Increasing the yield of barley cultivated in crop rotations and by sowing permanently is a major problem in the steppe zone of the Southern Urals. This requires to study factors affecting an increase in the crop yield. The aim of the study is to identify the effect of nitrate nitrogen, the biological activity of soil and the aftereffect of predecessors on barley productivity at different levels of mineral nutrition. In the experiment, methods such as field, ionometric and decomposition of flax fiber were used. The methods used make it possible to obtain new original results on the factors and experimental options. Over 18 research years, the highest barley yield was observed in millet and pea rotation using fertilizers. It amounted to 1.42 and 1.43 tons per 1 ha. These results were achieved due to the consumption of nitrate nitrogen up to 2.3 mg and accumulation in the amount of 7.7 mg per 100 g of soil with an activity of microorganisms of 8.3 and 8.1 %. The results are of scientific and practical importance in the field of agriculture and crop production.

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The article outlines the problems of dry farming in the Orenburg region. The reasons for the degradation of chernozem soils leading to their complete destruction and ecological catastrophe are shown. The ways of solving and scientifically substantiated possibilities of preserving the soil fertility of the Orenburg chernozems, which increase productivity, reduce to a minimum the negative effect of drought. during the transition to contour-landscape agriculture, it was established that it was possible to obtain stable yields every year in all natural and climatic zones of the Orenburg region. Studied five-field crop rotations with various types of occupied and black fallow in relation to contour landscape agriculture (CLA). The average grain yield according to the experience was -16.1 centners, including spring wheat - only 18.6 centners per hectare. Grain output from 1 hectare of crop rotation -12.9 centners. The productivity of the experiment on the average of the steaming grass was 2.17 thousand feed units. The green mass of the cereal-legume mixture (barley + peas) in the green manure pair is 1.67 thousand fodder units. The production of the buffer strip amounted to 2.26 thousand fodder units of green mass of Sudanese grass per hectare

The detection of factors that affect the decrease in the productivity of durum wheat is the basis for the study of plant diseases in the soil and climatic conditions of the southern chernozems of the Cis-Ural region. On the basis of this premise, for the first time, studies on common root rot (Bipolaris sorokiniana) of durum wheat are conducted in field and laboratory conditions. There is the method of field experience, stationary accounting of agrometeorological conditions and disease determination is used. The results of six years research show that in the third variant of the experiment, the least spread and development of root rot is observed on a non-windy background of nutrition up to 28.6 and 10.2%. The dependence on the influence of air temperature is 94.4 and 70.0%. The highest crop yield of durum wheat was obtained in the average dry year of 2017 according to the green-manured fallow predecessor. It consists of 21.4 c on fertilized and 21.1 c per 1 ha on non-winded backgrounds of mineral nutrition. The maximum effect of root rot development on the decrease in durum wheat productivity is noted in the fourth version of the experiment and it consists of 80.04 and 89.66% on two nutrition backgrounds. The study results have a scientific and practical importance in the field of phytopathology, farming and intensive agriculture.

The main source of soil fertility decline in the arid conditions of the Orenburg region is erosion, which manifests itself to varying degrees over the entire arable land. In the Orenburg region, 2214.9 ha are subject to water erosion, wind erosion - 279.4 ha, and out of a total area of 6240.0 thousand hectares, deflationary hazardous erosion - 5304.3 thousand hectares. In connection with erosion processes, the humus content in the soil decreases by 1-6 tons in southern chernozems, ordinary -1.7%. The studies were carried out in two stationary areas of the Orenburg Cis-Urals and Trans-Urals in order to determine the efficiency of measures and technologies to preserve soil fertility and protect the soil from erosion in arid conditions. With the transition to contour-landscape agriculture (CLA), the fertility of slope lands and the yield of field crops increases, and the negative effect of drought decreases to a minimum. The decrease in soil fertility caused by the erosion process is recorded in the fallow field when it is allocated for spring wheat. Soil-protecting and green fallows largely eliminate this disadvantage. During the fallowing period as per the data, the field of black fallow accumulates 430 kg per 1 ha of nitrates in the 0-150 cm layer, and when mineral fertilizers are applied at a dose of N40P80, it increases to 689 kg per 1 ha.