THE PREDECESSORS INFLUENCE ON THE SPRING WHEAT YIELD IN THE REPUBLIC OF TUVA

The purpose of research is to study the influence of predecessors on increasing the yield and grain quality of spring wheat in arid steppe conditions. Research was carried out since 2002 in the experimental fields of the Tuva Research Institute of Agriculture on dark chestnut medium loamy soils with a humus content of 3.37 %. In the arid conditions of the dry steppe of the Republic of Tyva, the advantage of pure fallow was noted in comparison with repeated crops. Thus, the yield of spring wheat above 2.00 t/ha in pure fallow was 26.7 %, and in re-seeding only 6.7 %. The yield of spring wheat from 0.51 to 1.00 t/ha in pure fallow was noted only once, and in re-croppings five times during the entire research period. Sowing spring wheat in pure fallow over all years of research showed an increase in wheat yield on average 1.4 times compared to repeated sowings. It was revealed that in the conditions of the steppe zone of the republic it is advisable to cultivate spring wheat after such predecessors as peas, potatoes and green manure, which provide an increase in wheat yield by 1.24–2.08 t/ha compared to its continuous cultivation. It is noted that the use of mineral fertilizer changes the effect of predecessors, transferring the worst predecessors to the category of the best. Thus, applying mineral fertilizer to repeated crops of wheat can increase the yield of spring wheat by 12.5 %. The highest productivity of spring wheat from the use of mineral fertilizer is observed in pure fallow, where the increase was 16.9 %.