Abstract
Organic matter plays a key role in availability and transformation of soil Zn (zinc), which greatly controls Zn concentrations in cereal grains and human Zn nutrition level. Accordingly, soils homogenized with the wheat straw (0, 12 g straw kg-1) and Zn fertilizer (0, 7 mg Zn kg-1) were buried and incubated in the field over 210 days to explore the response of soil Zn availability and the ageing of exogenous Zn to straw addition. Results indicated that adding straw alone scarcely affected soil DTPA-Zn concentration and Zn fractions because of the low Zn concentration of wheat straw and the high soil pH, and large clay and calcium carbonate contents. However, adding exogenous Zn plus straw increased the DTPA-Zn abundance by about 5-fold and had the similar results to adding exogenous Zn alone, corresponding to the increased Zn fraction loosely bounded to organic matter, which had a more dominant presence in Zn reaction than soil other constituents such as carbonate and minerals in calcareous soil. The higher relative amount of ineffective Zn (~50%) after water soluble Zn addition also occurred, and at the days of 120–165 and 180–210when the natural temperature and rainfall changed mildly, the ageing process of exogenous Zn over time was well evaluated by the diffusion equation, respectively. Consequently, combining crop residues with exogenous water soluble Zn application is promising strategy to maximize the availability of Zn in calcareous soil, but the higher ageing rate of Zn caused by the higher Zn mobility should be considered.
Highlights
Recent estimates have suggested that ~50% of the global population is at risk of Zn deficiency
A 2% increase in the mean diethylene triaminepentacetate acid (DTPA)-Zn concentration only was recorded for the straw application
The values of soil DTPA-Zn had a mild fluctuation with time in the absence of Zn treatments (Table 2)
Summary
Recent estimates have suggested that ~50% of the global population is at risk of Zn deficiency. Zn Availability and Ageing of Exogenous Zn in Calcareous Soil practice that is used globally to improve Zn availability in soil [3, 4]. Research has shown that the effects of Zn fertilizer on plant Zn concentrations are limited in calcareous soil [5]. Such limited effects might be mainly attributed to the poor diffusion of free Zn to plant roots, which was minimized by the variety of physical and chemical constraints (e.g., high pH and large carbonate and clay contents) [6]. Water-soluble Zn fertilizer becomes slowly but steadily more stable and immobile over time [7], a process known as ageing, which leads to a decrease in Zn solubility, mobilization and Zn fertilizer efficiency
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