Response of pigeonpea (Cajanus cajan) to sources and levels of phosphorus under rainfed condition

A field experiment was conducted during rainy seasons of 1999 and 2000 to study the effect of sources and levels of phosphorus on productivity of pigeonpea [Cajanus cajan (L.) Millsp.]. Application of single superphosphate (SSP) produced significantly higher nodules/plant, dry weight of nodules/plant and pods/plant than that of diammonium phosphate (DAP). Application of SSP increased the seed yield, total P uptake and net returns over their respective DAP respectively by 6.1%, 0.53 kg P2O5/ha and Rs 913/ha. Phosphorus application increased the nodules/plant, dry weight of nodules/plant, pods/plant, seed yield, total P uptake and net returns significantly. Seed yield and net returns increased significantly with P levels up to 40 kg P2O5/ha, giving 52.4 and 18.3% and Rs 6,757 and Rs 3,002/ha more over the control and 20 kg P2O5 respectively. Returns/Re invested was recorded more under 60 and 80 kg P2O5/ha (Rs 2.76), followed by 40 kg P2O5/ha (Rs 2.66). The agronomic P-use efficiency (APUE) and apparent P recovery were higher in SSP; however, these were recorded more at lower level of P and decreased with increase in P level. The physiological efficiency of phosphorus (PEP) and phosphorususe efficiency (PUE) were calculated more in DAP. However, PEP increased with increase in P level.