Grain iron and zinc concentrations of wheat and their relationships to yield in major wheat production areas in China

Maintaining adequate mineral content in wheat (Triticum aestivum) grain is critically important for human nutrition. In this study iron (Fe) and zinc (Zn) concentration, and grain yield of 655 field-grown wheat samples from major wheat production areas of China were investigated from 2009 to 2011. Grain yields were found as high as 5423 and 6565 kg ha−1 for spring and winter wheat, respectively, with a corresponding grain Fe concentration of 48.2 and 45.1 mg kg−1, and Zn concentration of 30.4 and 30.3 mg kg−1. Compared to the recommended grain nutrient concentrations, 63% and 72% of the spring and winter wheat samples were considered Fe inadequate, and 88% and 87% were Zn inadequate, respectively. Regionally, grain Fe and Zn concentration was found to be lower in high-yielding regions. Grain Fe concentration was significantly and positively correlated with Zn concentration for both spring and winter wheat. For each 1 mg kg−1 increase in grain Zn, the Fe concentration increased by 0.6 and 0.3 mg kg−1 for spring and winter wheat, respectively. However, the Fe and Zn concentration was significantly and negatively correlated with grain yield: for every 1000 kg ha−1 increase in grain yield, the Fe concentration decreased by 2.1 and 1.3 mg kg−1 for spring and winter wheat, respectively, and the Zn concentration decreased by 0.9 and 1.3 mg kg−1, respectively. Therefore efforts to simultaneously increase grain yield and Fe and Zn concentration in wheat grain remain a challenging endeavour for wheat farmers.