Dynamics of zinc accumulation in wheat grains grown in biological and conventional farming systems

[Truncated abstract] In the past, emphasis was placed on increasing grain production to feed the growing world population. The use of synthetic fertilizers, pesticides, mechanization and highyielding genotypes increased crop production and productivity after the Green Revolution. However, such practice resulted in low mineral content in edible crop parts. Among the minerals, zinc (Zn) is one of the most limiting in wheat grain. Also, more than 50 % of the world’s wheat growing areas are low in plant-available Zn, making Zn deficiency the most widespread micronutrient deficiency in crop production. Further, low plant available Zn in soils and drought resulted poor grain quality and quantity of wheat. Zinc plays a crucial role in plant metabolic and physiological processes, with low Zn not only reducing crop production but also decreasing the nutritional quality of edible plant parts. In addition, phytate in grain of cereals inhibits Zn absorption in human body. Therefore, increasing grain Zn density as well as lowering phytate concentration in wheat grain is important for increasing the bioavailability of Zn for improved human nutrition. This research provides detail information on distribution of Zn fractions in soils from biological and conventional farming systems, the role of soils in grain Zn concentration, the effects of Zn and phosphorus (P) nutrition on grain phytate and Zn concentrations, the relationship between nitrogen (N) fertilization and grain Zn concentration, and the effect of Zn nutrition on terminal drought tolerance in wheat. A sequential extraction method was used to fractionate soil Zn into water-soluble, exchangeable, specifically-adsorbed, acid-soluble, manganese-oxide-occluded, organic matter-occluded, amorphous iron (Fe)-oxide-bound, crystalline Fe-oxide-bound, and residual forms in soils from biological and conventional farming systems in Dalwallinu and Merredin, Western Australia.