Agricultural systems of the Argentinean Pampas generally use rotations of summer crops under no-tillage and apply fertilization at rates that do not compensate nutrient exports with grain harvest, resulting in negative balances and soil fertility loss. However, the humid climate, long fallow periods and soil factors enhance nitrogen (N) and phosphorus (P) leaching, which has a negative impact on freshwater ecosystems. We propose to evaluate the effect of soil type and replacement of fallow periods with cover crops on drainage and N and P leaching. We used lysimeters containing two Mollisols of contrasting texture and porosity (a Typic Argiudoll and a Typic Hapludoll), and cultivated between 2014 and 2022 with a maize-soybean rotation with (M-CC-S) and without (M-S) cover crops under no tillage.

The amount of drainage varied with rainfall (p<0.01), was similar between soils and higher in M-S than in M-CC-S during the intercropping period (148 vs 96 mm, p<0.05). The correlation between daily rainfall and drainage was higher for the Typic Argiudoll (r=0.46 and 0.42, for M-S and M-CC-S, respectively) than for the Typic Hapludoll (0.28 and 0.23 for M-S and M-CC-S, respectively) when considering same-day events, and it decreased for the Typic Argiudoll (r=0.31 and 0.26, for the M-S and M-CC-S, respectively) but not for the Typic Hapludoll (0.28 and 0.21 for the M-S and M-CC-S, respectively) with a 1-day lag between series. The amount of N and P lost through leaching varied with drainage (p<0.01). Cover crops reduced nitrate leaching to a greater extent in the Typic Hapludoll (from 30.4 to 3.3 kg ha⁻¹ period⁻¹) than in the Typic Argiudoll (from 17.6 to 2.0 kg ha⁻¹ period⁻¹) (p<0.05). Soil type modified P leaching in M-S (0.32 and 0.11 kg ha⁻¹ period⁻¹ for the Typic Argiudoll and the Typic Hapludoll, respectively) and M-CC-S had intermediate P leaching (0.17 and 0.16 kg P ha⁻¹ period⁻¹ for the Argiudoll and Hapludoll, respectively) (p<0.05).

We conclude that: 1) water flows through different channels in each soil, the rapid flow of the Typic Argiudoll probably occurs through preferential flow channels (macropores) while the slower flow of the Typic Hapludoll is probably associated to matrix porosity, 2) P leaching is related to soil type (Typic Argiudoll > Typic Hapludoll) and drainage reduction by cover crops off-sets P leaching through macropores in the Typic Argiudoll, and 3) cover crops reduce N leaching, due to drainage reduction and N retention in cover crop biomass.

阿根廷潘帕斯草原的农业系统通常在免耕条件下采用夏季作物轮作，施肥量不能通过谷物收获来补偿养分输出，导致负平衡和土壤肥力丧失。然而，潮湿的气候、漫长的休耕期和土壤因素加剧了氮（N）和磷（P）的淋溶，这对淡水生态系统产生负面影响。我们建议评估土壤类型和用覆盖作物替代休耕期对排水和氮磷淋失的影响。我们使用含有两种具有对比质地和孔隙度的 Mollisols （一种典型的 Argiudoll和一种典型的 Hapludoll）的蒸渗仪，并在 2014 年至 2022 年间进行玉米-大豆轮作种植，其中有（M-CC-S）和无（MS）覆盖作物，无覆盖作物。耕作。

排水量随降雨量的变化而变化（p<0.01），在间作期间，土壤之间的排水量相似，并且 MS 的排水量高于 M-CC-S 的排水量（148 毫米 vs 96 毫米，p<0.05）。典型 Argiudoll 的日降雨量和排水量之间的相关性（对于 MS 和 M-CC-S，r 分别为 0.46 和 0.42）高于典型 Hapludoll（对于 MS 和 M-CC-S，分别为 0.28 和 0.23） ）在考虑当天事件时，典型 Argiudoll 的下降（对于 MS 和 M-CC-S，r 分别为 0.31 和 0.26），但对于典型 Hapludoll 则没有下降（对于 MS 和 M-r 分别为 0.28 和 0.21） CC-S），系列之间有 1 天的滞后。淋滤损失的 N 和 P 量随排水量的变化而变化 (p<0.01)。^{与典型的Argiudoll（从17.6至2.0 kg ha -1} period ^-1）相比，典型Hapludoll（从30.4至3.3 kg ha ^-1 period ^{-1 ）}覆盖作物更大程度地减少硝酸盐淋溶（p<0.05）。MS 中土壤类型改良的 P 淋滤（典型 Argiudoll 和典型 Hapludoll 分别为0.32 和 0.11 kg ha ^-1 period ^{-1 ）和 M-CC-S 具有中间 P 淋滤（0.17 和 0.16 kg P ha -1} period ^-1） Argiudoll 和 Hapludoll 分别为^{1 ）（p<0.05）。}

我们的结论是：1）水流经每种土壤的不同通道，典型 Argiudoll 的快速流动可能通过优先流动通道（大孔）发生，而典型 Hapludoll 的较慢流动可能与基质孔隙度有关，2）P 淋滤与土壤类型（典型 Argiudoll > 典型 Hapludoll）和覆盖作物排水减少有关，通过典型 Argiudoll 中的大孔抵消 P 淋滤，3）覆盖作物减少 N 淋滤，因为排水减少和覆盖作物生物量中的 N 保留。