Integrated phosphorus management in pigeonpea (Cajanus cajan) - wheat (Triticum aestivum) cropping system

A field experiment was conducted during 2005-06 and 2006-2007 at New Delhi in the rainy (kharif) and winter (rabo seasons on sandy-loam soil to assess the effect of sources and levels of phosphorus on pigeonpea [Cajanus cajan (L.) Millsp.] -wheat (Triticum aestivum L. emend. Fiori & Paol.) cropping system. Results revealed that application of P to pigeonpea at 34.4 kg/ha through single superphosphate + phosphorus-solubilizing bacteria (PSB) recorded higher mean yield attributes and grain yield (1.49 Vha) of pigeonpea and yield attributes and yield (4.49 Vha) of wheat over no P and 17.2 kg P/ha through single superphosphate alone or rock-phosphate + PSB. Direct application of P to wheat up to 34.4 kg P/ha improved the mean yield attributes and grain yield (4.53 Vha). The mean increase in wheat-grain yield due to P fertilization was 10.26 and 7.31% compared with that in the con- trol and 17.2 kg P/ha respectively. The system productivity (pigeonpea-equivalent yield) was the highest when pigeonpea and wheat received 34.4 kg P/ha through pressmud + PSB (4.06 Vha) and 34.4 kg P/ha (3.99 Vha) re- spectively. Application of 34.4 kg P/ha through single superphosphate with or without PSB or pressmud + PSB to pigeonpea recorded significantly higher P uptake by the system over rock-phosphate + PSB. The P balance in the soil increased with increase in P fertilization to the system.