PRECURSORS AND NUTRITIENT STATUS EFFECT ON THE YIELD OF HARD SPRING WHEAT IN THE URAL ORENBURG ARID STEPPE

The purpose of the research is the yield increase of spring wheat under arid steppe of the Orenburg pre-Urals con-ditions. Stationary long term field experience was laid on the site of the Kuibyshev's experimental production farm located in Orenburg district. Crop rotations and hard spring wheat monocrop have been studied for 30 years. The two-factor experimental design, consisting of four repetitions was developed. The results of long-term stationary studies for 1990-2019 involving five rotations and hard spring wheat monocrop are presented. Weather conditions, the precursor type and nutrient status are the major factors affecting the hard spring wheat yield. The number of hyperarid years when hard spring wheat yield was less than 5 C per 1 ha in the first rotation amounted to 1 year, in the second – 2, in the third and the fourth – 3 years, in the fifth – 5 years. A significant hard spring wheat increase in yield on the basis of fertilized ground over 30 years was noted on weedfree fallow – 6 years, conservation tillage – 10, green manured – 8, winter – 12, corn – 13 and peas – 4 years, monocrop – 10 years. The highest yield of hard spring wheat for five rotations was on weedfree fallow, conservation tillage and green manured areas (average for two nutrient status), respectively, 11.4, 11.4 and 11.6 C per 1 ha, after winter crops – 10.3 C, corn for silage – 9.3 C, peas – 9.0 C and monocrop – 7.7 C per 1 ha. The yield increase from the fertilized ground was obtained within five rotations respectively for these precursors: 0.4, 0.6, 0.6, 1.0, 0.8, 0.3 and 0.9 C from 1 ha. The research was carried out in accordance with the plan for 2020-2021developed by the Federal State Budgetary Scientific Institution «Federal Scientific Center of Biological Systems and Agrotechnologies of the Russian Acade-my of Sciences» (№ 0761-2019-0003).