Structural and aggregate soil composition under perennial grasses in dark chestnut soil under the Republic of Tyva conditions

The research studies the influence of perennial grasses on the structural and aggregate composition of dark chestnut soil in the conditions of the Tyva Republic. In recent years, there has been a decrease in fertility and a deterioration in the structural and aggregate composition of agricultural soils due to non-compliance with the cultivation technology. At the end of the 2020 growing season, soil samples were taken under perennial grasses of the 3rd year of life. The analysis of the structural composition of the soil by the method of N.I. Savvinov (dry sieving) under the following types of perennial grasses: alfalfa, sainfoin, rump, alfalfa + sainfoin + rump is conducted. It was revealed that under perennial grasses, the structural and aggregate composition of the soil is in good and excellent condition. The best indicators are found under alfalfa crops. The structural coefficient (Kstr) of dark chestnut soil under perennial grasses on the 0-10 cm horizon is excellent, ranging from 1.94 (grass mixture) to 2.47 (alfalfa), in the lower layers 10-30 cm - good. The highest Kstr was recorded in alfalfa crops. Most of the roots that penetrate the soil into small aggregates are in the upper layer; therefore, the soil layer of 0-10 cm is more structured: Sainfoin (67.78 %), rump (66.65 %), alfalfa + sainfoin + rump (66.03 %). The number of agronomically valuable aggregates and the structural coefficient decrease to layers of 10-20 and 20-30 cm. Studies have shown that perennial grasses have a beneficial effect on the formation of an agronomically valuable soil structure in the 0-30 cm layer.