Response of maize to different phosphorus levels under calcareous soil conditions.

A field experiment was conducted to investigate the effect of different levels of phosphorus on the yield and P uptake by maize [Zeamayscv Jalal) on calcareous soil (19% lime on w/w basis) of Peshawar soil series [Piedmont alluvium, silty clay loam, Ustochrept]. The P treatments included 0 (control), 45, 90, 135 and 180 kg as P2O5 ha -1 were arranged in randomized complete block design (RCBD) with three replications. The results showed that maize plant height, number of cobs plot -1 , grain and biomass yields increased with increasing levels of phosphorus. The increase in grain yield of maize over control was 17.8, 26.4, 50.6 and 47.1 % and biomass by 21.08, 37.06, 37.19, and 42.13 % with application 45, 90, 135 and 180 kg P2O5 ha -1 , respectively. The increase in yield and yield parameters above 135 kg ha -1 P application was non-significant, rather grain yield decreased when supplied with 180 kg P2O5 ha -1 . Tissue P concentration significantly increased with increasing levels of P but with variable pattern at all the given stages of the crop growth. During the initial growth viz. vegetative stage, the differences between control and P applied plots as well as among different P levels were more wider than latter stages that could be associated to the dilution effect or translocation of P from leaves to grains. Soil solution and AB-DTPA extractable P concentration determined at different stages of crop also tended to increase with increases in applied P levels. The VCR values revealed that P applied at the rate of 135 kg P2O5 ha -1 was economical with VCR of 3.41:1. Based on higher crop growth and yield and P concentration in tissue and soil, it was concluded that application of 135 kg P2O5 ha -1 could be the appropriate dose of P for maize under the prevailing highly calcareous soil conditions.