Agronomic biofortification of maize, soybean and groundnut with selenium in intercropping and sole cropping systems

Agronomic biofortification of staple food crops with micronutrients important for human nutrition, such as selenium (Se), is currently being advocated to address widespread deficiencies in the diets of populations in sub-Saharan Africa. Previous research has shown that there is likely to be widespread dietary Se deficiency in Malawi due to low concentration of Se in edible parts of the staple crops, such as maize (Zea mays L), on low-pH soils, but that this could be addressed through agronomic biofortification using Se-enriched fertilisers. Farmers often intercrop maize with legumes such as groundnut (Arachis hypogaea) and soybean (Glycine max). Therefore, a field study during the 2012/2013 cropping season examined the effect of foliar application of Se on its concentration in grains and stover of maize, soybean and groundnut grown as intercrops or sole crops at three sites in Malawi. Mean Se concentrations were highest in soybean seed, followed by groundnut seed and maize grain, both in plots with added Se and without. Application of 10 g ha-1 of Se increased Se concentration in maize grain by 8-fold, in groundnut seed by 9-fold and in soybean seed by 18-fold; thus universal adoption could increase estimated average dietary Se supply in Malawi from between 21 and 31 µg cap-1 d-1 to between 68 and 78 µg cap-1 d-1.