.06 0.12 -14.29
Pressmud 1.81 3.62 -32.50 0.51 1.02 -27.14 0.06 0.12 -57.14 - - -
Neem
cake
1.89 3.78 -29.50 0.54 1.08 -22.86 0.07 0.14 -50.00 - - -
Pungam 2.47 4.94 -7.84 0.65 1.30 -7.14 0.14 0.28 0.00 0.06 0.12 -14.30
Glyricidia 2.42 4.84 -9.70 0.69 1.38 -1.43 0.13 0.26 -7.14 0.06 0.12 -14.30
LSD
(P=0.05)
0.21 0.42 - 0.09 0.18 - 0.03 0.06 - 0.02 0.04 -
Geetha and Kathiresan, 2006Annamalainagar (TN)

11. Physical
method
Tillage, hand weeding , hand pulling , inter cultivation( hoeing)
digging , sickling , mowing , cutting , chaining , dredging , burning
and flaming .
Cultural
method
Crop rotation, Cover crops, Inter cropping, Planting pattern,
Variety selection, Water management, stale seed bed techniques,
seed rate , trap crops etc.
Biological
Classical approach- using insects, fish ,competitive plants;
Bio herbicide approach - using microbial plant pathogens( fungi-
myco-herbicides):
Naturally occurring herbicides- secondary plant products
IWM
Physical + Cultural + Biological method
Components in organic weed management

12. Physical /mechanical method of weed management practices
12

13. Physical /Mechanical weed control
 Physical force either manual , animal or mechanical power is used to pull out or kill the weeds.
 It is both time consuming and labour-intensive but is the most effective method for managing
weeds.
Physical weed control aims at directly suppressing/removing weed plants in the field to enhance
the competitiveness of the crop.
Implements Weed control effect
Plough Disrupts growth and seed produce. Buries perennial seeds
produced and their below ground root/stem systems
Cultivators /disc
cultivators
Disrupts growth and seed produce, fragments perennial
weeds and underground root/stem systems
Harrow destroy / kills small weed plants
Roller improves the germination condition for the crop
Weed harrow covers small weeds plants with soil and /or uproots them
Inter row
cultivator
cover small weed plants with soil, uproots them or cuts
them off
Brush weeder covers small weed plants with soil or uproots them
Weed mower cuts of weeds in growing crops

14. Table 4. Effect of different non chemical weed control treatments on total weed dry weight,
WCE, seed yield and weed index in organically grown sunflower
Treatments
Total weed dry weight
(kg/ha) 45 DAS
WCE (%)
45 DAS
Seed yield
(kg/ha)
Weed index
T1- Hand weeding at 25 & 45 DAS 2.73 (539.3) 81.23 1250 5.8
T2- Manually operated weeder at 25 & 45
DAS
3.03 (1058.7) 62.00 1140 14.1
T3- - Manually operated weeder at 25 DAS +
Hand weeding at 45 DAS
2.98 (943.3) 69.50 1230 7.3
T4- In situ green manuring- cowpea
incorporation at 45 DAS
3.10 (1253.3) 56.39 1083 18.4
T5- In situ green manuring- sunhemp
incorporation at 45 DAS
3.09 (1233.3) 57.09 1024 22.8
T6- Intercropping with coriander 3.16 (1440.0) 49.90 990 25.4
T7- Mulching with crop residues- maize
stalks at 5 t/ha
3.15 (1401.3) 51.24 1085 18.2
T8- Mulching with weeds at 5 t/ha 3.18 (1512.0) 47.39 1036 21.9
T9- Stale seed bed 3.29 (1937.3) 32.59 1006 24.2
T10- Spray of eucalyptus oil at 0.4% at 3 DAS 3.37 (2330.0) 18.93 995 25.0
T11- Weed free 0.30 (0.0) 100.0 1327 -
T12- Weedy check 3.46 (2874.0) 845 36.3
CD (P=0.05) 0.135 67.8 -
Satyareddy, 2007TNAU, Coimbatore

15. Table 5. Distribution of weed seeds (total no./200 g dry soil) in the organic soil profile after
cultivation treatments. Figures in brackets are percentages of total seed numbers
Depth (cm)
Cultivation method
Power harrow Rotary hoe Plough Undisturbed
0-5 157 (50) 133 (52) 57 (27) 113 (53)
5-10 91 (29) 75 (30) 78 (37) 53 (25)
10-15 55 (17) 41 (16) 50 (24) 39 (18)
15-20 13 (4) 5 (2) 24 (11) 8 (4)
Rahman et al. (2000)Hamilton (New Zealand)

16. Treatments
WCE (%)
Grain yield
(kg/ha)
Seed yield (kg/ha)
Maize Sunflower Maize Sunflower
Stale seedbed technique 30.7 31.5 4029 966
insitu green manure cowpea incorporation at 45 DAS 70.7 58.4 4177 1002
Crop residue mulch at 5 t ha-1 71.9 64.5 5174 1226
Twin wheel hoe weeding twice at 20 and 40 DAS 92.3 93.7 5794 1395
Hand weeding twice at 20 and 40 DAS (T5) 90.7 90.8 5365 1309
Stale seedbed technique + insitu
green manure cowpea incorporation at 45 DAS
75.6 67.9 4266 1029
Stale seedbed technique + crop residue mulch at 5 t/ha 77.0 72.4 5281 1276
Stale seedbed technique + twin wheel hoe weeding at 40 DAS 87.8 86.2 4691 1122
Stale seedbed technique + hand weeding at 40 DAS 91.5 90.5 4747 1137
Twin wheel hoe weeding at 20 DAS + hand weeding at 40 DAS 93.5 94.7 5831 1410
Unweeded control 3604 875
CD (P=0.05) 424 85
16
Table 6. Effect of weed management methods on weed control efficiency, grain and seed yield of organically
grown maize – sunflower cropping system
Bhuvaneswari et al., 2010TNAU, Coimbatore

17. Table 7. Effect of various weed control treatments on weed density, weed dry
weight , and yield of cotton
Treatment At final picking No of
bolls
/plant
Boll
weight
(g)
Kapas
yield
(t/ha)
Weed density
(no/m2)
Weed dry
weight(g/m2)
Un weeded check 7.9 25.3 9.6 4.42 0.92
HW( 20, 40 &60 DAS) 4.8 15.9 36.9 5.26 2.32
Inter cultivation ( 20 ,40
&60DAS)
5.9 19.9 15.2 4.80 1.49
Mechanical weeding with
power weeder (20, 40 &
60 DAS)
5.2 17.5 18.4 4.99 1.59
LSD (P=0.05) 0.9 3.9 3.9 NS 0.26
Guntur ( A.P) Rao,2013

18. Fig 2. Some implements for mechanical weed management

19. Rotation of
dense crops (oats, rye)
with open crops (row c
rops
Field pea-oat-
mustard cover crop
Red Clover – cover
crop
Intercropping in sunflower Sorghum-smother crop
Agronomic management
practices
Living mulch
19

20. Cultural / Agronomic management practices
 Crop rotation:
Crop rotation involves alternating different crop a systematic sequence on the same land.
Important strategy for developing a sound long term weed control.
 Cover crops:
May reduce weed emergence by 75-90%.
Ex: Sudan grass, buckwheat, annual rye grass, sesbania
 Intercropping :
growing a smother crop between rows of the main crop
 Planting pattern:
Crop population, spatial arrangement, and the choice of cultivar (variety) .
 Mulching: Allelopathic chemicals in the mulch also can physically suppress seedling
emergence.
a. Living mulch - plant species that grows densely and low to the ground .
b. Organic mulch – Such materials as straw, bark, and composted material

21. Cultural / Agronomic management practices
 SOIL SOLARIZATION
o The basic principle of soil solarization is to elevate the temperature in a moist soil to
a lethal level that directly affects the viability of certain organisms.
o Currently, the most common practice of soil solarization is based on mulching
moistened soil with transparent PE.
o Soil moisture improves temperature conductivity in soil and the sensitivity of
microorganisms to toxic agents. Hence, pest control is better under "wet heating"
than "dry heating". This applies also to weed control, presumably because moist
seeds are in a more advanced metabolic activity
 COMPETITIVE CROP CULTIVARS
 Crop cultivars vary in their abilities to compete with and adapt to weeds. Several
characteristics can enhance a cultivar’s ability to compete with weeds, including its
physical structure.
 Tall grain crops, for example, are generally more competitive with weeds because
they intercept light.
 A large leaf area and high biomass production can also contribute to a cultivar’s
competitive abilities.

22. Figure 3. Weed-suppressive effects of maize–legume intercropping in organic farming,
(a) in Athens and (b) in Mavrica
Bilalis et al., 2010Athens (Greece)

23. Table 8. Rotation with trap crops in tobacco
Rotation Orabanche dry
weight (kg/ha)
Tobacco yield (kg/ha)
Tobacco- tobacco 239.2 1002
Chilli-tobacco 175.1 1384
Peanut – rabi sorghum +
tabacco
122.8 1320
Peanut –chickpea-
tobacco
108.8 1395
Pea nut+ pigeon pea-
tobacco
82.1 1555
Maize -chickpea-tobbacco 110.7 1494
CD at 5% 33.8 168
Anon ., 1993Anathapur (A.P)

24. Table 9. Dry matter of grasses, sedges and broad-leaved weeds and weed dry matter
accumulation at 25 DAT in rice under different crop sequence
Crop sequence Grasses
(g/m2)
Sedges
(g/m2)
BLW
(g/m2)
WDMP
(g/m2)
Rice-wheat 8.80 6.43 8.10 4.37
Rice-chickpea 5.13 4.17 3.03 4.08
Rice-wheat-green gram 2.18 1.97 1.14 3.09
Rice-wheat- Sesbania (GM) 2.93 3.36 2.01 3.77
Rice-mustard-green gram 3.04 2.44 2.00 3.72
Rice-pea 5.42 4.29 3.36 4.26
Rice-lentil-Mustard (3:1)-cowpea 3.12 2.79 1.76 3.60
Rice-Maize + pea (1:1) - cowpea 3.71 2.78 2.56 3.84
Rice-potato-green gram 2.38 2.48 1.40 3.52
LSD(p=0.05) 2.87 0.69 1.53 0.71
Singh et al., 2008Punjab

25. Table 10. Effects of maize planting density and cowpea living mulch on
weed above ground biomass (g/m2) per species and total at harvest time
Density
(plants/m2)]
Biomass (g/m2)
Maize Cowpea
Setaria
viridis
Echinochloa
crus-galli
Chenopodium
album
Amaranthus
blitoides
Total
7.5
0 74.9 239.1 97.6 88.7 500.3
15 42.4 156.2 84.1 59.8 342.5
30 39.8 88.6 60.2 53.0 241.6
9
0 54.4 201.8 75.2 51.9 383.3
15 37.8 110.6 93.9 62.7 305.0
30 31.5 70.1 41.6 52.1 195.3
LSD (P=0.05) 21.0 43.9 32.9 34.8 64.7
Jamshidi et al., 2013New zealand

26. Fig. 4. Effect of maize crop and cowpea density on organic maize grain yield
Jamshidi et al., 2013Newzealand

27. Fig 5. Weed population change during 3 years with autumn and winter fallow (no cover
crops-light grey), autumn fallow (cover crop in winter- dark grey), and without fallow (cover
crop in autumn and winter-black) in organic system
Skora Neto and campos, 2004

28. Fig 6. Effects of cover crop mulch thickness on weed suppression
Altieri et al., 2011

29. Treatment WCE (%)
Cane yield
(t/ha)
Sugar yield
(t/ha)
B:C
Raw pressmud as mulch @25 t/ha 62.5 119.0 13.05 2.64
C0 5 cowpea intercrop (2 lines) 63.8 112.8 11.24 2.61
Trash mulching @5 t/ha 71.8 128.5 15.28 2.90
Hand weeding on 30 and 55 DAP 67.8 118.4 12.34 2.63
Farmer practice (3 hoengs) 66.9 115.7 11.75 2.61
Unweeded control - 82.4 8.36 -
CD (P=0.05) - 8.59 1.26 -
Table 11. Effect of organic mulches on WCE, yield and economics of
sugarcane (Pooled data of two plant crop 1999-2000 and 2000-2001
Jayachandran et al., 2004Cuddalore (TN)

30. Table 12. Weed seed bank in soil after solarization and other agronomical
practices (no./100 g soil)
Gwalior, MP Arora and Tomer, 2012
Weeds
Solarized Non-solarized Stale seed bed Deep ploughing
2004 2005 2004 2005 2004 2005 2004 2005
Grasses
Echinochloa crusgalli 0.06 0.00 3.19 3.56 2.17 2.46 2.08 1.97
Broad leaved weeds
Digera arvensis 0.00 0.00 0.08 0.10 0.25 0.35 0.17 0.25
Commelina
benghalensis
0.00 0.00 0.06 0.18 0.00 0.00 0.00 0.01
Trianthema monogyna 0.08 0.00 0.12 0.23 0.08 0.17 0.00 0.02
Chenopodium album 0.00 0.00 0.25 0.32 0.06 0.08 0.00 0.00
Phyllanthus niruri 0.00 0.00 0.00 0.00 0.08 0.04 0.00 0.00
Sedges
Cyperus rotundus 0.06 0.12 0.19 0.20 0.25 0.14 0.12 0.67
Total 0.20 0.12 3.89 4.59 2.89 3.24 2.37 2.92

31. Effect of soil solarization and farmyard manure application on weed control and
productivity of organic sunflower
T1 - Irrigation up to FC+10 t FYM/ha before solarization with TPE 0.05 mm for 60 days;
T2 -Irrigation up to FC + 10 t FYM/ha before solarization with TPE 0.05 mm for 45 days;
T3 -Irrigation up to FC + 10 t FYM/ha after solarization with TPE 0.05 mm for 60 days;
T4- Irrigation up to FC + 10 t FYM/ha after solarization with TPE 0.05 mm for 45 days;
T5- Irrigation up to 50% FC + 10 t FYM/ha before solarization with TPE 0.05 mm for 60 days;
T6- Irrigation up to 50% FC + 10 t FYM/ha before solarization with TPE 0.05 mm for 45 days;
T7- Irrigation up to 50% FC + 10 t FYM/ha after solarization with TPE 0.05 mm for 60 days;
T8- Irrigation up to 50% FC + 10 t FYM/ha after solarization with TPE 0.05 mm for 45 days;
T9- Control (dry) + 10 t FYM/ha before solarization with TPE 0.05 mm for 60 days;
T10- Control (dry) + 10 t FYM/ha before solarization with TPE 0.05 mm for 45 days;
T11- Control (dry) + 10 t FYM/ha after solarization with TPE 0.05 mm for 60 days;
T12- Control (dry) + 10 t FYM/ha after solarization with TPE 0.05 mm for 45 days;
T13- Non-solarized control + 10 t FYM/ha (weedy check);
T14- Two hand weedings + 10 t FYM/ha
Thimmegowda et al., 2007Bangalore

32. Treatments
Weed count
(No. m-2)
Weed dry weight
(g/0.25 m-2)
Seed yield
(t/ha)
T1 7.1 (50.7) 2.48 (5.65) 3.26
T2 7.4 (55.0) 2.51 (5.82) 3.25
T3 8.1 (65.0) 2.81 (7.43) 3.16
T4 8.4 (70.2) 2.83 (7.54) 3.11
T5 9.3 (86.3) 3.19 (9.70) 2.98
T6 9.6 (91.3) 3.23 (9.98) 2.94
T7 10.5 (110.0) 3.59 (12.48) 2.88
T8 10.8 (116.3) 3.65 (12.89) 2.88
T9 12.7 (160.2) 4.24 (17.53) 2.27
T10 13.0 (167.5) 4.32 (18.25) 2.25
T11 13.8 (190.2) 4.59 (20.67) 2.10
T12 13.9 (193.5) 4.64 (21.08) 2.10
T13 16.8 (283.3) 5.75 (32.80) 1.47
T14 6.2 (39.2) 2.27 (4.75) 2.47
CD (P=0.05) 0.6 0.21 0.25
Table 13: Effect of soil solarization and farmyard manure application on weed
count, weed dry weight and productivity of organic sunflower
Thimmegowda et al., 2007Bangalore

33. Days after
rice emergence
Shoot biomass Seed production
20-cm row 30-cm row 20-cm row 30-cm row
Jungle rice g plant-1 no. plant-1
0 5.2 6.6 2200 3100
15 3.5 4.8 1400 2000
30 1.6 2.6 600 1100
Barnyard grass
0 11.0 13.8 2100 2900
15 6.5 9.0 1200 1800
30 3.5 5.2 600 900
Chauhan and Johnson (2010)
Table 14. Effect of rice row spacing and weed emergence time (days after
emergence) on biomass and seed production of jungle rice and
barnyard grass
IRRI, Philippines

34. Table 15. Influence of crop establishment methods on weed density, wed
dry weight and yield of rice
Treatment Weed
density
(no./m2)
Weed dry
weight
(g/m)
Grain/panicle Grain yield
(t/ha)
SRI 8.1 6.2 92.1 4.27
Direct sown 8.8 6.7 82.5 3.89
Transplanting 7.6 5.9 94.4 4.41
LSD (P=0.05) 0.6 0.4 8.0 0.36
Hydrabad (A.P) Parameswari et al., 2012

35. Table 16: Influence of spacing and seed rate on weed cover, weed dry
weight and yield of finger millet in organic field
Treatments
Weed cover score
Weed dry matter
(g/m2)
Grain yield (kg/ha)
Spacing (cm)
10 1.0d 29.85c 3829a
15 2.0c 32.83d 3790b
20 4.5b 36.82c 2945c
25 6.0a 37.25b 2681d
30 7.0a 42.36a 2665d
Seed rate (kg/ha)
10 6.3a 44.73a 2598d
15 3.9b 39.61b 2701c
20 1.5c 30.09c 2739b
25 0.8d 24.58d 3822a
30 0.7d 17.10c 3848a
WCS=Weed cover score using scale 1-10 where 0=no weed cover and 10= complete weed cover
Shinggu et al., 2009
Nigeria

36. Table 17: Weed population at 20 DAS and weed dry weight (at harvest) of soybean in the
kharif season as affected by crop husbandry practices adopted during summer season
Treatment
Monocot weeds
(No./m2)
Dicot weeds
(No./m2)
Total weed
count (No./m2)
Total weed
dry weight
(g/m2)
Grain yield
(kg/ha)
Crop husbandry practices
Control/farmers’ practice 176 384 560 177 844
Repeated tillage without
irrigation
160 218 378 117 945
Repeated tillage with
irrigation
118 50 168 156 1100
Soil solarization 76 46 122 105 1302
Summer cowpea for fodder 240 22 262 116 1083
Wheat straw incorporation 70 794 864 86 1165
LSD (P=0.05) 59 205 184 50 130
Das and Yaduraju, 2008IARI, New Delhi

38. • Flame Cultivation: Weed control method using brief exposure to high
temperatures. Water in plant tissues rapidly expands, ruptures cells, and
disrupts cellular processes.
• Flame weeding, also called flame cultivation, relies on propane gas burners
to produce a carefully controlled and directed flame that briefly passes over
the weeds.
• Weeds are most susceptible to flaming when they are seedlings, 1 or 2
inches tall.
• Broadleaf weeds are more susceptible to lethal flaming than grasses.
• Grasses develop a protective sheath by the time they are approximately 1
inch tall and may require a second flaming.
• Repeated flaming can likewise be used to suppress perennial weeds such as
field bindweed.

39. How Propane-Fueled Flame Weeding Works
A Closer Look: Flame Weeding at the Cell Level
• Flame weeding systems control weeds by applying direct heat to
plants, which rapidly changes the internal temperature of plant cells.
• This rapid temperature change expands the cell’s contents—95
percent of which is water—causing the cell walls to rupture.
• This primary cause of cellular death is followed by the evaporation
of the water that is released when the cell walls burst, which rapidly
dries out the affected plant tissue.
• Direct heat injury also causes cell proteins to denature, which results
in cell desiccation and ultimately the loss of cell function .
• The loss of water and denaturing of proteins drastically reduces the
weed’s competitive ability to survive and kills the plant.
• During the flame weeding process, propane-fueled burners can
generate combustion temperatures as high as 1,900 degrees Celsius,
well above the temperature required for proteins to denature.

40. Before Flame Weeding 10 Days After Flame Weeding
Effect of flaming on weeds

41. • The effectiveness of flame weeding
treatment can be easily assessed in
the field by conducting a simple
fingerprint test a few minutes after
treatment. To conduct the test, after
properly shutting down the flame
weeding system, the operator can
inspect the plants by placing a
treated weed leaf between his or her
thumb and index finger. If a darkened
impression is visible after firmly
pressing on the leaf surface, as
shown in Figure, it is likely evidence
of a loss of internal pressure within
the leaf due to water leakage from
ruptured cell walls.
Assessing Flame Weeding Effectiveness: A Rapid
Field Test

42. Fig 7. Effects of propane dose on dry matter reduction of barnyard grass [E. crus-
galli (L.) Beauv.], bindweed (C. arvensis L.) as influenced by growth stage.
Datta and Stavens, 2013Nebraska, USA

43. Mechanical weeding
• Soil type can limit effectiveness
• Operation takes less time
• Can be performed in more crops
• Disturbs soil structure
• Soil must be dry
• Effects may be longer lasting
• Cheaper
• Timing of operation is critical
• Stimulates further weed
germination
• Windiness increases effectiveness
Flame weeding
• Soil type does not matter
• Operation takes more time
• Few crops can withstand flaming
• Preserves soil structure
• Soil can be wet or dry
• Little residual effect
• More expensive
• Timing of operation is critical
• Does not stimulate weed
germination
• Windiness decreases
effectiveness
Comparison between mechanical and flame weeding

44. Weed management in organic
AgricultureBiological method of weed management
44

45. Biological method
Use of living organism’s viz., insects, disease causing organisms, herbivorous
fish, snails or even competitive plants for the control of weeds is called biological
control.
 Classical approach – using insects, competitive plants , aquatic fish etc
 Bioherbicides approach – using microbial plant pathogens
 Naturally occurring herbicides – using secondary plant products and microbial
toxins as naturally pesticides (allelo chemicals)
Qualities of bio-agent
• It must feed or affect only one host and not other useful plants
• It must be free of predators or parasites.
• It must readily adapt to environment conditions.
• It must be able to kill the weed or at least prevent its reproduction in some direct or
indirect way.

46. Classical biological control program
Mode of action
a. Differential growth habits, competitive ability of crops and varieties E.g. Groundnut,
cowpea.
b. Insects kill the plants by defoliation, boring and weakening structure of the plant.
c. Pathogenic organisms damage the host plants through, production of toxins, and
malfunctioning of physiological processes.
Merits
Least harm to the environment
No residual effect
Relatively cheaper and comparatively long lasting effect
Will not affect non-targeted plants and safer in usage

47. Trade name Pathogen Target weed
Devine Phyophthora palmivora
Morreria odorata (Strangler vine)
in citrus
Collego
Colletotrichum
gleosporoides f.sp.
Aeschynomene
Aeschynomene virginica (Northen
joint vetch) in rice and soybean
Biopolaris Biopolaris sorghicola Sorghum halepense (Johnson grass)
Biolophos Streptomyces hygroscopius General vegetation(non-specific)
LUBAO 11
Colletotrichum
gleosporoides f.sp.Cuscuttae
Cuscutta sp. (Dodder)
ABG 5003 Cercospora rodmanii
Eichhornea crassipes
(water hyancinth)
Commercial mycoherbicides
Mycoherbicides: microbial plant pathogen to suppress or kill the weeds

48. Table 18: Post-dispersal predation of weed seeds in rice fields
Weed species
% of weed seeds removed
Invertebrate Vertebrate
Digitaria ciliaris 98.5 40.9
Echinochloa colona 85.7 37.0
Eleusine indica 96.6 36.3
Chauhan et al., 2010IRRI, Philippines

49. Table 19: Effect of soil microorganisms on Parthenium seed germination
and seedling emergence
Treatment Seed germination (%) Seedling emergence (%)
Corynespora cassicola 21.0 (27.27) 19.2 (26.02)
Curvularia lunata 21.7 (27.8) 21.7 (27.8)
Curvularia sp. 35.2 (36.42) 14.5 (22.37)
Fusarium oxysporum 0.0 (2.87) 0.0 (9.10)
F. moniliforme 0.0 (2.87) 0.0 (9.10)
Monilla sp. 43.0 (40.98) 41.2 (39.96)
Trichoderma harzianum 0.0 (2.87) 0.0 (9.10)
Control 78.7 (62.55) 78.2 (62.2)
TNAU Jeyalakshmi et al. (2004)

50. Fig 8. Effect of emulsified water formulations of sesame root exudates (mg/g) on the germination of
(A)Chenopodium album , (B)Anagaleis arvensis , (C)Melilotus alba, (D)Spergula arvensis,
Lalit Kumar and Varshney, 2008IIPR, Kanpur

51. • C. rotundus growth in sesame and rose
pots. Since the root exudates of rose were
found beneficial to the weed therefore 10
days old weed plants in rose pots are very
vigor. But the height of one month old
weed in sesame pot is very meager that
confirm the antagonist effect of sesame
root exudates on C. rotundus.
• Effect of root exuded lipophilic chemical
fraction of sesame on C. Rotundas
vegetative growth. Root exudates were
collected by growing the sesame plants in
root exudate trapping system. Collected
exudates were fractionated and lipophilic
fraction was removed. In treatments the
soil of pots was treated with 90 &75 μg
ml-1 concentrations of the isolated
fraction.
IIPR, Kanpur Lalit kumar et al., 2013
Fig 9. Effect of sesame plant and root exudates on Cyperus rotundus

52. Table 20. Effect of plant water extracts on dry matter of wild oat, canary
grass and yield components of organic wheat production
Treatment Dose
(ha-1)
Dry
weight
wild oat
(g m-2)
Dry weight
Canary
grass
(g m-2)
no of
grain spike
-1
Grain
yield
(Mg ha-1)
Sorghum 12 L 48.59 64.04 50.1 3.7 (32)
Sorghum + eucalyptus 6 L each 44.51 63.87 50.2 4.4 (57)
Sorghum + sunflower 6 L each 37.93 58.59 52.0 4.4 (57)
Sorghum + sesame 6 L each 46.88 66.22 50.8 4.5 (61)
Sorghum + tobacco 6 L each 53.08 71.31 49.6 3.5 (25)
Sorghum + brassica 6 L each 46.72 65.69 51.6 3.6 (29)
Sorghum + sunflower 12 L each 35.73 53.86 52.2 4.5 (61)
Weedy check - 61.74 83.29 49.8 2.8
Faisalabad (Pakistan) Muhammad et al ., 2009

53. Use of Organic herbicides
 Corn gluten meal (pre-emergent herbicide)
Suppresses many common grasses and herbaceous weeds
WeedBan™ and Corn Weed Blocker™
• Corn gluten meal (CGM) is a waste product left over from the processing of corn to
produce corn syrup. Corn gluten meal is 60% protein and approximately 10% nitrogen
(N) by weight. It has been used as an ingredient in dog food, fish food, and other
animal feeds
 Commonly based on vinegar or lemon juice or clove oil ingredients (post-emergent
burndown herbicide)
Perennials may require multiple applications
Burnout™, Bioganic™, AllDown ™, MATRAN™, and Weed Bye Bye™
• Vinegar is obtained by the aerobic bacterial oxidation of ethanol, producing acetic acid.
The characteristic odor of vinegar is due to acetic acid, and effectiveness of vinegar as
a weed killer increases with its concentration. For instance, 200 grain vinegar contains
20% acetic acid. This product is much stronger than table vinegar, which contains
about 5% acetic acid (Evans et al. 2009).
 GreenMatch® and GreenMatch EX®
• The active ingredient of GreenMatch is 55% d-limonene, which is a major component
of orange oil. It is post emergent, non selective, contact herbicide.
• The d-limonene dissolves the waxy cuticle of plants, causing them to desiccate and die.
GreenMatch is more effective for broadleaf weeds than grassy weeds.

54. Table 21: The ingredients of some natural-products herbicides available on the
market.
Active ingredients Product name Concentration (L/ha) Company
Acetic acid (5%) Vinegar Undiluted (188) Heinz North America
Acetic acid (10%) Acetic acid 30% (18.7)
Ricca Chemical
Company, Arlington
Citric acid (10%) Citric acid Undiluted (188)
Ricca Chemical
Company, Arlington
Citric acid (5%) +
garlic (0.25%)
Alldown Undiluted (188)
Summerset Products,
Inc. Bloomington MN;
www.sumerset.com
Citric acid (10%)
+ garlic (0.2%)
Groundforce 10% (18.8)
Abby Labs, Inc. Ramsey
MN;
www.abbylabs.com
Clove oil (45.6%) Matran II 20% (37.5)
EcoSMART Tech.,
Franklin, TN;
www.ecosmart.com
Corn gluten meal
(CGM)
CGM 4 t
Bioweed, Environmental
FactorOshawa, ON,
Canada;
www.environmental
factor.com
Abouziena et al., 2009

55. Table 22: Effects of foliar applied PORGANIC on chlorophyll a, b of barnyard
grass young leaf at 1, 3, 5 and 7 days after treatment (DAT).
PORGANIC
rate
(kg a.i. ha-1)
Chlorophyll a (μg/cm2) Chlorophyll b (μg/cm2)
1 DAT 3 DAT 5 DAT 7 DAT 1DAT 3 DAT 5 DAT 7 DAT
0 27.37 28.18 28.93 29.16 12.20 13.04 13.94 14.13
2.5 25.39 24.16 18.29 15.34 10.54 9.94 7.61 5.29
5 23.00 19.79 17.65 13.03 9.34 8.20 6.69 4.97
10 16.12 14.77 13.27 9.45 7.44 6.51 5.90 3.64
20 14.35 12.36 11.27 7.15 6.76 5.75 4.11 2.97
Montinee et al., 2013Bangkok, Thailand

56. Fig 10. Conductivity values (μS/cm) in leaf discs of barnyardgrass after
treatment with PORGANIC for 1, 3, 5 and 7 days.
Montinee et al., 2013Bangkok, Thailand

57. Integrated weed management
Combination of two or more weed-control methods at low
input levels to reduce weed competition in a given cropping
system below the economical threshold level.
Advantages of IWM
It shifts the crop-weed competition in favour of crop
Prevents weed shift towards perennial nature
No environmental pollution
Gives higher net return
Suitable for high cropping intensity

58. Table 23. Effect of weed control measures on population, biomass of weeds an organic green
pod yield in garden pea.
Treatments
Weed population m-2
Weed biomass
(g m-2)
WCE
(%)
Green pod yield
(Mg ha-1)
2004 2005 2004 2005 2004 2005
Hand weeding 30 DAS 12.5 (155) 14.0 (196) 15.9 (252) 17.8 (314) 53 5.9 3.2
Hand weeding 30 and 60
DAS
9.2 (85) 9.7 (96) 8.3 (69) 11.4 (128) 84 10.9 6.2
Hoeing (30 DAS) 14.3 (203) 16.7 (280) 19.4 (375) 21.9 (478 30 4.5 2.3
Mulching (up to 30 DAS) 11.8 (140) 13.0 (168) 15.4 (237) 16.7 (277) 58 7.4 3.6
Hand weeding
(30 DAS) +mulching
10.7 (115) 12.2 (148) 12.8 (165) 14.4 (206) 69 8.8 4.4
Stale seedbed 11.4 (131) 13.7 (187) 16.5 (271) 17.2 (294) 53 8.3 3.8
Stale seedbed + hand
weeding (60 DAS)
9.9 (99) 10.9 (120) 10.8 (116) 12.9 (164) 77 10.2 6.4
Unweeded control 15.8 (249) 21.8 (477) 21.8 (475) 27.2 (735) - 2.8 0.5
LSD (p =0.05) 1.3 2.1 1.5 2.1 - 1.0 0.8
Gopinath et al., 2008Almora

59. Table 24. Total weed density and weed dry weight at 60 DAP in finger
millet as influenced by weed management practices .
Treatment Weed density
(no./m2)
Weed dry weight
(g/m2)
T1-Passing wheel hoe at 20, 30 and 40 DAP 1.62 (50.2) 1.62 (39.7)
T2- Inter cultivation twice at 20 and 35 DAP 1.92 (80.9) 1.76 (55.8)
T3 Stale seedbed technique 2.25 (177.5) 1.91 (80.0)
T4 -T1 + one hand weeding 1.64 (41.2) 1.10 (10.7)
T5- T2 + one hand weeding 1.69 (47.3) 1.65 (42.9)
T6- T3 + Inter cultivation twice at 20 and 35 DAP 1.50 (29.6) 1.00 (8.0)
T7-Organic mulching 10 t/ha after transplanting 2.10 (124.0) 1.74 (52.4)
T8- Growing cover crops (Horse gram/cowpea) and passing blade
hoe
1.89 (76.0) 1.74 (53.5)
T9 - Directed spray of Eucalyptus leaf extract on weeds 2.22 (165.5) 1.92 (81.3)
T10 -Directed spray of cattle urine on weeds 2.27 (185.8) 1.84 (67.7)
T11 – Hand weeding twice at 20 and 30 DAP 1.45 (26.3) 0.92 (6.4)
T12- Unweeded check 2.45 (279.6) 1.99 (95.1)
LSD(P=0.05) 0.20 0.06
UAS, Bangalore Patil et al., 2013

60. Table 25. Weed control efficiency (%) at 60 DAP and yield of organic finger millet
as influenced by weed management practices .
Treatment WCE
(%)
Grain yield
(t/ha)
Straw yield
(t/ha)
T1-Passing wheel hoe at 20, 30 and 40 DAP 58.2 4.09 6.56
T2- Inter cultivation twice at 20 and 35 DAP 41.3 3.93 6.30
T3 Stale seedbed technique 15.8 3.39 4.90
T4 -T1 + one hand weeding 88.7 5.14 7.10
T5- T2 + one hand weeding 54.9 4.22 6.20
T6- T3 + Inter cultivation twice at 20 and 35 DAP 91.6 5.36 7.53
T7-Organic mulching 10 t/ha after transplanting 45.2 3.77 6.30
T8- Growing cover crops (Horse gram/cowpea) and passing
blade hoe
43.7 3.20 6.20
T9 - Directed spray of Eucalyptus leaf extract on weeds 14.5 2.92 5.26
T10 -Directed spray of cattle urine on weeds 28.8 3.30 5.60
T11 – Hand weeding twice at 20 and 30 DAP 93.2 5.46 7.20
T9- Unweeded check 0.0 2.73 4.50
LSD(P=0.05) - 0.95 0.63
UAS, Bangalore Patil et al., 2013

61. Table 26. Effects of stale seedbed technique and hand weeding on weed
density and weed dry weight 60 DAS and on grain yield of rice
Treatment
Grasses Broad leaves Sedges Weed dry matter
(g/m2)
Grain yield
(Kg/ha)No./m2
No stale seedbed 78 52 44 205 386
Stale seedbed (harrow) with
one irrigation
34 22 14 83 1442
Stale seedbed with (harrow)
two irrigation
18 8 8 29 2256
No stale seedbed + HW 24 12 26 52 1628
Stale seedbed with one
irrigation + HW
12 8 5 31 2144
Stale seedbed with two
irrigation + HW
4 2 3 7 2621
CD at 5% 12 5 8 21 240
Karnal (Haryana) Virender Kumar et al., 2013

62. Economics of weed management

63. Treatments
Grain
yield
(t ha-1)
Cost of
weeding
(Rs. ha-1)
Total cost
of
cultivation
Gross
income
(Rs. ha-1)
Net
income
(Rs. ha-1)
Hand weeding (20 and 30
DAS)
5.05 3484 11702 30629.70 18927.30
Single roller weeder(20
and 30 DAS)
4.46 976 9194 2708.90 17.893.90
Power weeder(20 and 30
DAS)
4.73 822 9040 27631.10 19591.10
Unweeded check 1.41 - 8218 8652.30 434.30
CD at 5 % 0.35 - - - -
Table 27. Effect of weed control treatments on economics in direct seeded
rice
Chhattisgarh Viren et al. (2005)

64. Table 28. Effect of various weed control treatments on yield and economics of
maize organic production system
Treatment Weed control
efficiency (%)
Maize grain
equivalent Yield
(t/ha)
B:C
ratio
Soybean intercropping (no weeding) 54.7 2.80 1.5
Soybean intercropping + 1MW (20
DAS)
72.4 3.84 2.4
Soybean intercropping + 1 HW (20
DAS)
69.2 3.71 1.7
2 MW 20 and 40 DAS + soybean
intercropping
73.0 3.82 2.1
Un weeded check - 2.15 -
LSD (P=0.05) - 0.24 -
Palampur (Himachal Pradesh) Saini et al., 2013

65. Table 29. Effect of weed management practices on yield and economics of
wheat (pooled year of two years)
Treatments Grain yield
(kg/ha)
Straw yield
(kg/ha)
Net return
(Rs/ha)
Benefit : cost
ratio
Mechanical weeding at 15
and 30 DAS
3826 5318 24295 1.36
Rice straw mulch ( 2t/ha) 3499 4882 21945 1.42
Neem oil spray (3%) at 30
DAS
3120 5488 29922 1.82
Weedy check 2911 4726 19892 1.32
LSD(P=0.05) 281.3 347.0 - -
Varanasi (U.P) Sharma and Singh., 2010

66. Table 30. Economics of non chemical weed control treatments in organically
grown sunflower
Treatments
Gross return
(Rs)
Cost of cultivation
(Rs)
Net return
(Rs)
B:C
T1- Hand weeding at 25 & 45 DAS 22812 12260 10552 1.86
T2- Manually operated weeder at 25 & 45
DAS
20808 10420 10388 2.00
T3- - Manually operated weeder at 25 DAS +
Hand weeding at 45 DAS
22421 10900 11521 2.06
T4- In situ green manuring- cowpea
incorporation at 45 DAS
19740 10130 9610 1.95
T5- In situ green manuring- sunhemp
incorporation at 45 DAS
18666 10130 8536 1.84
T6- Intercropping with coriander 28615 11860 16755 2.41
T7- Mulching with crop residues- maize
stalks at 5 t/ha
19802 10470 9332 1.89
T8- Mulching with weeds at 5 t/ha 18870 9700 9170 1.95
T9- Stale seed bed 18333 11380 6953 1.61
T10- Spray of eucalyptus oil at 0.4% at 3
DAS
17996 9660 8336 1.86
T11- Weed free 24251 15140 9111 1.60
T12- Weedy check 15388 8740 6648 1.76
Satyareddy, 2007TNAU, Coimbatore

67. Table 31. Economics of finger millet as influence of different weed
management practices .
Treatment Grain
yield
(t/ha)
Gross
return (Rs.
ha-1)
Net return
(Rs. ha-1) B:C
T1-Passing wheel hoe at 20, 30 and 40 DAP 4.09 71275.5 35520 1.99
T2- Inter cultivation twice at 20 and 35 DAP 3.93 68505 34790 2.03
T3 Stale seedbed technique 3.39 58305 25550 1.78
T4 -T1 + one hand weeding 5.14 87795 50840 2.38
T5- T2 + one hand weeding 4.22 72630 36275 2.00
T6- T3 + Inter cultivation twice at 20 and 35 DAP 5.36 91775 56319 2.59
T7-Organic mulching 10 t/ha after transplanting 3.77 66120 32465 1.96
T8- Growing cover crops (Horse gram/cowpea) and passing
blade hoe
3.20 57390 25050 1.77
T9 - Directed spray of Eucalyptus leaf extract on weeds 2.92 51715 19920 1.63
T10 -Directed spray of cattle urine on weeds 3.30 57930 26255 1.83
T11 – Hand weeding twice at 20 and 30 DAP 5.46 92700 56645 2.57
T12- Unweeded check 2.73 47700 16443 1.53
UAS, Bangalore Patil et al., 2013

68. CONCLUSION
Twin wheel hoe weeding at 20 DAS + hand weeding at 40 DAS can effectively
control the weeds in organic sunflower
Sorghum + sunflower plant extracts 12 L ha-1 each are a better alternative to
synthetic herbicides for wild oat and canary grass control in organic wheat
production.
Stale seedbed technique combined with inter cultivation twice at 20 and 35
DAP or passing wheel hoe at 20,30 and 40 DAP with one hand weeding would
be viable alternative for weed management inorganic finger millet production .
Flaming has a potential to be used effectively in organic crop production
systems
Physical, cultural, biologically and integrated weed management are
economically suitable methods for weed control
More research is needed to develop integrated weed management practices in
organic crop production

69. 69