Effective potassium management for sustainable crop production based on soil potassium availability

Potassium (K) is an essential macronutrient for sustainable crop production. The impact of exogenous K input on soil K apparent balance has been increasingly investigated; however, the effects of K input on K reserves and crop yields in soils with different characteristics are not well understood. This study conducted a six-season crop field experiment at Quzhou site (QZ), a region with inherently high soil K availability, and Liaocheng (LC) site, a region with low soil K availability. It examined the impacts of K fertilizer application, with straw retention and straw removal, on soil K reserves and yield sustainability of winter wheat-summer maize in the North China Plain. The results indicated that co-application of K fertilizer and straw did not influence crop annual yield at QZ but significantly increased yields by 21 % at LC, and the co-application did not significantly affect the sustainable yield index at both sites. Crop K uptake was higher at QZ than at LC and was increased by straw retention at both sites, suggesting straw is a vital supplement for promoting K uptake. NH₄OAc-extractable K was most abundant in the topsoil but was likely translocated to deeper soil layers with higher K inputs, especially at the LC site. Slowly available K decreased for straw removal with no K fertilizer at both sites, but for application of 332 kg K ha⁻¹, the slowly available K remained unchanged at QZ and increased at LC. The recommended K fertilization rate of 112 kg K ha⁻¹ had no significant effect on soil NH₄OAc extractable K concentration at QZ but the increase in that concentration at LC was only observed with straw retention. In words, for soils initially rich in K, a sustainable K management strategy should consider adjusting K apparent balances based on K fertilizer prices. In contrast, for soils naturally deficient in K, enhancing soil K fertility through K fertilization is essential, alongside the strategic use of straw.