Impact of long-term phosphorous fertilization on Olsen-P and grain yields in maize-wheat cropping sequence

摘要

Due to generally low phosphorus (P) recovery efficiency in maize-wheat cropping systems in northwest India, farmers have over-applied P fertilizers over many decades to improve crop growth and increase profitability. This practice caused a considerable part of cultivated land to have 'very high' (> 50.0 kg P ha(-1)) Olsen-P values in soil. This study was aimed at finding critical concentrations of Olsen-P for maize (Zea mays L.) and wheat (Triticum aestivum L.) sequence for effective utilization of buildup P and optimal P rates for maintaining critical Olsen-P in soil in this region by utilizing one long-term (11 years) and 2 short-term (3 years) trials. Long-term studies in high Olsen-P soils showed increased P buildup with present recommended fertilizer P application rates of 26 kg ha(-1) to both crops. With no P application, Olsen-P values in soils decline at rate of 3.0 kg P ha(-1) year(-1). For sustaining maize and wheat yields, critical concentrations of Olsen-P obtained from different statistical models (linear plateau, quadratic plateau and exponential) range from 36.7 to 50.0 kg P ha(-1) for maize and 39.4-57.1 kg P ha(-1) for wheat and 38 kg P ha(-1) for both crops using Cate and Nelson split method. The use of Mitscherlich equation for determining the 'effective' P and Olsen-P requirement for getting higher yields was found to be a better method compared to above-mentioned statistical and graphical methods. Mitscherlich equation estimates the amount of P applied to achieve the desired Olsen-P levels in soil.