Effect of tillage systems on changes in the aggregate composition of dark gray forest soils in the Northern Trans-Urals

Abstract

In a long-term stationary experiment (1988-2019) the impact of mouldboard, non-mouldboard, combined, differentiated, surface and sweep-blade tillage systems on the change in the aggregate composition of dark gray forest soils was studied. The research took place in the northern foreststeppe of the Northern Trans-Ural (Tyumen Region). Over a 30-year period of use in arable land, the soil of 0-20 cm layer retained its structural condition not inferior to the initial one for most of the studied variants of cultivation. With increasing the depth of the soil profile up to 0-30 cm layer due to an increase in the proportion of clumpy fraction in the lower layer 10-30 cm there was a decrease in the content of agronomically valuable structure compared to the layer 0-20 cm, as well as with the initial state on most of the studied systems of cultivation. The highest content of agronomically valuable structure in the soil layer 0-20 cm was on the mouldboard, sweep-blade and differentiated tillage systems (72.8-77.8%). Over the 30-year period, the agronomically valuable structure content (10-0.25 mm) in the soil layer 0-20 cm increased by 6.12-13.45% in these treatments, the structure coefficient by 21.9-60.3%. For the other treatment systems, the content of this fraction (67.5-69.8%) and the structure coefficient (2.07-2.31) were close to the initial condition - 68.6% and 2.19, respectively. The average weighted diameter of agronomically valuable aggregates increased from 2.71 mm in the initial condition to 3.00-3.29 mm (7.7-21.2%) due to a significant increase in the proportion of these aggregates in the 0-10 cm layer. In general, the highest indicators of the structural condition of the soil profile of 0-30 cm remained on the mouldboard, sweep-blade and differentiated systems of cultivation. Non-mouldboard, combined and surface tillage reduced the content of agronomically valuable structure by 9.7-15.9% compared with the mouldboard system, and led to a decrease in the coefficient of structure by 0.99-1.39 units.