Department of Soil Science, "Luiz de Queiroz" College of Agriculture - University of São Paulo, Avenida Pádua Dias, 11, Piracicaba, SP, 13418-260, Brazil; Department of Soil and Crop Sciences, Colorado State University, Fort Collins, CO, 80521, USA.
Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO, 80521, USA.
J Environ Manage. 2023 Dec 1;347:119149. doi: 10.1016/j.jenvman.2023.119149. Epub 2023 Sep 30.
The recent agricultural expansion in the Matopiba region, Brazil's new agricultural frontier, has raised questions about the risk of increasing soil organic carbon (SOC) loss as large areas of native vegetation (NV; i.e., Cerrado biome) have been replaced by large-scale mechanized agriculture. Although sustainable managements, such as integrated crop-livestock (ICL) systems, are considered strategic to counterbalance the SOC loss associated with land-use change (LUC) while keeping food production, little is known about their long-term effects on SOC stocks in the Matopiba region. To this end, we used the DayCent model to simulate the effects of converting the management commonly used in this region, i.e., soybean-cotton rotation under no-tillage (NT), into ICL systems with distinct levels of intensification (e.g., crop rotations: soybean-pasture and soybean-pasture-cotton; soil and crop management: grass irrigation, scarification/harrowing, and length of grass cultivation) on long term SOC dynamics. Additionally, data from two projected climate scenarios: SSP2-4.5 [greenhouse gases emissions (GHG) will not change markedly over time and global temperature will increase by 2.0 °C by 2060] and SSP5-8.5 (marked changes in GHG emissions are expected to occur resulting in an increase of 2.4 and 4.4 °C in global temperature in the middle and at the end of the century) were included in our simulations to evaluate climate change effects on SOC dynamics in this region. Based on a 50-yr-time frame simulation, we observed that SOC stocks under ICL systems were, on average, 23% and 47% higher than in the NV (36.9 Mg ha) and soybean-cotton rotation under NT (30.9 Mg ha), respectively. Growing grasses interlaid with crops was crucial to increase SOC stocks even when disruptive soil practices were followed. Although the irrigation of grass resulted in an early increase of SOC stocks and a higher pasture stoking rate, it did not increase SOC stocks in the long term compared to non-irrigated treatments. The SSP2-4.5 and SSP5-8.5 climate scenarios had little effects on SOC dynamics in the simulated ICL systems. However, additional SOC loss (∼0.065 Mg ha yr) is predicted to occur if the current management is not improved. These findings can help guide management decisions for the Matopiba region, Brazil, to alleviate the anthropogenic pressure associated with agriculture development. More broadly, they confirm that crop-livestock integration in croplands is a successful strategy to regenerate SOC.
巴西新农业前沿地带马托皮巴地区（Matopiba region）最近的农业扩张引发了人们对土壤有机碳（SOC）损失风险的关注，因为大面积的原生植被（即塞拉多生物群落）已被大规模机械化农业所取代。尽管综合作物-牲畜（ICL）系统等可持续管理方法被认为是在保持粮食生产的同时，抵消与土地利用变化（LUC）相关的 SOC 损失的战略，但对于它们在马托皮巴地区长期对 SOC 储量的影响知之甚少。为此，我们使用 DayCent 模型来模拟在该地区常用的管理方式（即免耕下的大豆-棉花轮作（NT））转变为具有不同集约化水平的 ICL 系统（例如，作物轮作：大豆-牧场和大豆-牧场-棉花；土壤和作物管理：草地灌溉、耙地/耕地和草地耕作长度）对长期 SOC 动态的影响。此外，我们还将两个预测的气候情景的数据（SSP2-4.5[温室气体排放（GHG）不会随时间显著变化，全球温度到 2060 年将升高 2.0°C]和 SSP5-8.5[预计 GHG 排放将发生显著变化，导致全球温度在本世纪中叶和末期分别升高 2.4°C 和 4.4°C]）纳入我们的模拟中，以评估气候变化对该地区 SOC 动态的影响。基于 50 年的时间框架模拟，我们观察到，在 ICL 系统下，SOC 储量平均比原生植被（36.9 Mg ha）和免耕下的大豆-棉花轮作（30.9 Mg ha）分别高出 23%和 47%。即使采用破坏性土壤措施，在作物间种植草地对增加 SOC 储量也至关重要。尽管草地灌溉导致 SOC 储量的早期增加和更高的牧场蓄碳率，但与非灌溉处理相比，它并没有在长期内增加 SOC 储量。SSP2-4.5 和 SSP5-8.5 气候情景对模拟的 ICL 系统中的 SOC 动态几乎没有影响。然而，如果不改进当前的管理，预计还会有额外的 SOC 损失（约 0.065 Mg ha yr）。这些发现可以帮助指导巴西马托皮巴地区的管理决策，以减轻与农业发展相关的人为压力。更广泛地说，它们证实了在耕地中进行作物-牲畜一体化是一种成功的策略，可以使 SOC 再生。
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