Paddy management controls potassium release from minerals in purple soils after 40 years of cultivation

Abstract

AbstractThis study explored the mechanisms underlying the release and transformation of potassium from potassium‐rich minerals in paddy soils derived from purple soils. While potassium is abundant in these minerals, it is typically insoluble and inaccessible to plants. The agricultural practices employed in paddy soils may activate insoluble mineral potassium, potentially reducing potassium fertilizer applications. The activation of mineral potassium not only helps alleviate the dependence on soluble potassium fertilizers in rice cultivation, but also contributes to enhancing food security and sustainable agricultural development. Despite these potential benefits, the transformation pathways of mineral potassium in paddy soils remain unclear, posing an important science question that requires further investigation. This study collected data from a long‐term fertilizer experiment of paddy soils derived from purple soils with abundant potassium‐rich minerals (1982–2019, rice‐wheat rotation). The results revealed that paddy management could drive the transformation of potassium in illite minerals in paddy soils and meet the long‐term growth needs of crops. Submergence reduction significantly increased the concentration of positive ions such as Fe2+ and Ca2+ and provided a pathway for the free movement of ions, promoting the substitution of these ions with interlayer potassium of minerals. This substitution and alternating reduction and oxidation conditions played an important role in the transformation of potassium in illite minerals. The study indicates the promising potential for using crushed illite rocks in rice paddies as a substitute for traditional potassium fertilizers.