Effect of levels of phosphate and organic manures on phosphate supplying capacity and p-kinetics in wheat grown in a typic haplustept soil

A pot experiment with wheat (WH 542) as test crop was conducted in screen house on a Typic Haplustept surface (0–15 cm) soil of Haryana Agricultural University Farm, Hisar. Initial laboratory studies showed that around 30.4 to 63.2% of added P was found to retain by the soil and phosphate sorption (x/m) increased progressively with increase in solution P concentrations. Phosphate supplying capacity (PSC) based on quantity-intensity relationship over the days of wheat growth was found to increase significantly with increase in levels of added P. The decrease of PSC upto 30 days and variations thereafter, towards higher values upto 90 days at P₅₀ and P₁₀₀ levels of P application all throughout the growing periods of wheat growth was observed. FYM always showed significantly highest PSC over that of green manuring treatment. First order kinetic equations showed higher values of P content at 0 day (intercept) of crop growth and found to increase progressively with increasing levels of P along with organic manures. However, reverse trend was observed in second order kinetic constants. Strong and significant positive correlation between cumulative P desorbed and t^1/2 reflected that rate of release of P was synchronizing with time or rather a good state of equilibrium was achieved in relation to crop condition. Significantly highest dry matter yield and P uptake in the treatment receiving P @ 100 mg/kg soil was observed and indicated that phosphate utilization by the crop was solely governed by the process of diffusion. FYM towards dry matter yield and P uptake was significantly higher over that of green manures suggested that green manures could not be an alternate source of FYM towards better P uptake and dry matter yield in wheat crop.