Changes in the Agrochemical Properties of Albic Retisol (Abruptic, Aric, Loamic) during a Long-Term Use of Nitrogen, Phosphorus, and Potassium Fertilizers under Cis-Ural Conditions

The effects of long-term application of nitrogen, phosphorus, and potassium fertilizers on the changes in the content of organic carbon, mineral nitrogen, available phosphorus and potassium, and soil adsorption complex parameters of soddy-podzolic soil (Albiс Retisol (Abruptic, Aric)) were studied. The research was carried out in a one-meter soil layer in a long-term stationary experiment founded in 1978 in Perm region. The direction, character, and intensity of changes in the soil agrochemical properties depended on the type and combination of fertilizers (N, P, K, NP, NK, PK, and NPK). Ammonium nitrate or urea, double or simple superphosphate, and potassium chloride were used in the experiment at a rate of 90 kg of active ingredient per hectare. It was revealed that long-term use of nitrogen fertilizers (N 90 ) led to significant losses in the organic soil carbon to a depth of 40–60 cm; the stock of organic carbon in 1-m soil layer decreased by almost 30%. Long-term use of potassium chloride (K 90 ) promoted the rise in the content of organic carbon in this soil layer, elevating its stock by 40%. Long-term application of superphosphate (P 90 ) alone had no significant effect on the changes in C org along the soil profile. Nitrogen fertilizers used both alone and in combination with phosphorus and potassium (NP, NK, and NPK) caused a considerable soil acidification. A decrease in pH KCl value and an increase in hydrolytic acidity were observable down to a depth of 40–60 cm or in 1-m soil layer. An increase in the mineral nitrogen content in the soil was noted in given variants. The intensity of mineral nitrogen migration along the profile depended on the combination of fertilizer types.. Potassium chloride in combination with superphosphate (P 90 K 90 and N 90 P 90 K 90 ) enhanced the migration of phosphorus along the profile. The content of available phosphorus compounds increased to a depth of 60–80 cm or in the 1-m soil layer. Superphosphate neutralized the effect of nitrogen or potassium fertilizers on soil fertility.