Humus and climate change - results of 15 long-term experiments

The quantification of the impact of climatic change on the content of soil organic matter is of large economic and scientific importance. A suitable possibility for this quantification is the analysis of long-term field experiments, because the carbon and nitrogen contents are continuously measured on those sites, according to the principle of ceteris paribus, over long periods often comprising several decades. For the present study, the results of 15 long-term field experiments on ten different sites with 150 different variations of fertilization were evaluated. The duration of the experiments was between 40 and 110 years (with one exception). The data of the C-org-contents were studied almost complete within a period of 20 years while the contents of N-t were considered within six experiments. The results of the 15 long-term field experiments reveal that on all variants with combined organic-mineral fertilization in the order of magnitude according to the "best practice" and the "method of balance of humus", no depletion of the C-org-contents was detected. Instead, we found a significant increase in various cases. Also in the case of the N-t-contents, no depletion could be detected. A large number of analyses and studies dealing with long-term field experiments of other authors support those results.