Changes in the acid-base properties of soddy-podzol soil with time and along the profile, resulting from long-term use of fertilizers under the conditions of the Cis-Urals

The influence of long-term use of organic, mineral and organomineral fertilizer systems leveled by nutrients (control – without fertilizer application; cattle manure 10 and 20 t/ha per year; NPK equivalent to 10 and 20 t of manure; manure 5, 10 and 20 t + NPK equivalent to 5, 10 and 20 tons of manure) on the exchangeable (pHKCL), hydrolytic acidity (Actot), the sum of exchangeable bases (S) and the degree of soil saturation with bases (V) is considered. The field experiment was performed in 1969–1970 at the Perm Research Institute of Agriculture, on soddy slightly podzolic heavy loam soil. Field crop rotation included 8 fields. Data are presented for each cycle of crop rotation (1969–2017) in the arable soil layer and at the end of rotation VI (2016–2017) in the meter layer. The effect of fertilizers on soil properties was studied against the background of liming (at a dose of 1.0 Actot), which was carried out in the first rotation. The greatest efficiency of liming was observed in the first two rotations; a gradual deterioration in pHKCL, Actot, S and V was noted from the third rotation in all variants of the experiment; the degree of changes differed significantly depending on the fertilizer system used. Application of cattle manure at the rate of 10 t/ha per year restrained the deterioration of the acid-base properties of the soil (relative to the control variant); application of 20 t/ha per year ensured in III–VI rotations at least the maintenance of the studied soil properties at the initial level (before liming) or contributed to their improvement. The positive effect of manure on pHKCL, Actot and V indicators was observed mainly in the soil layer of 0–40 cm. The use of a mineral fertilizer system led to acidification of the soil and a decrease in V. The pHKCL, Actot and V indicators in the “NPK eq. 20 t/ha of manure” in V–VI rotations were significantly lower than the initial level (pHKCL before liming – 5.5, II rotation – 5.9, V–VI rotation – 4.5–4.6; Actot – 3.1, 2.5 and 3.7–4.4 cmol(eq)/kg; V – 84, 90, 80–82%, respectively). The adverse effect of mineral fertilizers on pHKCL, Actot and V after application of NPK eq. 20 t/ha of manure (N70P50K100 per year) was observed in a meter layer, NPK eq. 10 t/ha of manure (N35P25K50 per year) – in the arable layer. The organomineral fertilizer system occupied an intermediate position between mineral and organic ones in terms of its effect on pHKCL, Actot, S and V; processes of soil acidification were observed, but they were less pronounced.