Optimizing phosphate fertilization in relation to phosphorus supply capacity of soils in Yunnan maize producing areas

Objectives The aim of this study was to establish an optimum P application rate for maize production on the long-existing low and middle P-containing farmlands in Yunnan, in order to reduce the potential of phosphorus leaching risk to surface water environment.

Methods Field experiments were conducted respectively in Xundian (middle soil Olsen-P level) and Xiaoshao (low soil Olsen-P level), Yunnan Province consecutively from 2017 to 2019. The P₂O₅ treatment levels were 0, 45, 90, 135, and 270 kg/hm² in Xundian, and 0, 60, 90, and 120 kg/hm² in Xiaoshao. Maize yield, P uptake at the main growth stages, and the allocation in grains at maturation stage were investigated. The optimal P rate was calculated using lineal-plateau model.

Results Across the three years, P application significantly increased maize yield. P90 recorded the highest yield in both field sites. P270 in Xundian and P120 in Xiaoshao elicited significantly lower yield than P90. In Xundian, P45 and P90 recorded similar maize P uptake and accumulation, those were significantly higher than P135 and P270. In low Olsen-P soil of Xiaoshao, the maize P uptake improved at increasing P rates, however, the grain P accumulation was not significantly different between P90 and P120. The simulated yield under different P application rates by lineal-plateau model revealed extreme significance (P<0.001). The calculated optimum P₂O₅ application rates were 65.6 and 93.7 kg/hm² for moderate and low Olsen-P soil, respectively.

Conclusions Compared with the recommended P₂O₅ rate for maize production in Yunnan, the optimum P₂O₅ rate should be reduced to 65.6 kg/hm² in moderate Olsen-P soil, and slightly increased to 93.7 kg/hm² in low Olsen- P soil.