Changes in Soil Fertility and Crop Yields due to Short- and Long-Term Application of Fertilizers in a Grain–Beat Crop Rotation System in the Central Black Earth Region

Abstract

The purpose of this study was to identify changes in soil fertility and yields of main crops in a grain–beat crop rotation system as a result of long-term (ten rotation cycles) application of fertilizers in the Central Black Earth Region. Field works were conducted in Voronezh oblast on a low-humic leached chernozem soil. Changes that have occurred over the period from the first rotation cycle (1936–1945) to the tenth rotation cycle (2018–2022) were analyzed. The experiment involved the following variants: (1) control (no fertilizers), (2) N₁₀P₁₀K₁₀ + manure (2.8 t/ha), (3) N₂₀P₂₀K₂₀ + manure (2.8 t/ha), (4) N₃₀P₃₀K₃₀ + manure (2.8 t/ha), and (5) N₁₀P₁₀K₁₀ + manure (5.6 t/ha). The following changes in soil fertility occurred in the 0–20-cm layer over the period from the first to the tenth rotation cycle due to the effect of fertilizers: (1) in variants with the application of N₂₀P₂₀K₂₀ + manure (2.8 t/ha) and N₃₀P₃₀K₃₀ + manure (2.8 t/ha), hydrolytic soil acidity (H_h) increased by 5.26–83.3%, mobile K₂O content by 18.9–74.4%, cation exchange capacity by 27.8–35.7%, and mobile P₂O₅ content by 7.81–9.00%; (2) in the control variant and variants with the application of N₁₀P₁₀K₁₀ + manure (2.8 t/ha and 5.6 t/ha), humus content decreased by 0.41–0.73%, N-NO₃ content by 25.3–47.7% and P₂O₅ by 13.3–31.6%. Long-term application of fertilizers increased grain yields of barley by 11.3–50.1%, grain yields of oats by 4.0–51.2%, grain yields of winter wheat by 13.4–30.6%, and tuber yields of sugar beet by 15.0–36.7%. In addition, it reduced clover fresh yields by 4.9–27.7% and increased by-product yields in all crops by 6.1–23.0%. Over the period from the first to the tenth rotation cycle, fertilized arable land productivity per 1 ha increased by 3.30–18.3% (less yield increase by 960 grain units/ha due to the introduction of more productive modern varieties). Long-term application of N₃₀P₃₀K₃₀ + manure (2.8 t/ha) ensured the highest level of soil fertility and productivity in the crop rotation system. The fertilization scheme was as follows: N₁₃₅P₁₃₅K₁₃₅ applied to sugar beet fields twice per nine-field crop rotation cycle and manure applied to the fallow field once per crop rotation cycle at a rate of 25 t/ha.