Abstract Intensive management of agroecosystems has been widely indicated as major responsible for soil degradation, thus negatively impacting on relationships between agriculture and climate change. Conservation tillage (i.e. no-till and minimum tillage) has been recommended for enhancing soil organic carbon (SOC) and total nitrogen (STN) stocks while having a positive impact on food security, biodiversity, water quality and the environment. Nevertheless, positive responses were mainly reported in hot and semiarid climates, with rainfed crops and low N fertilization rates. Therefore, the main objective of this study was to test the adoption of conservation tillage in intensive maize cropping systems under temperate soil, with high N fertilization rate (> 200 kg N ha−1 yr−1) and organic matter input (i.e. manure distribution and high biomass return), and with permanent optimum water moisture due to irrigation. We conducted an 8-year field experiment on a maize (Zea mays L.) monoculture to assess: (i) the effect of no-till (NT) and minimum tillage (MT), on grain yield and biomass return as compared with conventional tillage (CT); (ii) how tillage systems affect the evolution of SOC and STN levels over time under these conditions; (iii) soil aggregation processes and mechanisms leading to SOC and STN changes in the long-term. Results showed that MT increased maize grain yield (+7 %) and total biomass (+10 %) compared with CT. Conversely, NT reduced maize grain and biomass production during the initial 5-year transition, but afterwards increased maize yield up to that of CT. At the end of the experiment, SOC sequestration was increased under NT and MT by 1.45 and 1.52 Mg C ha−1 yr−1 compared with CT, respectively. Also, STN accumulation was higher under NT and MT than under CT (+0.15 and +0.17 Mg N ha−1 yr−1, respectively). Most of such a SOC and STN increase was located into C- and N-rich macroaggregates. Within those macroaggregates (large macroaggregates, LM; small macroaggregates, sM), we found that C and N pools associated to mM accounted for between 41 and 65 % of total C and N content in NT and MT systems across the different soil layers, which is beneficial for long-term C and N stabilization in soils. Thus, introducing conservation tillage within intensive agricultural context devoted to maize monoculture as that of the Po Valley should be recommended to: (i) maintain (or even increase) maize yield, and (ii) enhance SOC and STN accumulation and stabilization.

中文翻译：

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保护性耕作能否在不降低集约灌溉农田产量的情况下增加土壤碳和氮的积累？八年玉米单一栽培的结果

摘要 农业生态系统的集约化管理已被广泛认为是造成土壤退化的主要原因，从而对农业与气候变化之间的关系产生负面影响。保护性耕作（即免耕和少耕）已被推荐用于提高土壤有机碳 (SOC) 和总氮 (STN) 储量，同时对粮食安全、生物多样性、水质和环境产生积极影响。然而，积极的反应主要是在炎热和半干旱气候、雨育作物和低氮肥施用率的情况下报告的。因此，本研究的主要目的是测试在温带土壤下采用高施氮量（> 200 kg N ha−1 yr−1）和有机质输入（即 粪便分配和高生物量回报），并且由于灌溉而具有永久的最佳水分。我们对玉米 (Zea mays L.) 单一栽培进行了为期 8 年的田间试验，以评估：(i) 与常规作物相比，免耕 (NT) 和最少耕作 (MT) 对谷物产量和生物量回报的影响耕作（CT）；(ii) 在这些条件下，耕作系统如何影响 SOC 和 STN 水平随时间的演变；(iii) 导致长期 SOC 和 STN 变化的土壤团聚过程和机制。结果表明，与 CT 相比，MT 增加了玉米籽粒产量 (+7%) 和总生物量 (+10%)。相反，NT 在最初的 5 年过渡期间减少了玉米谷物和生物量产量，但随后将玉米产量提高到 CT 的产量。在实验结束时，与 CT 相比，NT 和 MT 下的 SOC 封存分别增加了 1.45 和 1.52 Mg C ha-1 yr-1。此外，NT 和 MT 下的 STN 积累比 CT 下更高（分别为 +0.15 和 +0.17 Mg N ha-1 yr-1）。大多数此类 SOC 和 STN 增加位于富含 C 和 N 的大聚集体中。在这些大团聚体（大团聚体，LM；小团聚体，sM）中，我们发现与 mM 相关的 C 和 N 库占不同土壤层的 NT 和 MT 系统中总 C 和 N 含量的 41% 至 65%，这有利于土壤中 C 和 N 的长期稳定。因此，应建议在集中式农业环境中引入保护性耕作，如波谷的玉米单一栽培那样：(i) 保持（甚至增加）玉米产量，