Nitrate is a major groundwater inorganic contaminant that is mainly due to fertilizer leaching. Compost amendment can increase soils’ organic substances and thus promote denitrification in intensively cultivated soils. In this study, two agricultural plots located in the Padana plain (Ferrara, Italy) were monitored and modeled for a period of 2.7 years. One plot was initially amended with 30 t/ha of compost, not tilled, and amended with standard fertilization practices, while the other one was run with standard fertilization and tillage practices. Monitoring was performed continuously via soil water probes (matric potential) and discontinuously via auger core profiles (major nitrogen species) before and after each cropping season. A HYDRUS-1D numerical model was calibrated and validated versus observed matric potential and nitrate, ammonium, and bromide (used as tracers). Model performance was judged satisfactory and the results provided insights on water and nitrogen balances for the two different agricultural practices tested here. While water balance and retention time in the vadose zone were similar in the two plots, nitrate leaching was less pronounced in the plot amended with compost due to a higher denitrification rate. This study provides clear evidence that compost addition and no-tillage (conservation agriculture) can diminish nitrate leaching to groundwater, with respect to standard agricultural practices.

中文翻译：

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模拟传统和保护性农业种植系统中土壤硝酸盐的积累和浸出

硝酸盐是一种主要的地下水无机污染物，主要是由于肥料浸出。堆肥改良剂可以增加土壤的有机物质，从而促进集约化土壤中的反硝化作用。在这项研究中，位于帕达纳平原（意大利费拉拉）的两个农业地块被监测并模拟了 2.7 年的时间。一个地块最初使用 30 吨/公顷的堆肥进行了修正，未耕种，并采用标准施肥做法进行修正，而另一块地则采用标准施肥和耕作做法进行修正。在每个作物季节之前和之后，通过土壤水探针（基质势）连续进行监测，并通过螺旋钻核心剖面（主要氮种类）不连续地进行监测。对 HYDRUS-1D 数值模型进行校准和验证，对比观察到的基质势和硝酸盐、铵、和溴化物（用作示踪剂）。模型性能被认为是令人满意的，结果提供了对这里测试的两种不同农业实践的水和氮平衡的见解。虽然两个地块中渗流带的水平衡和停留时间相似，但由于更高的反硝化率，在用堆肥修正的地块中硝酸盐浸出不太明显。这项研究提供了明确的证据，表明添加堆肥和免耕（保护性农业）可以减少硝酸盐浸出到地下水中，这与标准农业实践有关。虽然两个地块中渗流带的水平衡和停留时间相似，但由于更高的反硝化率，在用堆肥修正的地块中硝酸盐浸出不太明显。这项研究提供了明确的证据，表明添加堆肥和免耕（保护性农业）可以减少硝酸盐浸出到地下水中，这与标准农业实践有关。虽然两个地块中渗流带的水平衡和停留时间相似，但由于更高的反硝化率，在用堆肥修正的地块中硝酸盐浸出不太明显。这项研究提供了明确的证据，表明添加堆肥和免耕（保护性农业）可以减少硝酸盐浸出到地下水中，这与标准农业实践有关。