Backgrounder
A green manure crop is a crop grown especially to provide nitrogen for the rice crop, and to add organic matter to the soil. It is planted before or after rice when the land is vacant. Then it is ploughed into the soil as fertilizer for the rice.
It is important to choose the right green manure crop for your land. Once you have chosen it, you should be able to grow it with the least possible labour and cost. Here are some points to remember when you grow green manure.
Use zero tillage. That is, do not plough or till the field before planting the green manure. This saves time and labour. However, if your soil lacks phosphorus, you may have to add some before planting. Legumes do not need added nitrogen.
When the field is ready, just broadcast the seed. Use enough seed for a dense, close planting. This will help the green manure build up nitrogen quickly. If the field is thinly planted, the crop will have to grow for a longer period to add enough nitrogen to help the next crop.
Ordinarily, the green manure should need no extra irrigation but be able to grow on moisture already in the soil. But if the soil is very dry, irrigate once after sowing to help the seed sprout well.
Do not use any pesticides on the green manure crop as this adds to its cost. Choose the crop carefully, picking one that is not attacked by insects and diseases in your area. If you do find a problem, perhaps you could try a different species in the next season.
Acknowledgements
Written by Vrinda Kumble, Consultant Editor, ecs editorial consultant services, Pune, India
Information sources
A primer on organic-based rice farming (1991, 201 pages), by R.K. Pandey, published by the International Rice Research Institute, Box 933, Manila 1099, Philippines, and the International Institute of Tropical Agriculture, Uyo Road, PMB 5320, Ibadan, Nigeria