In the Argentinean Humid Pampas, intensification practices like crop rotation, cover crops (CC), and fertilization can improve soil N balance. This study aimed to assess how intensification practices affect soil organic N (Norg), Norg in the particulate fraction (PF-Norg), and N mineralized during a short-term (7 d) anaerobic incubation (aN) in a 4-yr experiment with soybean [Glycine max (L.) Merr.]-based crop sequences. At two sites differing in initial soil organic matter (SOM), five crop sequences were evaluated: continuous soybean (Sb); continuous soybean fertilized with P and sulfur (S; Sbf); CC/PS-fertilized soybean (Sbf/CC); N-fertilized CC/PS-fertilized soybean (Sbf/CCf); NPS-fertilized crop rotation (Rot). In addition, at one site we evaluated the C and N accumulation in CC dry matter, CC inclusion effect on soil inorganic N dynamics, and C and N content in soybean grain and shoots. At Site 1 (low SOM), Norg and PF-Norg increased in intensified sequences as compared with Sb and Sbf, whereas no differences among treatments were detected at Site 2 (high SOM). Also, an increase in aN was observed in intensified treatments at both sites. At Site 2, soil sampling took place at soybean sowing and harvest during two growing seasons. At soybean sowing, Sb and Sbf presented ∼30 kg NO₃⁻–N ha⁻¹ more than intensified sequences, whereas at soybean harvest this trend was the opposite. In the fallow, CC captured N, minimizing N leaching without affecting N accumulation in soybean. Our results indicate that intensification in soybean-based sequences improves soil N balances.

中文翻译：

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农业的可持续集约化改善了阿根廷潮湿潘帕斯草原的土壤氮

在阿根廷潮湿的潘帕斯草原，轮作、覆盖作物 (CC) 和施肥等集约化措施可以改善土壤氮平衡。本研究旨在评估集约化做法如何影响土壤有机 N (Norg)、颗粒部分中的 Norg (PF-Norg) 和在 4 年实验中的短期（7 天）厌氧培养 (aN) 期间矿化的 N与大豆 [ Glycine max(L.) Merr.] 基于作物序列。在初始土壤有机质 (SOM) 不同的两个地点，评估了五种作物序列：连续大豆 (Sb)；连续施磷和硫磺（S；Sbf）的大豆；CC/PS 施肥大豆（Sbf/CC）；N施肥CC/PS施肥大豆（Sbf/CCf）；NPS施肥的轮作（Rot）。此外，在一个地点，我们评估了 CC 干物质中的 C 和 N 积累、CC 包含对土壤无机 N 动态的影响以及大豆籽粒和芽中的 C 和 N 含量。在站点 1（低 SOM），与 Sb 和 Sbf 相比，Norg 和 PF-Norg 在强化序列中增加，而在站点 2（高 SOM）未检测到处理之间的差异。此外，在两个部位的强化处理中都观察到了 aN 的增加。在站点 2，在两个生长季节的大豆播种和收获时进行土壤采样。在大豆播种时，Sb 和 Sbf 呈现 ∼30 kg NO₃ ^- -N ha ^-1比强化序列多，而在大豆收获时，这一趋势是相反的。在休耕期间，CC 捕获 N，最大限度地减少 N 浸出而不影响大豆中的 N 积累。我们的结果表明，基于大豆的序列集约化改善了土壤氮平衡。