Agricultural management affects active carbon and nitrogen mineralisation potential in soils

Background Soil organic matter (SOM) is important for soil fertility and climate change mitigation. Agricultural management can improve soil fertility and contribute to climate change mitigation by stabilising carbon in soils. This calls for cost-effective parameters to assess the influence of management practices on SOM contents. Aims The current study aimed at understanding how sensitively the parameters active carbon (AC) and nitrogen mineralisation potential (NMP) react to different agricultural management practices compared to total organic carbon (TOC) and total nitrogen (N-t). We aimed to gain a better understanding of SOM processes, mainly regarding depth distribution and seasonality of SOM dynamics using AC and NMP. Methods We looked mainly at four parameters, namely permanganate oxidisable carbon (AC), nitrogen minerlaisation potential (NMP), total organic carbon (TOC) and total nitrogen (N-t). Data were obtained in five long-term field experiments (LTEs) testing four management practices: (1) tillage, (2) compost application, (3) crop residue management, and (4) mineral fertilization. Results AC was specifically sensitive in detecting the effect of tillage treatment at different soil depths. NMP differentiated between all different tillage treatments in the upper soil layer, it showed the temporal dynamics between the years in the compost LTE, and it was identified as an early detection property in the crop residue LTE. Both AC and NMP detected short-term fluctuations better than TOC and N-t over the course of two years in the crop residue LTE. Conclusion We suggest that AC and NMP are two valuable soil biochemical parameters providing more detailed information on C and N dynamics regarding depth distribution and seasonal dynamics and react more sensitively to different agricultural management practices compared to TOC and N-t. They should be integrated in monitoring agricultural long-term experiments (LTEs) and in field analyses conducted by farmers. However, when evaluating results towards long-term carbon storage, their sensitivity toward annual fluctuations should be taken into account.