Crop rotation links influence on the organic matter regime of southern chernozem in steppe agrocenosis

The objective of the study is to identify the influence of agricultural crops and crop rotation links on the organic matter regime of southern chernozem in the steppe zone of the Southern Urals and to develop biological methods for its stabilization. The studies were conducted as part of a longterm stationary field experiment in the arid steppe conditions of the Orenburg CisUrals. The soil of the experimental plot is southern chernozem, lowhumus, mediumdeep, carbonate, heavy loamy with a humus content of 4.4 % and a slightly alkaline reaction of the soil solution (pHH2O – 7.8). The experimental design included seven crop rotation links of different composition and fertilizer system with a rotation of 3 years. The experiment was carried out in accordance with generally accepted methods. The placement of options is systematic in two tiers, the area of the experimental plots is 486 m2. The experiment was repeated three times in time and four times on the territory. A comparative assessment of field, forage crops and crop rotation links was carried out in terms of productivity, the amount of plant organic matter entering the soil and the volume of newly formed humus. For the conditions of dry farming in the steppe zone of the Southern Urals, a wider use of green manure and byproducts of plant growing was proposed as additional resources of plant organic matter for the reproduction of soil fertility, effective crop rotation links were developed to ensure stabilization of the humus state of the soil, and recommendations were given for optimizing the structure of crop rotations. The largest input of stubble and root residues into the soil (22.18–22.91 t/ha) was provided by the links with forage grasses. For a positive humus balance in the agrocenoses of the steppe zone, it is necessary to include forage grasses and green manure crops in the composition of field crop rotations, use byproducts as an additional source of plant organic matter, use occupied fallows instead of clean fallows, or apply manure at a rate of at least 20 t/ha.