Abstract
Nitrogen (N) is critical for zinc (Zn) accumulation in winter wheat grain via enhancing Zn absorption into plant roots. This paper explored a possible mechanism for enhanced absorption of Zn in winter wheat by N combined with Zn application based on the Zn bio-availability in soil. A pot experiment with three N application rates (0.05, 0.2, and 0.4 g kg-1), two Zn application rates (0 and 10 mg kg-1), without and with plants was conducted. The results showed that high N (N0.2 and N0.4) combined with Zn (Zn10) application significantly increased the yield, yield components and Zn and N concentrations in winter wheat shoots and grain. The available Zn concentration in soil with and without plants was increased by N0.2Zn10 and N0.4Zn10 treatment at each growth stage. N0.2Zn10 and N0.4Zn10 treatment significantly decreased the pH in soil without plants but had different influences on the pH in soil with plants, which depended on the different N application rates and growth stages. Meanwhile, N0.2Zn10 and N0.4Zn10 treatment decreased the exchangeable Zn but increased loose organic-, carbonate- and Fe-Mn oxides-bound Zn concentrations in soil without plants. The exchangeable, loose organic- and carbonate-bound Zn concentrations in soil with plants was increased by N0.2Zn10 and N0.4Zn10 treatment at different growth stages. Different rates of N combined with Zn application influenced the proportion of Zn in different fractions in soil with and without plants at different growth stages. At Zn10, N0.4 treatment showed higher yield, N and Zn concentrations in shoot and grain, and available Zn concentration in soil, but lower pH in soil than N0.2 treatment. In addition, soil without plants had higher available Zn concentrations and lower pH than did the soil with plants. There were significant differences in Zn chemical fractions concentrations and proportions between the soils with and without plants at each growth stage. Therefore, combined influence of roots and the combination of N and Zn (especially N0.4Zn10 treatment) improved the bio-availability of Zn in soil via changing the soil pH and promoting the transformation and distribution of Zn in different fractions.
Highlights
Zinc (Zn) is essential for human body and is involved in physiological and nutritional functions in human growth and development, including humoral and cellular immunity as well as the synthesis of proteins and nucleic acids (Bonaventuraa et al, 2015)
The aims of this study were: (i) to re-examine the effect of N combined with Zn application on Zn concentration in winter wheat; (ii) to investigate available Zn, pH, and Zn chemical fractions in soil influenced by the root system of winter wheat; and (iii) to investigate available Zn, pH, and Zn chemical fractions in soil in response to different N application rates, combined with Zn during pot trials
Our results suggested that the increased Zn concentration in shoots might be partially related to the enhanced growth that occurred following the application of N combined with Zn
Summary
Zinc (Zn) is essential for human body and is involved in physiological and nutritional functions in human growth and development, including humoral and cellular immunity as well as the synthesis of proteins and nucleic acids (Bonaventuraa et al, 2015). Zn deficiency results in a series of problems for humans, especially infants, such as loss of appetite and digestion, growth retardation, and brain and immune system dysfunction (Prasad, 2014). Zn deficiency in the body can be resolved by human intervention, including dietary diversification, nutritional supplements, food intensification and biofortification (Graham et al, 2001). For areas with severe zinc deficiency, such as sub-Saharan Africa and South Asia, food crops in those developing countries are the main source of Zn in the human body. Biofortification of grain crops with Zn by breeding and fertilization appears to be cost-effective and promising as an approach for improving Zn concentration in grain, thereby contributing to human health (Graham et al, 2001; Bouis et al, 2011; Velu et al, 2014)
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