Agronomic biofortification of maize with selenium (Se) in Malawi

Suboptimal dietary Se intake is widespread in Malawi due to low levels of plant-available Se in most soils and narrow food choices. The aim of this study was to determine the potential for biofortifying maize using Se-enriched fertilisers in Malawi. The response of maize to three forms of selenate-Se fertiliser was determined. Crops were treated with a liquid drench of Na2SeO4(aq) (0–100 g Se ha−1), a compound NPK + Se fertiliser (0–6 g Se ha−1), or Se-enriched calcium ammonium nitrate (CAN + Se; 0–20 g Se ha−1). Experiments with Na2SeO4(aq) and NPK + Se were conducted at six field sites, and at a subset of three sites with CAN + Se, in 2008/09 and 2009/10 (i.e. 30 experimental units). The increase in grain Se concentration was approximately linear for all Se forms and application rates (R2 > 0.90 for 27 of the 30 experimental units). On average, whole-grain Se increased by 20, 21 and 15 μg Se kg−1for each gram of Se applied as Na2SeO4(aq), NPK + Se and CAN + Se, respectively. Grain and stover yields were unaffected by Se applications. An application of 5 g Se ha−1 to maize crops in Malawi would increase dietary Se intake by 26–37 μg Se person−1 d−1 based on national maize consumption patterns. Agronomic biofortification with Se in Malawi is feasible in theory through the existing national Farm Input Subsidy Programme (FISP) if deemed to be economically and politically acceptable.

► The response of maize to selenate-Se containing fertiliser was determined in Malawi. ► Grain Se concentration increases were linear for all Se forms. ► Se-biofortification in Malawi is feasible through existing fertiliser subsidies.