Long-term field experiments (LTEs) are invaluable in improving understanding of soil organic matter (SOM) turnover, as some of the involved processes have proceeded over centuries. Prediction of such slow carbon fluxes depends especially on the initialization of slow-reacting model pools and requires monitoring for a very long time for evaluation. This study reports soil organic matter (SOM) modelling covering more than 100 years for a dataset of 36 treatments of the “Extended Static Experiment” that is based on the classical “Static Experiment Bad Lauchstädt.” The experimental scheme includes different fertilization treatments where the plots are arranged in two field stripes. A special feature of this experiment is the management change for each stripe after seven decades of continuous cultivation that includes a considerable alteration of organic amendments on different SOM levels. The Candy Carbon Balance (CCB) model was calibrated for soil organic carbon (SOC) dynamics regarding initial SOC content and one parameter describing the physical protection of SOM. Calibration was performed for each plot individually, for each stripe, and for the whole experiment, resulting in a relative root mean square error (rRMSE, (−)) of 0.050, 0.058 and 0.064, respectively. Model predictions for soil organic nitrogen (SON) dynamics were satisfactory using the calibration results for SOC and the average C/N ratio from all observations within this dataset (11.8) for model initialization. The model error for SON prediction reached from rRMSE = 0.09 (whole experiment) over rRMSE = 0.085 (each stripe) to rRMSE = 0.084 (each plot). Calibration results suggest some heterogeneity between the two field stripes. Restarting the model after the management change in 1978 using the plot-specific calculated SOC value from previous simulations for the whole time period provided different results of predicted SOC trends and values, suggesting that the precondition of SOM in steady state was still not fulfilled after seven decades.

中文翻译：

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应用 CCB 预测管理变化会影响 Bad Lauchstädt 扩展静态施肥实验的长期 SOM 周转率

长期田间试验 (LTE) 对于提高对土壤有机质 (SOM) 周转率的理解非常宝贵，因为其中一些相关过程已经进行了几个世纪。对这种慢速碳通量的预测尤其依赖于慢反应模型池的初始化，并且需要长时间监测以进行评估。这项研究报告了涵盖 100 多年的土壤有机质 (SOM) 建模，该模型基于经典的“Bad Lauchstädt 静态实验”的“扩展静态实验”的 36 次处理数据集。试验方案包括不同的施肥处理，其中地块以两条田间条纹排列。该实验的一个特点是经过 7 年的连续栽培后，每个条纹的管理发生了变化，其中包括在不同 SOM 水平上的有机改良剂的相当大的变化。糖果碳平衡 (CCB) 模型针对土壤有机碳 (SOC) 动态进行了校准，涉及初始 SOC 含量和描述 SOM 物理保护的一个参数。分别对每个图、每个条纹和整个实验进行校准，导致相对均方根误差 (rRMSE, (-)) 分别为 0.050、0.058 和 0.064。使用 SOC 的校准结果和来自该数据集 (11.8) 的所有观测值的平均 C/N 比进行模型初始化，对土壤有机氮 (SON) 动力学的模型预测是令人满意的。SON 预测的模型误差从 rRMSE = 0.09（整个实验）超过 rRMSE = 0.085（每个条纹）到 rRMSE = 0.084（每个图）。校准结果表明两个场条纹之间存在一些异质性。1978 年管理层变更后重新启动模型，使用以前模拟的整个时间段的特定地块计算的 SOC 值，提供了预测的 SOC 趋势和值的不同结果，表明 SOM 在稳定状态的前提条件在 7 之后仍未满足几十年。