Agronomic threshold of soil available phosphorus in grey desert soils in Xinjiang, China

Based on 23 years of data, yields of maize, wheat and cotton were modelled under different fertilizer management practices and at different levels of available phosphorus (Olsen-P) in soil. Three types of threshold models were used, namely linear-linear (LL), linear-plateau (LP), and Mitscherlich type exponential (Exp). The agronomic thresholds of available phosphorus were 25.4 mg.kg(-1) for cotton, 14.8 mg.kg(-1) for wheat, 13.1 mg.kg(-1) for maize and 25.4 mg.kg(-1) for the grey desert soil regions of Xinjiang in China as a whole.