Agronomic biofortification of soybean with selenium via foliar application

Abstract

Selenium (Se) is a key component of selected amino acids and an important micronutrient for humans and animals, yet in several countries - Brazil included - soil Se concentrations are very small, which often leads to low Se content in feed and food. To overcome this problem, different agronomic strategies have been proposed for various crop plants, especially the protein-rich ones, e.g., soybean. This work aimed to evaluate the effect of sources and doses of Se, associated or not with a fertilizer aimed at improving nutrient translocation (FIT), upon grain yield and Se content in soybean. In order to evaluate the potential of soybean as a Se seed-accumulating species and also the association of sodium selenate as well as alternative sources of Se (organic Se compounds) with FIT, different experiments were conducted under greenhouse conditions. The first sequence of experiments consisted of two trials evaluating doses of sodium selenate (SS) and SS+FIT, and the second sequence of experiments assessed the effect of four sources of Se, associated or not with FIT. Plant parts (grains, leaf, stem and pods) were separated in order to obtain dry mass and their content of Se, which was determined by atomic absorption spectrophotometry with graphite furnace atomization, after acid digestion of the vegetal tissue. Foliar application of Se did not affect grain yield and dry mass in all experiments. Total Se content in grain, leaf, and pod plant parts increased linearly as a function of the applied doses of SS, yet the association of SS with FIT did not alter this parameter. Leaf had higher contents of Se, when compared with other plant parts. In the 1st experiment, the average recovery of Se in the grain was 23.6%, while in the 2nd experiment, it was 26.6%. Foliar application of alternative sources of Se, associated or not with FIT, resulted in significant increases in Se content in grain, leaf, and pod plant part, but the stem presented Se content. The SeM1 source presented potential for use in agronomic biofortification practices, especially when associated with FIT. Our findings revealed that the foliar application of Se in soybean is an efficient approach for production of biofortified food and that the use of organic Se compounds may be a strategy to increase the effectiveness of the agronomic biofortification of soybean grains with selenium.