Global warming can intensify the soil organic matter (SOM) turnover, damaging soil health. Crop residues left on the soil are important to maintain a positive SOM budget and nutrient cycling. But, sugarcane (Saccharum officinarum) straw has been removed from the field for bioenergy purposes. We hypothesize that global warming, together with straw removal, will negatively impact Brazil’s ethanol carbon footprint. Thus, we conducted an experiment under controlled conditions to evaluate the impacts of warming and straw removal on greenhouse gas (GHG) emissions, soil carbon and nitrogen storage, and nutrient cycling. Two soils (Rhodic Acrisol and Eutric Nitisol) were tested with three rates of sugarcane straw removal (no removal (NR): equivalent to 12 Mg ha⁻¹; medium removal (MR): 6 Mg ha⁻¹; and total removal (TR): bare soil) and submitted to two temperatures (24 °C and 30 °C) and soil moistures (30% and 50%). Straw decomposition was stimulated by lower rates of straw removal, resulting in increases on carbon dioxide (CO₂) emissions between 5 to 14 times, and N₂O between 25 and 40%. There were no significant methane (CH₄) fluxes. Soil carbon and nitrogen did not change due to straw removal, yet labile carbon fractions (living and non-living) were highly impacted, causing reductions of 15 to 40% on the carbon management index (CMI). Furthermore, straw removal reduced nutrient cycling between 10 and 30%. Overall, in a scenario of warming, our findings point to an intensification of SOM dynamic, resulting in increases of 35% on the GHG emissions and a CMI reduction by 20%. In practical terms, at least 6 Mg ha⁻¹ of straw should be left in the field, guaranteeing raw-material for bioenergy, without causing major impacts on the GHG emission and soil attributes.

中文翻译：

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甘蔗秸秆生物能源管理：全球变暖对温室气体排放和土壤碳存储的影响

全球变暖会加剧土壤有机质（SOM）的转化，从而损害土壤健康。残留在土壤上的作物残渣对于维持正的SOM预算和养分循环很重要。但是，出于生物能源目的，已经从田野中去除了甘蔗（Saccharum officinarum）秸秆。我们假设全球变暖加上秸秆清除将对巴西的乙醇碳足迹产生负面影响。因此，我们在受控条件下进行了一项实验，以评估变暖和除草对温室气体（GHG）排放，土壤碳氮存储和养分循环的影响。测试了两种土壤（Rhodic Acrisol和Eutric Nitisol）的甘蔗秸秆去除率（无去除率（NR）：相当于12 Mg ha ^-1；中等去除率（MR）：6 Mg ha）的三种速率^-1 ; 总清除量（TR）：裸露的土壤），并接受两个温度（24°C和30°C）和土壤湿度（30％和50％）。较低的秸秆去除率可促进秸秆分解，从而使二氧化碳（CO ₂）排放增加5至14倍，而N ₂ O则增加25至40％。没有明显的甲烷（CH ₄）助焊剂。由于除去秸秆，土壤碳和氮没有变化，但不稳定的碳组分（活性和非活性）受到很大影响，导致碳管理指数（CMI）降低了15％至40％。此外，除草还减少了10％至30％的养分循环。总体而言，在变暖的情况下，我们的发现表明SOM动态加剧，导致温室气体排放增加了35％，CMI减少了20％。实际上，应在田间至少留出6 Mg ha ^-1的稻草，以保证生物能源的原料，而不会对温室气体排放和土壤特性造成重大影响。