EFFICIENT FIELD CROP ROTATIONS IN THE DRY STEPPE ZONE OF THE LOWER VOLGA REGION
The studies were carried out on the experimental field of the Nizhne-Volzhsky Research Institute of Agriculture in 2014-2016 years. The goal is to develop promising field biologized crop rotations that ensure the preservation and reproduction of fertility of light chestnut soils on the basis of renewable bioresources, high yield of grain in the dry steppe zone of the Lower Volga region. We studied the field crop rotation: 1) bare fallow - winter wheat - sorghum for grain - oats (control); 2) green-manure fallow (winter rye as green manure) - winter wheat - sorghum for grain - oats; 3) green-manure fallow (false flax as green manure) - winter wheat - sorghum for grain - chickpea - safflower - oats; 4) field pea - winter wheat - chickpea - safflower - pea - sorghum for grain - chickpea - oats. The soil is light chestnuts. In control, the straw and leaf-stem stuff was removed from the field. In other rotations all non-manufactured part was embedded in the upper layer of soil. The highest positive balance of organic matter was noted in the four-field crop rotation with winter rye as green manure (+3.33 t/ha). Positive nitrogen balance was provided only in four- and six-course biologic crop rotations, respectively +40.6 and +16.9 kg/ha. Positive balance of potassium was observed in all biologized crop rotations, except for control, where it was negative. Negative balance of phosphorus was noted in all variants of the experiment. The most favorable humus balance was observed in grain cultivated and fallow row-crop four-course crop rotation with winter rye on the green manure (+0.16 t/ha). The highest grain yield per 1 hectare of crop rotation area was obtained in the same crop rotation - 1.87 t/ha. The greatest economic effect was achieved in eight-course and four-course biologized crop rotations, where the level of profitability is 79 and 78%, respectively. The area of application of the recommendations is dry steppe zone of the Lower Volga region.