Аннотация:The study was carried out on the meadow-chestnut soils of farm “OOO Vympel-2002” located in Khasavyurt district of the Republic of Dagestan. The purpose of the research was to examine the effect of varying saturation levels of cereal-grain crop rotations by alfalfa and winter wheat + crop residue natural phytocenosis on the total consumptive water use and the water-use ratio in the Western Caspian region. The main criterion for sustainable yields of winter wheat at 3–4-year repeated sowing is the crop residue natural phytocenosis formed in the second half of summer after harvesting the crop and plowing its biomass for green manure. The study has found that in the cereal-grass crop rotations, alfalfa consumes the largest amount of water for its yield during four years of use. The crop rotation that employs 75 % alfalfa and 25 % of winter wheat+the crop residue natural phytocenosis demonstrates the maximum total consumptive water use of 5000 m3 per 1 ha of rotation area. A larger share of winter wheat + the crop residue natural phytocenosis is crucial for more economical use of water in the crop rotation. The water-use ratio for alfalfa used in monoculture systems was 2660.7; the ratio was 3.7 times lower for winter wheat + the crop residue natural phytocenosis. Crop rotations that used from 75, 50 and 25 % of alfalfa had lower ratios than the monoculture systems (by 38.3, 55.7 and 65.9 %, respectively). The data indicate that the combination of winter wheat + the crop residue natural phytocenosis used for green manure reduce the water needed to obtain yields. The study results should be applied for designing cereal-grass and other types of crop rotations in the region.
