Phosphorus nutrition of wheat under cotton-wheat cropping system

The experiment was carried out in complete randomized block design with three replications and four treatments. The treatments were 0, 30, 60 and 90 kg P2O5 per ha and N was applied as a basal close at the rate of 120 kg per ha. However, K was not applied, as it was adequate in soil. The soil was analyzed for its physicochemical characteristics, before and after harvesting of the crop. The N fertilizer was applied in the form of urea in three equal split doses, first at the time of sowing and second at the time of first irrigation and third at the time of second irrigation. Phosphorus was applied in form of SSP at required rate at the time of sowing. The soil analysis before sowing of experiment revealed that the soil was heavy in texture, non-saline (EC=0.83 dSm-1), alkaline in reaction (pH=7.75), moderately calcareous (lime = 10.00%), medium in organic matter (01.21 %) and AB-DTPA extractable P (4.06 mg per kg) and K (100mg per kg). However soil analysis after harvest of crop indicated that the P content increased with increasing rate of P. The maximum increase (40%) of residual P was observed in plots receiving 90 kg P2O5 per ha. Fertilizer application has significantly increased grain and straw yield. The significant effect of P in case of grain and straw was up to 60 kg P2O5 per ha. At this level of P application, increase in grain yield over control was 78% and in case of straw the increase over control was 75%. Phosphorus content in wheat (leaf-booting stage), grain and straw showed gradual increase. However, the effect was statistically non-significant. Seed index (1000-grain weight) gradually increased with increased rate of P but the effect was statistically non significant. It was concluded that soil P application had significant effect on physiological and chemical characteristics of wheat. Moreover P application in wheat beyond 60kg P2O5 per ha remained statically uneconomical.