Soil pH Changes in Long-Term Field Experiments with Different Fertilizing Systems

The changes of soil pH in long-term 14-year field experiments with different fertilizing systems are described. The field experiments were located at four sites of the Czech Republic with different soil and climatic conditions (Cerveny Ujezd, Hneveeves, Lukavec, and Prague-Suchdol). At each site, the same fertilizing systems and crop rotation (potatoes winter wheat spring barley) were established. Six experimental treatments were applied to crop rotation: (1) unfertilized treatments (control); treatments with organic fertilization: (2) farmyard manure (FYM), (3) sewage sludge (SS); treatments with mineral fertilizers: (4) nitrogen (N), (5) nitrogen with straw application (N + straw), and (6) nitrogen with phosphorus and potassium (NPK). The long-term effect of fertilizers significantly depends on soil conditions. At the site Prague-Suchdol minimal differences in the soil pH were observed by all treatments. This is caused by the high buffering capacity of Chernozems against the soil acidification. At Cerveny Ujezd (Haplic Luvisol), Hneveeves (Haplic Luvisol), and Lukavec (Stagnic Cambisol) sites, soil pH decreased by all treatments. Only at Hneveeves site the soil pH did not change with N treatment. The highest soil pH decrease in the treatment with NPK (Delta pH -0.89) and N + straw (Delta pH -0.70) was observed at Hneveeves site. By the treatments FYM and SS the highest decrease was registered at Cerveny Ujezd (Delta pH of about -0.30 and -0.63, respectively). The highest decrease in control treatment (Delta pH of about -0.63) was observed at Lukavec site. The results showed that to evaluate long-term soil pH changes a whole complex of factors must be examined.