Effects of LongTerm Application of Mineral Fertilizers and Manure on Agrochemical Properties of Gray Forest Soil, Crops Productivity and Carbon Sequestration

Abstract

The effect of long-term application of increasing doses of mineral (from N90P75K100 to N360P300K400) and organic (cattle manure from 25 to 100 t/ha) fertilizers on the fertility of gray forest soil was studied in the micro-plot experiment. Over 9 years, 0.81–3.24 t/ha of nitrogen, 0.68–2.70 t/ha of P2O5 and 0.90–3.60 t/ha of K2O were applied with mineral fertilizers. Manure supplied 43–173 t/ha of dry matter, 16–65 t/ha of Corg, 0.85–3.41 t/ha of Ntot, 0.65–2.59 t/ha of P2O5 and 0.86–3.46 t/ha of K2O. In the yield the mineral fertilizer system exceeded the organic one by an average of 29%. At extreme doses (N360P300K400 and 100 t/ha of cattle manure) mineral fertilizers reduced crop productivity more strongly than organic fertilizers. A direct linear relationship was found between the doses of mineral and organic fertilizers and the increase in the content of available P2O5 and K2O in the soil. Application of extreme doses of fertilizers did not lead to saturation of the soil with available forms of phosphorus and potassium. Long-term application of organic fertilizers increased the soil pH(KCl) by 0.4–1.3 units and mineral fertilizers decreased it by 0.8–1.4 units. Annual application of mineral fertilizers increased soil Corg content by an average of 0.02–0.04% per year, and organic fertilizers – by 0.08–0.17% per year. Manure application at 100 t/ha over 9 years led to the saturation of the soil with organic carbon. The C : N ratio in the soil under a mineral fertilizer system was decreased, while it with the organic system was increased. An approach to calculate the carbon sequestration efficiency for the assessment of different agronomic practices is proposed. It is shown that the carbon sequestration efficiency of the organic fertilizers was 15% higher than that of the mineral fertilizers.