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Impact of dissolved organic matter on Zn extractability and transfer in calcareous soil with maize straw amendment

Chen, Yanlong, Shi, Jianglan, Tian, Xiaohong, Jia, Zhou, Wang, Shaoxia, Chen, Juan, Zhu, Wenling
Journal of soils and sediments 2019 v.19 no.2 pp. 774-784
arable soils, calcareous soils, corn straw, dissolved organic matter, zinc, zinc sulfate, China
PURPOSE: Crop straw return into arable land is a common method of disposing of excess straw in China and can improve soil dissolved organic matter (DOM) that is known to modify soil zinc (Zn) extractability and mobility. MATERIALS AND METHODS: We conducted a soil box (internal dimensions, 160 × 140 × 80 mm³) experiment to evaluate the response of Zn extractability and transfer by diffusion to DOM after maize straw amendment (St, 0 and 15 g kg⁻¹) in calcareous soil treated with ZnSO₄·7H₂O (Zn, 0 and 20 mg kg⁻¹). Soil treated with St₀Zn₀ (control), St₁₅Zn₀, St₀Zn₂₀, or St₁₅Zn₂₀ was isolated in the 10-mm center of the box, and untreated soil was placed in compartments at either side. RESULTS AND DISCUSSION: Results revealed that addition of St₀Zn₂₀ or St₁₅Zn₂₀ increased the concentration of Zn extracted with diethylenetriaminepentaacetic acid (DTPA-extractable Zn) in the central layer compared with control or addition of St₁₅Zn₀. Over the course of 45 days, transfer of DTPA-extractable Zn into the adjacent untreated soil was detected at 15–20 mm in soil with St₁₅Zn₂₀ but at 10–15 mm with St₀Zn₂₀ and only 0–5 mm with St₁₅Zn₀. Additionally, a higher amount of DTPA-extractable Zn transfer into the adjacent untreated soil also occurred in St₁₅Zn₂₀. This increased DTPA-extractable Zn transfer may be associated with the formation of Zn-fulvic acid complexes with the provision of DOM derived from straw. CONCLUSIONS: Soluble Zn combined with straw return may be a promising strategy for improving both Zn mobility and extractability in calcareous soil.