Moisture conservation and nitrogen recycling through legume mulching in rainfed maize (Zea mays)-wheat (Triticum aestivum) cropping system

Mulching with vegetative materials is a highly beneficial and widely-investigated agro-technique in rainfed areas but the adoption of this practice has been constrained due to non-availability of mulch biomass locally. Live mulching with fast-growing annual green manure legumes like sunnhemp (Crotalaria juncea) or prunings of Leucaena leucocephala grown as hedge rows can be done for moisture conservation as well as nutrient cycling in the maize-wheat cropping system, which is predominantly followed in the high rainfall sub-mountainous region of north-western India. A field experiment was conducted at Selakui, Dehradun during 2000-2004 to study the effect of legume mulching, viz. in situ grown sunnhemp and Leucaena prunings, along with varying N levels, viz. 0, 30, 60 and 90 kg N ha⁻¹ (to maize), and 0, 40 and 80 kg N ha⁻¹ (to wheat) on productivity, soil moisture conservation and soil physico-chemical properties. Intercropped sunnhemp added 0.75-1.45 t dry matter and 21.6-41.3 kg N ha⁻¹ at 30-35 days, while Leucaena twigs added 1.89-4.15 t dry matter and 75.2-161.3 kg N ha⁻¹ at 60-65 days of maize growth. Live mulching with sunnhemp or Leucaena biomass improved soil moisture content at maize harvest (+1.15-1.57%) and crop productivity by 6.8-8.8% over no mulching. Combined use of both the mulching materials was more effective in improving the soil moisture content (+2.08-2.29%) and grain yield (15.1%) over their single application. Response of maize to N fertilizer application was significant up to 90 kg N ha⁻¹, and it was relatively more pronounced under the mulching treatments. Residual effect of mulching on wheat showed an increase in yield of 10.2% with sunnhemp or Leucaena, and 27.9% with sunnhemp + Leucaena. There was an improvement in organic C and total N status of soil, and a decrease in bulk density associated with an increase in infiltration rate due to mulching at the end of 4 cropping cycles. It was concluded that legume mulching is a highly beneficial practice for enhanced moisture and nutrient conservation, leading to increased productivity and soil health of maize-wheat cropping system under Doon valley conditions of north-western India.