Phosphorus management in pigeonpea (Cajanus cajan) - wheat (Tritcum aestivum) cropping system

A field experiment was conducted at New Delhi during 2002-03 and 2003-04 on sandy-loam soil with 10 kg available Plha to optimize the P requirement in pigeonpea [Cajanus cajan (L.) Millsp.1-wheat [Triticum aestivum L. emend. Fiori & Paol.] cropping system. This study revealed that 17.2 kg Plha to pigeonpea recorded higher mean growth (plant height, 158.7 cm; brancheslplant, 22.9 leaf-area index, 2.20), yield attributes (podslplant, 194.5; grainslpod, 4.45; 1,000-grain weight, 74.45 g) and grain yield (2.05 Mglha) over no P and phosphate- solubilizing bacteria (PSB) alone. Application of 17.2 kg Plha to the preceding pigeonpea also increased the mean growth (plant height, 72.7 cm; tillerslm row length, 101 .I; LAI, 3.1 1) and yield attributes (spikeslm row, 91.8; grainslspike, 33.4), and also grain yield of the succeeding wheat (4.55 Mglha) compared with no P to pigeonpea Besides residual P, direct application of P to wheat up to 17.2 kg Plha + PSB also increased the mean growth yield attributes and grain yield (4.85 Mglha) of wheat. Residual as well as direct-applied P up to 17.2 kg1P ha + PSB increased the total productivity of the cropping system in terms of pigeonpea-equivalent yield (residual, 4.48 Mglha; direct, 4.37 Mglha) over the preceding P levels. The cropping system removed the highest mean to- tal P (26.8 kglha) when both the crops received 34.4 kg Plha. The soil available P status after the cropping cycle improved over the initial status (10 kglha) with increasing rates of P application up to 34.4 kglha (18.8 kglha). However, negative balance of soil P (8.8 kglha) was noticed in the plots receiving no P.