Department of Soil and Crop Sciences, Colorado State University, Fort Collins, Colorado, USA.
Natural Resources Ecology Laboratory, Colorado State University, Fort Collins, Colorado, USA.
Glob Chang Biol. 2024 Nov;30(11):e17591. doi: 10.1111/gcb.17591.
Breeding annual crops for enhanced root depth and biomass is considered a promising intervention to accrue soil organic carbon (SOC) in croplands, with benefits for climate change mitigation and soil health. In annual crops, genetic technology (seed) is replaced every year as part of a farmer's fixed costs, making breeding solutions to climate change more scalable and affordable than management approaches. However, mechanistic understanding and quantitative estimates of SOC accrual potentials from crops with enhanced root phenotypes are lacking. Maize is the highest acreage and yielding crop in the US, characterized by relatively low root biomass confined to the topsoil, making it a suitable candidate for improvement that could be rapidly scaled. We ran a 2-year field experiment to quantify the formation and composition (i.e., particulate (POM), coarse and fine mineral-associated organic matter (chaOM and MAOM, respectively) of new SOC to a depth of 90 cm from the decomposition of isotopically labeled maize roots and exudates. Additionally, we used the process-based MEMS 2 model to simulate the SOC accrual potential of maize root ideotypes enhanced to either shift root production to deeper depths or increase root biomass allocation, assuming no change in overall productivity. In our field experiment, maize root decomposition preferentially formed POM, with doubled efficiency below 50 cm, while root exudates preferentially formed MAOM. Modeling showed that shifting root inputs to deeper layer or increasing allocation to roots resulted in a deterministic increase in SOC, ranging from 0.05 to 0.15 Mg C ha per year, which are at the low end of the range of published SOC per hectare annual accrual estimates from adoption of a variety of crop management practices. Our analysis indicates that for maize, breeding for increasing root inputs as a strategy for SOC accrual has limited impact on a per-hectare basis, although given that globally maize is produced on hundreds of millions of hectares each year, there is potential for this technology and its effect to scale. For maize-soy system that dominates US acres, changes in the overall cropping system are needed for sizable greenhouse gas reductions and SOC accrual. This study demonstrated a modeling and experimental framework to quantify and forecast SOC changes created by changing crop root inputs.
培育根系发达、生物量大的一年生作物被认为是增加农田土壤有机碳（SOC）的一种很有前景的干预措施，这对减缓气候变化和改善土壤健康都有益处。在一年生作物中，作为农民固定成本的一部分，每年都会更换遗传技术（种子），这使得针对气候变化的培育解决方案比管理方法更具可扩展性和经济性。然而，对于具有增强根系表型的作物，人们对 SOC 积累潜力的机械理解和定量估计还很缺乏。玉米是美国种植面积最大、产量最高的作物，其根系生物量相对较低，仅限于表土，因此是一种适合改良的作物，如果能迅速推广，改良效果将很可观。我们进行了为期两年的田间试验，以量化从分解同位素标记的玉米根系和分泌物中形成并组成新 SOC（深度达 90 厘米）的过程，包括颗粒态有机物质（POM）、粗颗粒和细颗粒矿物相关有机物质（chaOM 和 MAOM）。此外，我们使用基于过程的 MEMS 2 模型来模拟增强玉米根系理想型的 SOC 积累潜力，假设整体生产力不变，一种方案是将根系生产转移到更深的层次，另一种方案是增加根系生物量的分配。在我们的田间试验中，玉米根系分解优先形成 POM，在 50 厘米以下的效率加倍，而根系分泌物则优先形成 MAOM。模型表明，将根系输入转移到更深的层次或增加根系分配会导致 SOC 的确定性增加，每年每公顷增加 0.05 到 0.15 吨，这处于采用各种作物管理措施后 SOC 每年积累估计值的公布范围的低端。我们的分析表明，对于玉米来说，通过培育增加根系输入作为 SOC 积累的策略，在每公顷的基础上效果有限，尽管全球每年有数亿公顷的玉米种植面积，如果这项技术及其效果得到推广，将会有潜力产生影响。对于以玉米-大豆系统为主导的美国农田，需要对整个种植系统进行改变，才能实现温室气体减排和 SOC 积累。本研究建立了一个模型和实验框架，以量化和预测由改变作物根系输入引起的 SOC 变化。
