Long-term effects of potassium on parameters of the soil water balance

Long-term field experiments provide excellent opportunities to quantify the long-term effects of husbandry on physical soil properties. Therefore the aim of the study was to quantify the effect of various long-term potassium treatments on ecologically and soil fertility relevant parameters based on the assessment of two long-term field experiments in Germany. Special emphasis was placed on the parameters field capacity, available water capacity, different pore spaces and field air capacity. In this paper, results for field capacity and available water capacity are presented. In our study it was possible to prove an effect of the potassium fertilisation on important soil physical and soil chemical parameters. The results of the chemical analysis underline a complex effect of the potassium fertilisation. On both experimental sites, a close positive correlation between soil potassium content and soil organic substance was found in the treatments without farmyard manure (FYM). Regardless of the experimental site, the plant available water capacity was increase after a long-term potassium fertilisation. This had, however, no negative effect on the field air capacity. Given the various methods applied in this study, it was not possible to completely explain the results of the effect of a different potassium fertilisation on plant available water capacity.