FALLOW CROPS PRODUCTIVITY AND THE ROLE OF FALLOW UNDER DRID CONDITIONS OF THE SOUTHERN URALS STEPPE ZONE

The purpose of the study is to establish the influence of meteorological factors, the content of productive moisture and macroelements in the soil on the productivity of fallow crops in a system of six-field crop rotations on two agricultural backgrounds in the conditions of the steppe zone of the Southern Urals. Long-term studies were carried out from 1993 to 2022 in the Orenburg Region. Location coordinates of the stationary experiment site are: 51.775125 latitude and 55.306547° v.d. Sudanese grass of summer sowing, peas and oats were used as fallow crops. The objects of study (Sudan grass and pea-oat mixture) were cultivated on two agricultural backgrounds: fertilized with N40P80K40 and without the use of mineral fertilezers. The content of macroelements in the soil was determined by the ionometric method according to Tyurin (N-NO3), according to Machigin (mobile phosphorus), according to Maslova (exchangeable potassium). The green mass of fallow crops was taken into account by cutting 1 m2 from the plots. The value of indicators of air temperature and precipitation as a whole for the 30-year period of research (in years of different humidification) and in very dry years (HTC according to Selyaninov < 0.4 units) is considered. As a result of research, it was established that the growing season of very dry years was warmer by 6.4 ± 8.7 % with an average air temperature of 20.4 ± 1.7 °C. In the spring, the content of productive moisture in the fallow field variants was 44.7–46.4 mm in the 0–30 layer, 145.0–152.8 mm in the meter layer, and 213.0–225.9 mm in the one-and-a-half-meter layer. In the occupied soil-protective fallow, by autumn there is an increase in nitrate nitrogen (on average for 1993–2022) on an unfertilized background by 65.7 % (+4.4 mg), on a fertilized background by 24.1 % (+2.1 mg). In the green manure fallow, there is a slight (+0.7 mg) increase in the N-NO3 content by autumn and amounted to 10.1 %. The average yield of green mass of Sudanese grass over the years of research was 15.15 t/ha on a fertilized background, and 13.85 t/ha on an unfertilized background. Our experience revealed a high (r = 0.76) relationship between the yield of green mass of Sudanese grass on two backgrounds of soil nutrition with the productive moisture content of a one-and-a-half-meter layer of soil in conjunction with the amount of precipitation in two summer months (July and August).