Long-term straw removal and double-cropping system reduce soil cadmium content and uptake in rice: A four-year field analysis

Several studies have demonstrated that reintroducing crop straw to fields may intensify cadmium (Cd) contamination in agricultural soils. However, the specific effects of long-term straw management practices on Cd concentration and its bioavailability in soil-rice ecosystems remain unclear. In this context, to explore the influence of straw return (SR) and straw removal (NSR) on Cd accumulation in both soil and rice within a double-cropping system, we conducted a four-year field study. Our research study unveiled that NSR consistently decreased soil Cd concentration and its bioavailability by approximately 16.93%–27.30% and 8.23%–21.05% respectively across both study sites. Conversely, SR resulted in a substantial increase in soil Cd bioavailability, ranging from 38.64%–53.95%. Notably, compared to NSR, SR significantly increased total soil Cd by 5.47%–36.58% and increased Cd content in brown rice by 8.00%–100.24%. Remarkably, after four consecutive years of NSR, brown rice Cd concentration at the Changfeng site compiled with national safety standards (GB 2762–2022). Additionally, returning early rice straw significantly raised soil Cd bioavailability for the subsequent crop, more so than late rice straw did for the early rice the following year. The findings suggest that traditional double-cropping cultivation with straw removal can effectively mitigate Cd contamination risks in crops and farmland in Hunan Province.