Impact of plastic sheet mulching on grain Zn concentration, P/Zn ratio and Zn uptake in dryland grown winter wheat

Abstract

High yield and grain quality are the targets in wheat production. Plastic sheet mulching has improved wheat grain yield in under dryland agriculture, but its impact on grain quality, particularly grain zinc (Zn) concentration is not well known. Seven-site field experiments were conducted during 2014–2016 on drylands of three provinces in the Loess Plateau of China to examine the effect of plastic sheet mulching on wheat grain Zn concentration under different N applications. A split-plot design was adopted with the two main plots (no mulching and plastic sheet mulching) and the subplots with different N application rate. Measurements of Zn uptake, Zn remobilization, Zn distribution to the grain and bioavailability were made, together with biomass, yield and yield components. Study found plastic sheet mulching reduced the grain Zn concentration, and increased the molar ratio of P/Zn, decreasing the Zn bioavailability. Plastic sheet mulching also increased the aboveground Zn accumulation at anthesis by 14.4 %, the straw Zn accumulation at maturity by 14.8 % and the Zn remobilization to the grain by14.2 % but did not affect the availability of soil Zn. For each 100 kg N ha −1 applied under plastic sheet mulching, the grain Zn concentration, the Zn requirement, the aboveground Zn accumulation and remobilization to the grain increased by 3.6 mg kg −1 , 2.8 g Mg −1 , 6.6 g ha −1 and 3.8 g ha −1 , respectively. Aboveground Zn accumulation at maturity and post-anthesis Zn uptake varied with N rates in a linear-plus-plateau model. The reduction in post-anthesis Zn uptake and Zn harvest index were the factors leading to the decrease in grain Zn concentration under plastic sheet mulching. Consequently, under plastic sheet mulching, a rational N fertilizer strategy should be considered to improve the grain Zn concentration in wheat grown in dryland. • Plastic sheet mulching reduces wheat grain Zn bioavailability. • Post-anthesis Zn uptake and Zn harvest index influence wheat grain Zn content. • Rational N fertilization can improve grain Zn content and bioavailability in wheat. • Grain Zn content increased linearly with glutenin content in wheat grain.