Green manure effects on zinc and cadmium accumulation in wheat grains (<italic>Triticum aestivum</italic> L.) on high and low zinc soils.

Background and aims: Zinc (Zn) deficiency is a global problem in human nutrition due to imbalanced diets based on staple foods of low Zn contents. This study investigated the potential of using clover (<italic>Trifolium alexandrinum</italic> L.) and mustard (<italic>Sinapis alba</italic> L.) green manure crops to increase soil Zn uptake by wheat (<italic>Trifolium aestivum</italic> L.) without enhancing cadmium (Cd) accumulation.Methods: A factorial pot experiment with wheat was performed with three green manure treatments (clover, mustard or no green manure) and three soil treatments which were a high-Zn soil (FYM), a low-Zn soil (TURK) and the TURK soil with mineral Zn fertilization (TURK+ZN). Green manure crops were grown first and then incorporated into the soils before wheat.Results: In contrast to mustard, clover increased grain Zn concentrations in the FYM and TURK+ZN soils, but not in the TURK soil. The effect appeared to be due to high soil nitrogen inputs and concurrent pH decrease, root biomass increase, and the release of organic ligands mobilizing soil Zn and Cd. However, the high N inputs also induced Cd accumulation above critical thresholds.Conclusions: The study suggests that on Zn sufficient soils or in combination with Zn fertilizer, leguminous green manure can increase soil Zn accumulation by wheat. [ABSTRACT FROM AUTHOR]