Important crops which are suitable for green manuring are: 1. Dhaincha (Sesbania Aculeate) 2. Sunhemp (Crotalaria Juncea) 3. Barseem (Trifolium alexandrinum) 4. Senji (Melilotus parviflora).
1. Dhaincha (Sesbania Aculeate):
It is suitable for orchards on heavy soils (loam-clay). It is resistant to drought as well as stagnation of water.
Dhaincha grows well in alkaline soils and corrects alkalinity if repeatedly grown for 4-5 years. The roots have plenty of nodules. It yields 12-15 tonnes of green manure per hectare. A seed rate of 35-40 kg/ha will be sufficient. Ploughing may be done after 40-45 days of sowing. Application of 25kg diammonium phosphate at the time of sowing greatly improves the growth of dhaincha.
2. Sunhemp (Crotalaria Juncea):
It is a quick growing green manure crop. It can be ploughed after 40-45 days of sowing. It cannot withstand heavy irrigation. A good stand of crop may provide 13-16 tonnes of green biomass per hectare. Seed required for sowing one hectare is 30-35 kg.
3. Barseem (Trifolium alexandrinum):
Barseem is grown in almost all kinds of fruit crops expect peaches. Two to three cuttings are taken before it is finally ploughed in the orchards. 18-20 kg of seed is required per hectare. It yields more than 10 tonnes of green biomass per hectare. In addition to green matter it adds sufficient beneficial microorganisms.
4. Senji (Melilotus parviflora):
It is an important green manure crop of orchards. It is usually sown in October-November and 20-25kg of seed is sufficient to sow one hectare. It can add more than 20 tonnes of green biomass. If seed ripens it sheds itself and grows of its own to a number year in orchards and add microbes through nodules.
Green manuring maintain the fertility of the orchard soil. The annual application of fertilizer doses to the fruit plants can be reduced to a great extent. Green manures check the leaching of nutrients by the addition of humus. Humus is highly colloidal and amorphous in nature. The cation exchange capacity and water holding capacity of soil with the increase of humus increase to a great extent. Dependence on the farm yard manure shall be reduced, which is too short of the requirement.
Ploughing a leguminous crop shall improve organic matter and nitrogen content of soil. It has been estimated that addition of two tonne of green manure dry matter per acre would add forty kilograms to fifty kilograms of nitrogen. Green manuring crop take up the soluble constituents from soil, those might otherwise have least through soil erosion or leaching. Green manuring crop also acts as a cover crop in orchards.