The Long-term Soil Fertility Experiments in Southern Sweden

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Abstract
The dynamics of soil organic matter (SOM) in the long-term soil fertility experiments in Skåne, southern Sweden, was analysed statistically and by means of a simulation model. In the simulation model, SOM is treated as two pools, a labile pool and a stable one. The input of organic matter to the labile pool is assumed to depend on crop yield and the application rate of farmyard manure. First-order rate kinetics is used to describe the decomposition process. A method for fitting differential equations to data was used to estimate the parameters in the model and the initial size of the labile pool for the various fields. The results were compared with results from laboratory incubation experiments and with data on crop removal of soil N. The statistical analysis showed that the changes with time (trends) in N content in soil were significantly affected by rotation and N fertilization, and there were significantly different trends between fields. The simulation model best described the dynamics of soil N in situ when turnover times between 30 and 70 years were used for the labile pool. The effects of treatments on C and N mineralization in the incubation experiments were best described using turnover times between 30 and 40 years.