Nitrogen economics through intercropping of pigeonpea in rainfed sorghum.

In trials in 1975-8 under semi-arid conditions (av. rainfall 796 mm; mostly received during June-Sept.) in Rajasthan with sorghum and pigeon pea grown in alternate rows 30 cm apart and given 0-75 kg N/ha alone and with 40 kg P2O5 and P + 40 kg K2O/ha, increasing the N rates increased grain yields of sorghum, but decreased seed yields of pigeon pea; P and PK had no effect. As there was no significant difference in sorghum yields between N rates of 25 and 50 kg/ha and between 50 and 75 kg N/ha, the opt. N rate for the mixture under rain-fed conditions was 25-50 kg/ha instead of the recommended rate of 75 kg N/ha for sorghum in pure stands. N added to soil through leaf litter of pigeonpea after harvesting was 10-40 kg/ha in different treatments