Crop rotations under no-till (NT) have been a strategy to increase soil organic carbon (SOC) and mitigate greenhouse gas (GHG) emissions, enhancing the cropping system efficiency. However, there is still controversy on the role of grasses and legumes, and species diversity and their impacts. This study aimed to assess the GHG emissions, SOC, and Nitrogen (TN) in a soybean production system managed under NT in rotation with different species in the fall–winter and the spring seasons. Main plots during the fall–winter were (1) Triticale (x Triticosecale) and (2) Sunflower (Helianthus annuus). Subplots established in the spring were (a) Sunn hemp (Crotalaria juncea), (b) Sorghum (Sorghum bicolor), (c) Pearl millet (Pennisetum glaucum), plus a (d) Fallow treatment. Soybean was grown every year in the summer, in sub-subplots. The GHG emission was affected according to crop species. In the spring, Sunn hemp emitted more nitrous oxide (N2O) (0.82 kg ha−1) than fallow (0.58 kg ha−1); however, the high C and N inputs by the legume and also other cover crop residues reduced the relative emissions compared with fallow. Growing pearl millet or Sunn hemp as a spring cover crop increases SOC by 7% on average compared with fallow. The N2O emission of Sunn hemp accounted for only 0.28% of the total N accumulated in the legume residues, notably lower than IPCC estimates. In the fall–winter, Triticale increased SOC by 7%, decreased CO2 emission by 18%, and emitted 20% lower GHG to produce the same soybean yield compared with sunflower. Soybean rotation with triticale in fall–winter and Sunn hemp or pearl millet in spring decreases GHG emissions. Our results indicate that the right choice of species in rotation with soybean under NT increases SOC and may offset GHG emissions from tropical soils. It may be an important tool in mitigating potential global warming.

中文翻译：

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使用覆盖作物来抵消免耕热带土壤的温室气体排放

免耕 (NT) 下的作物轮作一直是增加土壤有机碳 (SOC) 和减少温室气体 (GHG) 排放、提高种植系统效率的一种策略。然而，关于草和豆类的作用、物种多样性及其影响仍然存在争议。本研究旨在评估在 NT 下管理的大豆生产系统中的温室气体排放量、SOC 和氮 (TN)，该系统在秋冬和春季与不同物种轮作。秋冬期间的主要地块是 (1) 黑小麦 (x 小麦鳞片) 和 (2) 向日葵 (向日葵）。春季建立的子地块是 (a) Sunn 麻 (猪笼草), (b) 高粱 (双色高粱), (c) 珍珠粟 (狼尾草)，加上 (d) 休耕处理。大豆每年在夏季种植，在子地块中。温室气体排放受到作物种类的影响。在春天，Sunn 大麻释放出更多的一氧化二氮（N2O) (0.82 公斤公顷-1) 比休耕 (0.58 kg ha-1); 然而，与休耕相比，豆科植物和其他覆盖作物残留物的高碳和氮投入减少了相对排放。与休耕相比，种植珍珠粟或 Sunn 大麻作为春季覆盖作物使 SOC 平均增加 7%。然后2Sunn 大麻的 O 排放仅占豆科植物残留物中累积的总 N 的 0.28%，明显低于 IPCC 的估计。在秋冬，小黑麦增加了 7% 的 SOC，减少了 CO2与向日葵相比，在大豆产量相同的情况下，排放量减少了 18%，温室气体排放量减少了 20%。秋冬季大豆轮作，春季轮作黑小麦，春季使用 Sunn 麻或珍珠粟，可减少温室气体排放。我们的结果表明，在 NT 下正确选择与大豆轮作的物种会增加 SOC，并可能抵消热带土壤的温室气体排放。它可能是缓解潜在全球变暖的重要工具。