Productivity and nutrient balance of maize (Zea mays) plus blackgram (Phaseolus mungo) intercropping as affected by fertilizer and plant density management of blackgram

A field experiment was conducted during the rainy season of 1988 and 1989 t o study the productivity and changes in soil fertility by maize (Zea mays L .) + blackgram (Phaseolus mungo L.) intercropping on sandy-loam soil having low fertility. Separate fertilization (fertilizer of component crops appli ed separately to respective rows) resulted in 8.4% higher maize grain yield than uniform fertilization (fertilizer of component crops mixed together a nd applied uniformly in rows irrespective of crops). Reduction in populatio n of blackgram as-an intercrop below 100% decreased the productivity of the system. Grain yield of intercropped maize was almost similar (4.04-4.18 to nnes/ha) with blackgram yield of 0.82-0.84 tonne/ha and maize-equivalent yi eld of 5.88-5.96 tonnes/ha to its sole crop (4.32 tonnes/ha) when grown wit h 100% population (20 kg seed/ ha) and 50-100% fertilizer (20 kg N and 17.6 kg P/ha) to blackgram and component crops fertilized separately indicating that 50% fertilizer to blackgram could be saved without any significant re duction in production potential of the system. Total P uptake in maize + bl ackgram intercropping decreased by 16-18% in maize and 40-50% in blackgram compared with sole cropping. Maximum gain in soil-available N (32.1 kg/ha/y ear) was under the intercropping system with 100% population and 50% fertil izer of blackgram and in available K (47.4 kg/ha/year)with 100% population- fertilizer of blackgram. Separate fertilization to both the component crops had an edge over uniform fertilization for gain in soil-available N and K.