Productivity of crop rotations depending on the degree of saturation of alfalfa and winter wheat with stubble natural phytocenosis in the Western Caspian region

Abstract

The photosynthetic activity of alfalfa and winter wheat with PEF in crop rotations was studied at Vympel-2002 LLC in the Khasavyurt district of the Republic of Dagestan. The soil of the experimental plot is meadow-chestnut, heavy loamy, in the arable layer contains humus 2.77%, K2O - 32.8 and P2O5-2.21 mg / 100 g, its density is 1.24 g / cm3, the lowest moisture capacity of the soil layer - 0.6 m, in which the humidity was studied to determine the timing and norms of irrigation - 29.2%. The studies were carried out in three grain-grass crop rotations saturated with alfalfa and winter wheat with PEF from 25 to 75%, and their monocultures. The formation of PEF for green manure after harvesting winter wheat in the second half of summer, in terms of its influence on the photosynthetic activity of crops of subsequent winter wheat in the crop rotation, made it possible to achieve the same high indicators as after such a most valuable predecessor for it as alfalfa. Despite the fact that the latter, due to its multi-cutting, alfalfa forms 2.8 times more leaf surface area during the growing season, in terms of photosynthetic potential of crops (PPP) and net photosynthesis productivity (NPP) it is inferior to winter wheat with PEF in 1.6 and 6.2 times, respectively. PEF phytomass used for green fertilizer, smoothing out the negative impact of its long-term re-sowing on the phytosanitary state of the soil and the yield of the leading grain crop, can become the most acceptable way out of the situation when, due to the current structure of sown areas, winter wheat occupies 60- 80% of the crop rotation area and it has to be placed in the same field for 3-5 years without a change.