Organic Carbon Content in Structural Units of Leached Chernozem With Increasing Doses of Mineral Fertilizers in the Forest-Steppe Zone of the Urals

Abstract

Carbon reserves concentrated in the soil determine its fertility and buffering capacity. Structural aggregates are formed due to organic matter, which serves as a binding material in the formation and stabilization of soil structural units. Intensive use of soil during cultivation of agricultural crops has a significant impact on its biological activity. This leads to significant changes in the natural process of soil evolution and its degradation. The objective of the study was to determine the effect of mineral fertilizers on the content and reserves of organic carbon in various structural units of leached chernozem in the forest-steppe zone of the Urals. Long-term use of soil for arable land without the application of mineral fertilizers worsens the soil structure Kstr=1.6 units. Fertilizers applied in the calculation of obtaining 3.0 and 4.0 t/ha of grain contribute to the improvement of the soil structure (Kstr=2.0 ... 2.1 units). The maximum amount of organic carbon (Corg) in the control variant was noted in aggregates > 10 and < 0.25 mm in size - 4.77 and 4.61%. Systematic application of fertilizers in the calculation of the formation of 3.0 and 4.0 t/ha of grain provides an increase in Corg content in soil aggregates from 1.0 to 0.25 mm in size by 0.70 ... 0.72%. When applying fertilizers for the planned yield of 5.0 t/ha, a loss of carbon from aggregates of 10 ... 3 mm in size is observed by 0.45%. At the maximum agricultural background, Corg content in aggregates > 10 and < 0.25 mm decreases to 3.70 and 4.11%. In the control Corg reserves in agronomically valuable aggregates reach 59.3% of the total reserves. Systematic application of fertilizers based on a yield of 3.0 ... 4.0 t/ha of grain increases the carbon reserves in valuable soil aggregates to 66.2 ... 68.0% of the total reserves. Planning higher yields leads to a decrease in carbon reserves in agronomically valuable aggregates.