Changes in Fertility of Alluvial Meadow Soil under Different Fertilizer Systems in Vegetable Crop Rotation

In a laboratory and field experiment conducted in the climatic conditions of the Moscow region, it was found that after 2 rotations (6 years) saturated vegetable crop rotation (late white cabbage – carrots – table beets) on alluvial meadow medium loamy soil with annual application of biocompost at a dose of 6 t/ha (total of 18 t/ha), the humus content in the soil stabilized, a tendency to accumulation of alkaline hydrolyzable nitrogen fraction (+6%) was noted and the consumption of mobile forms of phosphorus (–4%) and potassium (–6%), as well as soil decompression. The use of mineral fertilizers in single and one-and-a-half doses revealed a tendency to decrease the content of humus in the soil (by 3–4%), hydrolyzable nitrogen (by 7–8%) and the accumulation of mobile phosphorus (by 1–15%) and potassium (by 3–22%). The introduction of a low dose of mineral fertilizers led to a deterioration of soil fertility, a decrease in the content of humus (–5%), mobile phosphorus and potassium (by 5 and 17%). Slightly more effective was the introduction of biocompost annually at a dose of 3 t/ha. With the joint application of biocompost (6 t/ha) and a single dose of NPK, stabilization of the humus content in the soil at the initial level, accumulation of hydrolyzable nitrogen (by 9%), mobile phosphorus and potassium (by 5–6%) was noted. During 2 rotations, there was a decrease in the content of exchangeable calcium (by 1–10% from the initial level) and magnesium (by 3–11%) and weak acidification of the soil (a decrease in pH_KCl by 1–2% from the initial indicator). It was found that the average productivity of arable land without the use of fertilizers was 50 t/ha, increased by 14 when the half dose was applied, by 28 when the single dose was applied, and by 42% when the half dose was applied, the use of biocompost at doses of 3 and 6 t/ha provided an increase in productivity by 8–16%. With the joint annual application of biocompost with a single dose of NPK, the average productivity of crop rotation increased by 26–35%.