Influence of long-term use of nitrogen, phosphorus and potassium fertilizers on crop yields, the balance of organic carbon and nutrients

The efficiency of using nitrogen, phosphorus and potash fertilizers (N90, P90, K90, N90P90, N90K90, P90K90, N90P90K90, N30P30K30, N60P60K60, N120P120K120, N150P150K150) in a long-term experiment (year of establishing– 1978, Permian Research Institute) on sod-podzolic heavy loamy soil in a field 8-pole crop rotation was evaluated. It was found that in the climatic conditions of the Urals, the use of N90 on winter rye and oats was the most effective (taking into account the payback of 1 kg of a.s. NPK with 1 kg of main products), on potatoes – (NPK)30–60, spring wheat – N60P60K60, barley – N30P30K30. There was no significant effect of mineral fertilizers on the yield of meadow clover hay of the 1st and 2nd year of use. Crop rotation productivity increased by 12–25% on average over 5 rotations when using N90, N90P90, N90K90, P90K90, and (NPK)30–150. The maximum productivity was obtained in the N60P60K60 variant – 3.31 tons of grain, the highest payback was achieved when applying nitrogen fertilizers N90 (8.9 kg of grain). At the same time, prolonged use of the mononitrogen fertilizer system led to a deterioration in soil fertility. The use of superphosphate and potassium chloride in its pure form did not significantly affect the productivity of crop rotation. The balances of organic carbon and mineral nutrition elements were calculated. A positive carbon balance was obtained using high doses of N120P120K120 and N150P150K150 (+0.06–0.13 t/ha/year), only in these variants the maintenance of the Corg content in the soil layer (0–20 cm) at the initial level was noted. The nitrogen balance, which is close to zero and positive, was formed when nitrogen fertilizers were applied at a dose of 90–150 kg a.s./ha. A positive phosphorus balance was obtained by applying superphosphate at a dose of 60 kg a.s./ha and more. A zero and positive potassium balance was formed when potassium chloride was used at a dose of 120–150 kg a.s./ha.