Kwon Hoyoung, Ugarte Carmen M, Ogle Stephen M, Williams Stephen A, Wander Michelle M
Environment and Production Technology Division, International Food Policy Research Institute, Washington, DC, United States of America.
Department of Natural Resources and Environmental Sciences, University of Illinois, Urbana, IL, United States of America.
PLoS One. 2017 Feb 24;12(2):e0172861. doi: 10.1371/journal.pone.0172861. eCollection 2017.
We evaluated the accuracy and precision of the CENTURY soil organic matter model for predicting soil organic carbon (SOC) sequestration under rainfed corn-based cropping systems in the US. This was achieved by inversely modeling long-term SOC data obtained from 10 experimental sites where corn, soybean, or wheat were grown with a range of tillage, fertilization, and organic matter additions. Inverse modeling was accomplished using a surrogate model for CENTURY's SOC dynamics sub-model wherein mass balance and decomposition kinetics equations from CENTURY are coded and solved by using a nonlinear regression routine of a standard statistical software package. With this approach we generated statistics of CENTURY parameters that are associated with the effects of N fertilization and organic amendment on SOC decay, which are not as well quantified as those of tillage, and initial status of SOC. The results showed that the fit between simulated and observed SOC prior to inverse modeling (R2 = 0.41) can be improved to R2 = 0.84 mainly by increasing the rate of SOC decay up to 1.5 fold for the year in which N fertilizer application rates are over 200 kg N ha-1. We also observed positive relationships between C inputs and the rate of SOC decay, indicating that the structure of CENTURY, and therefore model accuracy, could be improved by representing SOC decay as Michaelis-Menten kinetics rather than first-order kinetics. Finally, calibration of initial status of SOC against observed levels allowed us to account for site history, confirming that values should be adjusted to account for soil condition during model initialization. Future research should apply this inverse modeling approach to explore how C input rates and N abundance interact to alter SOC decay rates using C inputs made in various forms over a wider range of rates.
我们评估了CENTURY土壤有机质模型在美国雨养玉米种植系统下预测土壤有机碳（SOC）固存的准确性和精确性。这是通过对从10个试验地点获取的长期SOC数据进行反向建模实现的，在这些试验地点，玉米、大豆或小麦在一系列耕作、施肥和添加有机质的条件下种植。反向建模是使用CENTURY的SOC动态子模型的替代模型完成的，其中CENTURY的质量平衡和分解动力学方程通过使用标准统计软件包的非线性回归程序进行编码和求解。通过这种方法，我们生成了与氮肥施用和有机改良对SOC衰减的影响相关的CENTURY参数统计数据，这些影响的量化程度不如耕作和SOC初始状态的影响。结果表明，在反向建模之前，模拟的SOC与观测的SOC之间的拟合度（R2 = 0.41）可以提高到R2 = 0.84，主要是通过将氮肥施用量超过200 kg N ha-1的年份中SOC衰减率提高到1.5倍。我们还观察到碳输入与SOC衰减率之间存在正相关关系，这表明通过将SOC衰减表示为米氏动力学而不是一级动力学，可以改进CENTURY的结构，从而提高模型准确性。最后，根据观测水平对SOC初始状态进行校准，使我们能够考虑场地历史，确认在模型初始化期间应调整值以考虑土壤条件。未来的研究应应用这种反向建模方法，以探索碳输入速率和氮含量如何相互作用，从而使用更广泛速率范围内的各种形式的碳输入来改变SOC衰减率。
