Funding information USDepartment ofEnergy,Grant/Award Numbers:DE-SC0018409,DE-ACO576RL01830;National ScienceFoundation, Grant/AwardNumber:DEB 1027253 Abstract Expanding biofuel production is expected to accelerate the conversion of unmanaged marginal lands to meet biomass feedstock needs. Greenhouse gas production during conversion jeopardizes the ensuing climate benefits, but most research to date has focused only on conversion to annual crops and only following tillage. Here we report the global warming impact of converting USDA Conservation Reserve Program (CRP) grasslands to three types of bioenergy crops using no-till (NT) vs. conventional tillage (CT). We established replicated NT and CT plots in three CRP fields planted to continuous corn, switchgrass, or restored prairie. For the 2 yr following an initial soybean year in all fields, we found that, on average, NT conversion reduced nitrous oxide (N2O) emissions by 50% and CO2 emissions by 20% compared with CT conversion. Differences were higher in Year 1 than in Year 2 in the continuous corn field, and in the two perennial systems the differences disappeared after Year 1. In all fields net CO2 emissions (asmeasured by eddy covariance)were positive for the first 2 yr following CT establishment, but following NT establishment net CO2 emissions were close to zero or negative, indicating net C sequestration. Overall, NT improved the global warming impact of biofuel crop establishment following CRP conversion by over 20-fold compared with CT (−6.01 Mg CO2e ha−1 yr−1 for NT vs. −0.25 Mg CO2e ha−1 yr−1 for CT, on average). We also found that Intergovernmental Panel on Climate Change estimates of N2O emissions (as measured by static chambers) greatly underestimated actual emissions for converted fields regardless of tillage. Policies should encourage adoption of NT for converting marginal grasslands to perennial bioenergy crops to reduce C debt andmaximize climate benefits.

中文翻译：

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免耕种植提高了边缘草原生物能源作物的气候效益

资金信息 美国能源部，拨款/奖励编号：DE-SC0018409，DE-ACO576RL01830；国家科学基金会，拨款/奖励编号：DEB 1027253 摘要 预计扩大生物燃料生产将加速未管理边际土地的转化，以满足生物质原料需求。转化过程中产生的温室气体会危及随之而来的气候效益，但迄今为止的大多数研究都只关注转化为一年生作物，并且只关注耕作之后。在这里，我们报告了使用免耕 (NT) 与传统耕作 (CT) 将美国农业部保护保护区计划 (CRP) 草原转变为三种类型的生物能源作物对全球变暖的影响。我们在种植连续玉米、柳枝稷或恢复草原的三个 CRP 田中建立了重复的 NT 和 CT 地块。在所有田地的第一个大豆年之后的 2 年中，我们发现，与 CT 转换相比，NT 转换平均减少了 50% 的一氧化二氮 (N2O) 排放和 20% 的 CO2 排放。在连续玉米田中，第 1 年的差异高于第 2 年，在两个多年生系统中，第 1 年之后差异消失。在 CT 后的前 2 年，所有田地的净 CO2 排放量（通过涡度协方差测量）为正建立，但在 NT 建立之后，净 CO2 排放接近于零或为负，表明净 C 固存。总体而言，与 CT 相比，NT 将 CRP 转化后生物燃料作物种植对全球变暖的影响提高了 20 倍以上（NT 为-6.01 Mg CO2e ha-1 yr-1，CT 为-0.25 Mg CO2e ha-1 yr-1 ， 一般）。我们还发现，政府间气候变化专门委员会对 N2O 排放量的估计（通过静态室测量）大大低估了改建田地的实际排放量，而不管耕作情况如何。政策应鼓励采用 NT 将边缘草原转变为多年生生物能源作物，以减少碳债务并最大限度地提高气候效益。