J Environ Qual. 2019 Jan;48(1):127-135. doi: 10.2134/jeq2018.08.0308.
The effectiveness of gypsum in reducing runoff P losses from soils and the mechanisms responsible are well documented; however, gypsum amendment effects in reducing redox-induced P losses from flooded soils are less researched and documented. We examined the effect of gypsum amendment on P release from freshly manured soils to pore water and floodwater with continuous flooding for 56 d in the laboratory. Three soils (Pembina, Denham, and Dencross series) collected from Manitoba, Canada, were preincubated with liquid swine manure. Each preincubated manured soil was packed into vessels with or without recycled wallboard gypsum in triplicates and flooded for 56 d, during which pore water and floodwater were sampled weekly and analyzed for pH and dissolved reactive P (DRP), Ca, Mg, Fe, and Mn concentrations. Change in soil redox potential (Eh) with flooding was also monitored. Wallboard gypsum amendment significantly decreased the pore water and surface floodwater DRP concentrations in all three soils for most days after flooding (DAF). The Dencross soil, which had Olsen P about fivefold greater than the other soils, showed the greatest magnitude decrease in DRP concentration with gypsum amendment, by 1.27 mg L on 49 DAF and 0.99 mg L on 21 DAF for pore water and floodwater, respectively. Gypsum amendment (i) delayed the Eh reduction with flooding beyond +200 mV, (ii) decreased pore water pH, and (iii) increased concentrations of Ca, Mg, and Mn in pore water favoring precipitation of P, all of which may have directly or indirectly reduced the P release from flooded soils to overlying floodwater.
石膏降低土壤径流磷流失的有效性及其相关机制已有充分的文献记载；然而，石膏改良剂在减少淹没土壤中氧化还原诱导的磷流失方面的效果研究和文献记载较少。我们在实验室中用连续淹水 56 天的方法，研究了石膏改良剂对新鲜施肥土壤向孔隙水和洪水释放磷的影响。从加拿大马尼托巴省采集了 Pembina、Denham 和 Dencross 三个系列的土壤，这些土壤与液态猪粪一起进行预孵育。每个预孵育的施肥土壤分为三组，一组在容器中加入再生墙板石膏，一组不加，每组重复三次，然后进行 56 天的淹水，在此期间每周采集孔隙水和洪水样，分析 pH 值和溶解反应磷（DRP）、Ca、Mg、Fe 和 Mn 浓度。还监测了淹水过程中土壤氧化还原电位（Eh）的变化。墙板石膏改良剂显著降低了所有三种土壤在淹水后的大多数日子（DAF）的孔隙水和地表洪水 DRP 浓度。与其他土壤相比，Olsen P 约高出五倍的 Dencross 土壤，在石膏改良剂的作用下，DRP 浓度的降幅最大，分别在 49 和 21 DAF 时，孔隙水和洪水的降幅分别为 1.27 和 0.99 mg/L。石膏改良剂（i）延迟了 Eh 随淹水的降低，使其保持在+200 mV 以上，（ii）降低了孔隙水的 pH 值，（iii）增加了孔隙水中 Ca、Mg 和 Mn 的浓度，有利于磷的沉淀，所有这些都可能直接或间接地减少了从淹没土壤向覆盖洪水的磷释放。
