Selenium application methods and rates for biofortification o common bean and their residual effects on Mombasa grass

Context. Agronomic biofortification is recognised as being an important strategy to increase selenium (Se) contents in food crops. The effectiveness of agronomic biofortification may differ depending on the methods of how Se is applied in agricultural systems. Aims. This study aimed to evaluate different Se application methods (involving Se addition in the soil via Se-enriched fertilisers and foliar Se application) and rates for biofortification of common bean and to assess residual effects of soil Se additions for biofortification of Mombaga grass grown after the common bean. Methods. Both experiments were carried out in a greenhouse. In the first cultivation (common bean), Se (as sodium selenate) was added at 0.0, 0.2, 0.4, 0.6, and 0.8 mg/dm(3) using six different methods, as follows: Se-enriched monoammonium phosphate, Se-enriched urea, Se-foliar application, Se-enriched monoammonium phosphate + Se-enriched urea, Se-enriched monoammonium phosphate + Se-foliar application, and Se-enriched urea + Se-foliar application. To evaluate the residual effects of soil Se additions, Mombaga grass plants were grown after the common bean (second cultivation) without additional Se supply. Key results. Agronomic biofortification effectiveness varied among methods, with higher Se contents in common bean grains being found when Se-enriched urea, Se-foliar application, and the combination of both methods were applied. Conclusions. Selenium addition methods via soil using fertilisers as carriers to add Se, including Se-enriched monoammonium phosphate, showed a potential of residual effects on succeeding crops since these methods were efficient for increasing Se contents in Mombaga grass shoots.