Agricultural management affects active carbon and nitrogen mineralisation potential in soils

Soil organic matter (SOM) is important for soil fertility and climate change mitigation. Agricultural management - including soil amendments - 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. The current study aimed at understanding how sensitive the parameters active/permanganate oxidisable carbon (AC) and nitrogen mineralisation potential (NMP) react to different agricultural management practices compared to total organic carbon (TOC) and total nitrogen (Nt). We aimed to gain a better understanding of SOM processes, mainly regarding depth distribution and seasonality of SOM dynamics using AC and NMP.

Data were obtained in five Austrian long-term field experiments (LTEs) testing four management practices: i) tillage, ii) compost application, iii) crop residue management, and iv) mineral fertilisation.

AC was specifically sensitive in detecting the effect of tillage treatment at different soil depths. NMP differentiated between all different tillage treatments in the top 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 Nt over the course of two years in the crop residue LTE. Thus, 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 Nt. They should be integrated in monitoring agricultural LTEs and in field analyses conducted by farmers. However, when evaluating results of long-term carbon storage, their sensitivity towards annual fluctuations should be taken into account.