Effect of Straw Amendment on Soil Zn Availability and Ageing of Exogenous Water-Soluble Zn Applied to Calcareous Soil.

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

Monthly mean air temperature and accumulated rainfall during the incubation period.

<p>Monthly mean air temperature and accumulated rainfall during the incubation period.</p

Monthly mean air temperature and accumulated rainfall during the incubation period.

<p>Monthly mean air temperature and accumulated rainfall during the incubation period.</p

The parameters of diffusion equation in soils with the water-soluble Zn application (Zn) and along with straw (Straw+Zn) at the periods of 120–165 and 180–210 days.

<p>The parameters of diffusion equation in soils with the water-soluble Zn application (Zn) and along with straw (Straw+Zn) at the periods of 120–165 and 180–210 days.</p

The relative amount of ineffective Zn (<i>Zn</i>_<i>RI</i>) in soils with the water-soluble Zn application (Zn) alone and along with straw (Straw+Zn) at the various incubation periods.

<p>The bars on the curves are standard errors (<i>n</i> = 3) and the bars above the curves represent the least significant difference (<i>LSD</i>) at 5%.</p

Zn concentration among the fractions in soils with exogenous Zn and straw applications.

<p><b>Soil total Zn was separated into the Zn in exchangeable (EXCH, a), organic matter with low bonding forces (LOM, b), carbonate (CARB, c), manganese oxide (MNO, d), organic matter with high bonding forces (HOM, e), and residual (RES, f) fractions by a sequential extraction procedure</b>. The bars on the curves are standard errors (<i>n</i> = 3) and the bars above the curves represent the least significant difference (LSD) at 5% and "NS" means no significant difference.</p

Ageing rate of water-soluble Zn in soils with the Zn application (Zn) and along with straw (Straw+Zn).

<p>Ageing rate of water-soluble Zn in soils with the Zn application (Zn) and along with straw (Straw+Zn).</p

Summary of two-way ANOVAs for the effects of straw, Zn application and their interaction on soil DTPA-Zn, pH, and labile organic carbon (LOC) at the various incubation periods.

<p>Summary of two-way ANOVAs for the effects of straw, Zn application and their interaction on soil DTPA-Zn, pH, and labile organic carbon (LOC) at the various incubation periods.</p