Increasing zinc concentration in maize grown under contrasting soil types in Malawi through agronomic biofortification: Trial protocol for a field experiment to detect small effect sizes

Summary

This trial protocol describes a multi-site field experiment designed to evaluate the potential of agronomic biofortification—zinc-enriched fertiliser application—to increase zinc concentration in maize grain across contrasting soil types in Malawi. The study addresses widespread micronutrient deficiency in rural populations by testing whether zinc fertiliser application creates sufficient increases in grain zinc concentration to improve dietary zinc supplies, with particular attention to soil-type-dependent effectiveness. The experimental design uses power analysis to detect a minimum 10% increase in zinc concentration at the highest fertiliser rate.

UK applicability

The findings may have limited direct applicability to UK cereal production, where zinc deficiency in staple crops is less prevalent and agricultural intensification typically includes micronutrient supplementation. However, the methodological approach to detecting small effect sizes in biofortification interventions could inform UK research on crop nutrient density optimisation.

Key measures

Grain zinc concentration, grain mass (yield), stover mass, stover zinc concentration across three zinc fertiliser rates (1, 30, and 90 kg/ha) in two soil types (Lixisols and Vertisols)

Outcomes reported

The study protocol describes a field experiment measuring grain zinc concentration, grain yield, and stover mass in maize grown under three zinc fertiliser application rates across two soil types at three sites. A second cropping year will assess residual benefits to grain zinc concentration.

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