ABSTRACT

The application of organic fertilizers (OF) can supply carbon (C) to the soil in crop fields. OF-derived C (OF-C) is often estimated using the differential method that can be biased due to indirect effects of OF on soil C. This study tested three methods to quantify OF–C: (i) the widespread differential method, (ii) the synchronic isotope method comparing plots with and without OF and (iii) the asynchronic isotope method mimicking a trial without a control plot. These methods were implemented on an Arenosol and an Andosol supplied during 13 years with slurry or compost. The results highlighted the relevance of using the synchronic isotope method, which focuses on the direct effect of OFs on the soil organic matter (without bias of vegetation change) and considers control soil’s evolution. The higher the isotopic difference between soil and OF, the shorter the method implementation time needed: for an initial difference of 7.5 ‰ and 3.5 ‰, quantification is suitable after 4 and 9 years of fertilization respectively. Attention should be paid to OF-δ¹³C variability to guarantee the method validity. The method proved to be suitable to study the factors controlling the OF-C fate in tropical soils.

摘要

施用有机肥（OF）可以为农田土壤提供碳（C）。由于 OF 对土壤​​ C 的间接影响，OF 衍生的 C (OF-C) 通常使用微分方法进行估计。本研究测试了三种量化 OF-C 的方法：（i）广泛使用的微分方法，（ ii) 比较有和没有 OF 的图的同步同位素方法和 (iii) 模拟没有对照图的试验的异步同位素方法。这些方法在使用泥浆或堆肥的 Arenosol 和 Andosol 上实施了 13 年。结果强调了使用同步同位素方法的相关性，该方法侧重于 OFs 对土壤有机质的直接影响（没有植被变化的偏差）并考虑控制土壤的演变。土壤和 OF 的同位素差异越大，方法实施时间越短：对于7.5‰和3.5‰的初始差异，分别在施肥4年和9年后量化。应注意OF-δ¹³ C 变异性以保证方法的有效性。该方法被证明适用于研究控制热带土壤中 OF-C 归宿的因素。