Comparison of potential potassium leaching associated with organic and inorganic potassium sources in different arable soils in China

Abstract

Potassium (K) leaching is detrimental to the maintenance of sustainable arable soil K fertility, especially in low-K fixation soils. It is not known whether the application of inorganic fertilizers with lower K mobility or crop straw can reduce potential K leaching in low-K fixation arable soils. The potential K leaching of 14 representative arable soils with different K fixation capacities in China was evaluated with or without the addition of K under two rainfall intensities (90 and 225 mm), and then potential K leaching was assessed in relation to five K sources (KCl, K2SO2, KH2PO2, maize (Zea mays L.) straw, and rice (Oryza sativa L.) straw). Without K addition, K leaching mainly occurred in sandy soils at 90 mm of rainfall and in soils with greater organic matter at 225 mm of rainfall. With K addition, the leaching percentage of exogenous K ranged from 0.6% to 11.6% at 90 mm of rainfall and 1.2% to 21.2% at 225 mm of rainfall. The greatest K leaching occurred in soils with fewer K-bearing minerals and lower pH at both rainfall intensities. In most cases, KH2PO2, which has lower K mobility, markedly reduced K leaching in both high- and low-K leaching soils at the two rainfall intensities. Maize and rice straw reduced K leaching only in soils with high K leaching, regardless of rainfall amount, whereas more K was leached in soils with lower K leaching at high rainfall intensity. In conclusion, KH2PO2 and straw should be preferred for reducing K leaching in low-K fixation arable soils.