Influence of Cultivation Technology on the Productivity of Spring Wheat and the Humus State of Southern Carbonate Soils of Northern Kazakhstan

Intensive use of the chernozem soils of Northern Kazakhstan since the development of virgin lands has led to soil erosion and loss of humus. Since 1954, according to researchers, 1.2 bln tons of organic matter have been irretrievably lost. During this period, the methods of tillage have changed significantly from surface to subsurface tillage, which led to a change in the method of accumulation of organic residues in the soil. The purpose of this study was the short-term monitoring of spring wheat cultivation technologies to observe their influence on crop productivity and soil agrocenosis. A virgin plot was used as a standard of soil fertility. Determination of nutrients in the soil was carried out by using the method of "wet chemistry" with spectrophotometric termination. An infrared analyzer was used to assess the grain quality. The identification of soil microorganisms was carried out on nutrient microbiological media, such as meat-and-peptone agar, starch-and-ammonia agar, and Czapek-Dox agar. The results of three-year studies showed that the humus content in the variants with permanent wheat decreased to 3.26–3.38%. The greatest decrease in humus content was observed in the two-field grain and fallow crop rotation (2.48%). The decrease in the amount of humus occurred as a result of insufficient intake of plant residues and mineral fertilizers. The content of nitrate nitrogen and mobile phosphorus in virgin soil is low. Soil micromycetes dominate on virgin lands, whereas ammonifiers and immobilizers dominate on cultivated soils. The high level of carbon dioxide emissions on virgin land (3.0 C2 kg/ha/hour) is due to the presence of a large amount of plant biomass. The most optimal variant out the considered technological backgrounds from the point of view of increasing yields up to 15.8 c/ha and preserving soil fertility (3.26% humus content) is the cultivation of permanent wheat with the introduction of fertilizers and herbicides. The use of two-field grain and fallow crop rotation leads to irreplaceable losses of organic matter (2.48%).