Effect on nitrogen economy, productivity and energetics of wheat (Triticumaestivum) under double cropping systems

A field experiment was conducted during 1994-96 to study the effect of rain y season (kharif) crops on the productivity, energetics and nitrogen econom y of succeeding wheat ( Triticum aestivum L. emend. Fiori & Paol.) under do uble cropping systems. Among the rainy season crops, redgram (Cajanus cajan L. Millsp.)+ blackgram (Phaseolus mungo L.) at 2:2 paired row ratio record ed the highest yield on wheat equivalent basis ( 2 2 10 kg/ha). Wheat succe eding redgram + blackgram performed better with maximum grain yield ( 3 695 kg/ha). With the highest quantity of total wheat equivalent yield (6 905 k g/ha), net return (Rs 18 298/ha), return/rupee invested (Rs 2.02), producti on efficiency (25.6 kg/day/ha), energy output (189 851 MJ/ha), energy outpu t : input ratio (7.92), energy-use efficiency (29 kg/100 MJ) and N-uptake ( 29.93 kg/ha) redgram + blackgram - wheat sequence appeared to be economical ly and energetically viable sequence followed by redgram- wheat sequence in sandy loam soils. Application of 80 kg N/ha to wheat recorded maximum whea t yield (4 319 kg/ha), total wheat equivalent yield( 6 638 kg/ha), net retu rn (Rs 12 55 l /ha), return/rupee invested (Rs 1.70), production efficiency (28.5 kg/day/ha), energy output : input ratio (7.91) and energy-use effici ency (26 kg/100 MJ). At the optimum production level of wheat after fellow (4 282.68 kg/ha) the highest quantity of 38.76 kg N/ha could be saved in wh eat succeeding redgram + blackgram.