Towards the More Efficient Use of Water and Nutrients in Food Legume Cropping

Abstract

Nutrient imbalance and soil moisture stress are the major abiotic constraints limiting productivity of cool season food legumes. These constraints are more pronounced in the semi-arid tropics and sub-tropics which are the principal production zones of chickpea, lentil and faba bean. The legumes are generally grown on residual moisture as a mono crop and consequently face drought especially during the reproductive phase. In recent years, chickpea, lentil, peas and faba bean have been grown in some areas with an irrigated/assured water supply under intensive cropping to sustain cereal based systems.

An increased water supply favourably influences productivity in dry environments. Faba bean, French beans and peas show a relatively better response to irrigation. The pod initiation stage is considered most critical with respect to moisture stress. Excessive moisture often has a negative effect on podding and seed yield. Eighty to ninety percent of the nitrogen requirements of leguminous crops is met from N₂ fixation hence a dose of 15–25 kg N ha^-1 has been recommended. However, in new cropping systems like rice-chickpea, higher doses of 30–40 kg N ha^-1 are beneficial. Phosphorus deficiency is wide spread and good responses occur to 20 to 80 kg P₂O₅ ha^-1, depending on the nutrient status of soil, cropping systems and moisture availability. Response to potassium application is localized. The use of 20–30 kg S ha^-1 and some of the micronutrients such as Zn, B, Mo and Fe have improved productivity. Band placement of phosphatic fertilizers and use of bio-fertilizers has enhanced the efficiency of applied as well as native P. Foliar applications of some micronutrients have been effective in correcting deficiencies. Water use efficiency has been improved with some management practices such as changed sowing time, balanced nutrition, mulching and tillage.