Time-dependent application strategies of selenium Nanofertilizer to enhance biofortification in rice and wheat

Understanding the effects of different fertilization timing on crop selenium biofortification is of great importance. This field study evaluated the effects of Se nanoparticle application at different growth stages on crop yield, Se accumulation, and Se speciation. Se NPs application at the jointing stage significantly increased grain yield (up to 10.2 % in rice, 8.4 % in wheat) and Se concentration (9.7-fold in rice, 21-fold in wheat). Rice showed higher Se uptake efficiency, while wheat exhibited greater translocation of Se from leaves to grains. Notably, Se NPs were absent from grains in both rice and wheat, ensuring food safety. Selenomethionine was the dominant Se species in both grains (>62 %), unaffected by fertilization timing. Delayed fertilization increased Se retention in the wheat inner fraction, enhancing Se recovery during flour processing. These findings offer practical guidance for optimizing Se biofortification strategies to improve grain Se content and nutritional quality.