Optimizing NPK fertilization for Se enrichment and Cd reduction in selenium-rich rice

Selenium (Se)-enriched rice fields encounter a risk of cadmium (Cd) contamination, which reduces the quality of rice safety. This study aimed to investigate the impact of nitrogen (N), phosphorus (P), and potassium (K) fertilizers application ratios on rice yield and the coexistence issue of Se and Cd in Se-rich paddy fields. And to explore the possibility of achieving high yield of rice with low Cd and high Se. An innovative “3517” fertilization experiment was conducted to explore the effects of N/P/K application on Se/Cd levels in the soil, stems and grains of rice at different growth stages, and to investigate the correlations among them. Furthermore, the multi-objective optimization model was adopted to analyze the optimal fertilization for the first time. Yield was significantly positively correlated only with N application, and the Se content in the soil was negatively correlated with the Cd content in grains. Regarding Se, N inhibited Se accumulation in grains, while P has a threshold effect and is positively correlated with Se in grains; K increases Se in grains to a certain extent. For Cd, an N application increased in content of Cd in grains, while P and K delayed the migration of Cd into grains and were positively correlated with Cd in straw. Optimal N/P/K combinations (codes 211 and 220) were identified, which can regulate the Se and Cd contents in rice with less fertilizer application. This provides feasible technical guidance for the safe production of Se-enriched rice.