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 paper considers a biological factor affecting the reproduction of humus and the maintenance of soil fertility in a region with unstable moisture. In the steppe zone of the Southern Urals, the humus formation process is affected by the amount of plant (stubble-root) residues entering the soil, which suggests the possibility of reducing the mineral fertilizers use. The purpose of the experiment was to determine the affecting of a set of field crops in crop rotations on the input of organic matter into the soil of the southern chernozem. The paper studies three variants of the experiment with different types of fallow. An increase of humus in the soil by 0.17% (in the percentage) was found in the crop rotation with fallow occupied by the summer sowing of Sudanese grass in comparison with grain-fallow with weed-free fallow. On average over 10 years, the largest volume of organic matter entered the soil during the cultivation of winter rye in a crop rotation with weed free-fallow (11.87 tons per 1 ha).

The recombination ability of the breeding material is an important feature that must be taken into account when cultivars involve in hybridization. The recombination ability of the basic seed millet material was established based on the analysis of long-term data on cross-breeding combinations and the output of promising lines in a competitive test. The analysis showed that not all varieties of the Orenburg breeding, both in direct and reverse crosses, had a high coefficient of recombination potential. Based on the results obtained, the varieties that are better included in the hybridization as the mother line were identified, since the coefficient of recombination ability is higher in direct crosses. Also there were varieties which is advisable to inclusion in the breeding process only in reverse crosses.

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.