Phosphorus management in pigeonpea (Cajanus cajan) – wheat (Triticum 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 P/ha to optimize the P requirement in pigeonpea [Cajanus cajan (L.) Millsp.]-wheat [Triticum aestivum L. emend. Fiori & Paol.] cropping system. This study revealed that 17.2 kg P/ha to pigeonpea recorded higher mean growth (plant height, 158.7 cm; branches/plant, 22.9 leaf-area index, 2.20), yield attributes (pods/plant, 194.5; grains/pod, 4.45; 1,000-grain weight, 74.45 g) and grain yield (2.05 Mg/ha) over no P and phosphate-solubilizing bacteria (PSB) alone. Application of 17.2 kg P/ha to the preceding pigeonpea also increased the mean growth (plant height, 72.7 cm; tillers/m row length, 101.1; LAI, 3.11) and yield attributes (spikes/m row, 91.8; grains/spike, 33.4), and also grain yield of the succeeding wheat (4.55 Mg/ha) compared with no P to pigeonpea Besides residual P, direct application of P to wheat up to 17.2 kg P/ha + PSB also increased the mean growth yield attributes and grain yield (4.85 Mg/ha) of wheat. Residual as well as direct-applied P up to 17.2 kg/P ha + PSB increased the total productivity of the cropping system in terms of pigeonpea-equivalent yield (residual, 4.48 Mg/ha; direct, 4.37 Mg/ha) over the preceding P levels. The cropping system removed the highest mean total P (26.8 kg/ha) when both the crops received 34.4 kg P/ha. The soil available P status after the cropping cycle improved over the initial status (10 kg/ha) with increasing rates of P application up to 34.4 kg/ha (18.8 kg/ha). However, negative balance of soil P (8.8 kg/ha) was noticed in the plots receiving no P.