Simple humus balance calculators were developed for farmers and consultants to determine the best crop rotation and amount of organic fertilizer required to improve soil quality and prevent nutrient leaching in croplands. Although the potential of these tools to infer the impact of different agricultural practices on soil organic carbon (SOC) dynamics in croplands is not well studied, they have been integrated in several farm‐level climate or environmental impact assessment calculators. Here we examine the correlation between humus balance values estimated with two different tools developed in Germany/Central Europe and observed changes in SOC content at 14 long‐term sites in Switzerland. The first tool was developed by the Association of German Agricultural Investigation and Research Institutes and is referred to as the VDLUFA. The humus balance calculator STAND is a descendent of the VDLUFA that accounts for pedoclimatic factors in Central Europe. Crop rotations were distinguished based on cultivation practice, whereby those with mixed fertilization were supplied with mineral fertilizer alone and in combination with organic materials, while those with organic fertilization include unfertilized and organic fertilizer treatments. An analysis of 133 short‐term observations (i.e. individual crop rotations of five and 6‐year duration) and 26 long‐term observations (i.e. several crop rotations with a total duration of ≥10 years) showed that humus balance values (kg C ha−1 year−1) of short‐term crop rotations were not or only poorly correlated with the observed change in SOC content (%) (R2 = 0.06 in STAND and R2 = 0.05 in VDLUFA for crop rotations with organic fertilization, and R2 < 0.01 for crop rotations with mixed fertilization). The correlation did not improve when the humus balance values of long‐term observations with mixed fertilization were compared with decadal SOC development (R2 = 0.04 for STAND and R2 = 0.06 for the VDLUFA). Stronger correlations were found only for long‐term observations with organic fertilization (R2 = 0.68 for STAND and R2 = 0.64 for the VDLUFA). These findings underline that while the studied humus balance calculators are able to distinguish the effect of different fertilizers (organic vs. mineral) on a farm's humus supply on the longer term, neither are suited for predicting SOC trends over single crop rotations. Although this study was carried out in Switzerland, the results should apply to any region with temperate climate and similar soil properties.

中文翻译：

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简单腐殖质平衡计算器（VDLUFA 和 STAND）的输出与土壤有机碳趋势之间没有关系


为农民和顾问开发了简单的腐殖质平衡计算器，以确定改善土壤质量和防止农田养分浸出所需的最佳作物轮作和有机肥量。尽管这些工具在推断不同农业实践对农田土壤有机碳 （SOC） 动态影响方面的潜力尚未得到充分研究，但它们已被整合到几个农场层面的气候或环境影响评估计算器中。在这里，我们研究了使用德国/中欧开发的两种不同工具估计的腐殖质平衡值与在瑞士 14 个长期地点观察到的 SOC 含量变化之间的相关性。第一个工具由德国农业调查和研究机构协会开发，被称为 VDLUFA。腐殖质平衡计算器 STAND 是 VDLUFA 的后代，它考虑了中欧的土壤气候因素。作物轮作根据栽培实践进行区分，其中混合施肥的作物单独施用矿物肥料并与有机材料结合使用，而施有机肥的作物包括未施肥和有机肥处理。对 133 次短期观察（即 5 年和 6 年持续时间的单个作物轮作）和 26 次长期观察（即总持续时间为 ≥10 年的几次作物轮作）的分析表明，短期作物轮作的腐殖质平衡值（kg C ha-1 年-1）与观察到的 SOC 含量变化 （%） 没有或仅相关性很差（对于有机施肥的作物轮作，RAND 中的 R2 = 0.06，VDLUFA 中的 R2 = 0.05）， 和 R2 < 0.01 用于混合施肥的作物轮作）。 当将混合施肥的长期观测的腐殖质平衡值与年代际 SOC 发育进行比较时，相关性没有提高 （STAND 的 R2 = 0.04，VDLUFA 的 R2 = 0.06）。仅在有机施肥的长期观察中发现更强的相关性 （STAND 的 R2 = 0.68 和 VDLUFA 的 R2 = 0.64）。这些发现强调，虽然所研究的腐殖质平衡计算器能够区分不同肥料（有机肥料与矿物肥料）对农场腐殖质供应的长期影响，但两者都不适合预测单一作物轮作的 SOC 趋势。虽然这项研究是在瑞士进行的，但结果应该适用于任何具有温带气候和相似土壤特性的地区。