Cover cropping is a practice with potential to reduce post-harvest surplus of soil nitrate (NO₃^-), a mobile form of nitrogen naturally susceptible to losses. Increased soil NO₃^- leaching occurs when high soil NO₃^- coincides with high drainage events – a common occurrence during the non-growing season in cold and humid climates. The potential of cover crops to reduce NO₃^- leaching can be affected by the performance of the cover crop and by edaphic-climatic conditions (e.g., freeze-thaw cycles, soil type) and is subjected to interannual variation. Here, we evaluate soil type and crop rotation effects on soil parameters (i.e., NO₃^- concentration, temperature, water content) and on NO₃^- leaching under freeze-thaw conditions, using a high-frequency weighing lysimeter system. The soil type consisted of silt loam (SIL) and loamy sand (LS) soils and the crop rotation consisted of a rotation with a mixture of leguminous/non-leguminous cover crops (+CC) and no cover crop (-CC). This research was conducted during periods of 2017/2018 and 2018/2019 subjected to significant drainage. Our results indicated that cover crops did not affect drainage but affected soil temperature, with warmer soils observed over the winter when cover crops were used (+CC) than without cover-crops (-CC). Moreover, the cereal-crucifer-legume mixture after spring wheat reduced soil NO₃^- content by 80% compared to -CC during 2017/2018. For 2018/2019, due to poor establishment of the cereal-legume mixture under-seeded to corn, no reduction in soil NO₃^- content was observed. The reduction in soil NO₃^- in +CC plots for 2017/2018 translated to a significant reduction (by 67%) in NO₃^- leaching averaged across soil types. Soil drainage, NO₃^- content and NO₃^- leaching were not affected by soil type, an effect in part influenced by the boundary controls of the lysimeter system which mimicked soil conditions of a non-LS adjacent/reference field. To expand our results, we estimated the potential drainage of a hypothetical excessively drained LS (ED-LS) – a soil naturally subjected to high hydraulic conductivity and low water holding capacity. Overall, our results indicated that cover cropping can reduce NO₃^- leaching independent of soil type but the effect can be pronounced for ED-LS.

覆盖作物是一种有可能减少收获后土壤硝酸盐 (NO ₃ ^- )过剩的做法，硝酸盐是一种自然易受损失的移动形式的氮。增加土壤NO ₃ ^-浸出时出现高土壤NO ₃ ^-高排放事件一致-在寒冷和潮湿的气候非生长季节经常发生的。覆盖作物减少 NO ₃ ^-浸出的潜力会受到覆盖作物的性能和土壤气候条件（例如，冻融循环、土壤类型）的影响，并且会受到年际变化的影响。在这里，我们评估土壤类型和作物轮作对土壤参数（即 NO ₃ ^-浓度、温度、水含量）和 NO ₃ ^-在冻融条件下浸出，使用高频称重蒸渗仪系统。土壤类型由粉壤土 (SIL) 和壤土 (LS) 土壤组成，轮作由豆科/非豆科覆盖作物 (+CC) 和无覆盖作物 (-CC) 的混合轮作组成。这项研究是在 2017/2018 和 2018/2019 期间进行的，排水量很大。我们的结果表明，覆盖作物不会影响排水，但会影响土壤温度，在冬季使用覆盖作物 (+CC) 时观察到的土壤比不使用覆盖作物 (-CC) 时更温暖。此外，春小麦后的谷物-十字花科植物-豆类混合物减少了土壤 NO ₃ ^-与 2017/2018 年的 -CC 相比，含量增加了 80%。对于 2018/2019 年，由于谷物-豆类混合物在玉米中的建立不良，未观察到土壤 NO ₃ ^-含量降低。2017/2018 年 +CC 地块中土壤 NO ₃ ^-的减少转化为 NO ₃ ^-平均浸出量显着减少（67%）。土壤排水、NO ₃ ^-含量和NO ₃ ^-浸出不受土壤类型的影响，该影响部分受模拟非 LS 相邻/参考田地土壤条件的蒸渗仪系统边界控制的影响。为了扩大我们的结果，我们估计了一个假设的过度排水 LS (ED-LS) 的潜在排水量 - 一种自然受到高导水率和低保水能力的土壤。总的来说，我们的结果表明，覆盖作物可以减少 NO ₃ ^-浸出，与土壤类型无关，但对 ED-LS 的影响可能很明显。