Long-term sustainability of intensive cropping systems in tropical soils depends on strategies to reconcile grain output, cover crops to maximize biomass yield for soil mulching, and maintaining soil organic carbon (SOC). In this study, we evaluated spatiotemporal constraints underpinning the diversification from soybean ( (L.) Merr.) monoculture under conventional tillage (CT) or no-tillage (NT) and soybean in succession with maize ( L.) double cropping (NTS3) to the use of millet ( L., NTS1) and brachiaria ( (R.Germ. & Evrard) Crins, NTS2) in successions or millet, crotalaria ( Roth.), and maize+brachiaria in rotations in a 12-year field experiment in an Oxisol. We quantified total grain output, total biomass production, and SOC contents and stocks (0–40 cm depth). Over 12 years, cumulative grain output under the double cropping (NTS3) was 135.0 Mg ha, with soybean-maize proportions of 35–65 %. Thus, the successions NTS1 and NTS2 would reduce maize grain output relative to NTS3 (7.3 Mg ha year). Under the rotations, reduction in soybean and maize grain output relative to NTS3 was about 1.4 and 4.1 Mg ha year, respectively. Biomass production under NTS3 was 12.0 Mg ha year but reached 15.7 Mg ha year under the rotation including summer soybean (1st and 2nd years) and off-season crotalaria (1st year) or maize+brachiria (2nd year), and only brachiaria (3rd year). Under this rotation, changes in SOC stocks were +2.0 Mg ha year for the 0–40 cm depth layer, whereas under NTS3 it was +1.4 Mg ha year, relative to the native Cerrrado. For soybean monoculture under CT or NT changes in SOC were about −0.5 Mg ha year relative to the native Cerrado. Overall, despite the reduced total grain output, the rotation system proposed may be critical to reconcile sustainable food security, soil protection by mulching and SOC maintenance in agricultural Cerrado soils.

中文翻译：

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管理热带土壤可持续粮食生产系统的权衡


热带土壤集约化种植系统的长期可持续性取决于协调粮食产量、覆盖作物以最大限度地提高土壤覆盖生物量产量以及维持土壤有机碳 (SOC) 的策略。在本研究中，我们评估了传统耕作（CT）或免耕（NT）下大豆（（L.）Merr.）单一栽培以及玉米（L.）双季（NTS3）下大豆连续种植多样化的时空限制。在一项为期 12 年的田间试验中，连续使用小米 ( L., NTS1) 和臂形草 ( (R.Germ. & Evrard) Crins, NTS2) 或轮作小米、猪屎豆 ( Roth.) 和玉米+臂形草在 Oxisol 中。我们量化了粮食总产量、生物量总产量以及 SOC 含量和库存（0-40 厘米深度）。 12年来，双季（NTS3）粮食累计产量为135.0毫克公顷，大豆-玉米比例为35-65%。因此，相对于 NTS3（每年 7.3 毫克公顷），NTS1 和 NTS2 演替将减少玉米粮食产量。在轮作下，大豆和玉米产量相对于NTS3分别减少约1.4和4.1毫克公顷年。 NTS3下的生物量产量为每年12.0毫克公顷，但在包括夏季大豆（第一年和第二年）和淡季猪屎豆（第一年）或玉米+臂形草（第二年）和仅臂形草（第三年）的轮作下达到15.7毫克公顷年年）。在这种轮换下，0-40 厘米深度层的 SOC 储量变化为每年 +2.0 毫克公顷，而在 NTS3 下，相对于本地塞拉多，每年变化为 +1.4 毫克公顷。对于 CT 或 NT 下的大豆单一栽培，相对于本地塞拉多，SOC 变化约为每年 -0.5 毫克/公顷。 总体而言，尽管粮食总产量减少，但拟议的轮作制度对于协调可持续粮食安全、覆盖农业土壤保护和塞拉多农业土壤的有机碳维护可能至关重要。