Green manuring

Green manuring is the plowing under or soil incorporation of any green manure crops while they are green or soon after they flower. Green manures are forage or leguminous crops that are grown for their leafy materials needed for soil conservation.

Advantages of green manuring

1.     Improves the soil fertility

2.     Add nutrients and organic matters

3.     Improves the soil structure

4.     Improves soil aeration

5.     Helps control insect/mite pests, nematodes, and diseases

6.     Helps control weeds

7.     Promotes habitat for natural enemies

8.     Increases soil's biodiversity by stimulating the growth of beneficial microbes and other soil organisms

Green manure crops

Green manure crops

Seeding rate 
(kg/ha)

Green biomass
(t/ha) 

Dry biomass 
(t/ha) 

Nitrogen content 
(%) 

Nitrogen
(kg/ha) 

When to 
incorporate 
in the soil? (DAP) 

Azolla

50-90

8-10

1.8-3

52

35

Cowpea

40

9-10

3-4

1.4-1.5

140-150

40-60

Lablab 

7-18

5-7

 

220

45-60

Mustard

5-12

3.5

21-37

Pigeon pea

45-67

9-10

5-7

45-60

Sesbania 

20-90

1.5-4

4.3

250-360

45-50

Soybean

30-56

5-7.4

310

45-60

Sun hemp

35-40

5-19

5.5-6

1.7

108

50-60

Sweet clover 

30-40

12

6

2

 

40-50

Criteria for the selection of green manure crops

1.      Fast growing

2.      Produce abundant and succulent tops

3.      Well adapted to the local condition

4.      Can fix nitrogen in the soil

Reminders

1.     Broadcast or sow the seeds after harvest

2.     Cut the greens after flowering and plow them under

3.     Sow or transplant the next crops 1-2 weeks after the incorporation of the green manure