Influence of water and nutritional regimes of soil on the productivity of various species of alfalfa

Introduction. The main task of scientific support of fodder production is to expand the range of perennial leguminous crops, especially alfalfa. It is important to determine their productivity under different irrigation and soil nutrition regimes in order to select the most adapted species for use in irrigated agriculture in the Lower Volga region. This will make it possible to produce feeds with high feed values that can fully realize the genetic potential of perennial leguminous grasses. Developments in the cultivation of various types of alfalfa on irrigation, used in fodder production, make it possible to solve the problem of replenishing vegetable protein for agricultural animals while preserving and reproducing soil fertility and the ecological environment.

Object. The object of study is alfalfa, namely the species composition of alfalfa: blue-hybrid alfalfa (control); Yellow alfalfa and variegated alfalfa.

Materials and methods. These studies were carried out in the agro-climatic conditions of the Volgograd region, on light chestnut soils during irrigation at the experimental field of the Irrigated OPH in the period from 2018 to 2022.

Results and conclusions. One of the main reserves for increasing the production of high-quality and high-protein fodder is an increase in the share of leguminous grasses, increasing their yield by expanding the sowing of the most adapted and productive crops and species. As part of the study, the peculiarities of the influence of various irrigation regimes and doses of mineral fertilizers on the growth and development of alfalfa plants were studied. In particular, it was found that when using the NPK2 feed background (full calculated dose of mineral fertilizers) and maintaining the pre-irrigation threshold of soil moisture at the level of 80% of the LV, water consumption for the formation of one ton of green mass of alfalfa is up to 67 m3/t. These indicators were slightly higher for yellow alfalfa – 81 m3/t. A comparative assessment of the yield of the studied species showed that the grass stands of alfalfa of blue and variegated hybrid species were distinguished in terms of productivity. With the creation of optimal growing conditions, maintaining soil moisture at the level of 80% HB (the highest moisture capacity) and improving the nutritional background through the use of fertilizers, these crops were able to provide a yield of green mass in the second year of life at the level of 90.6 t/ha, in the third year - 83.9 t/ha and in the fourth year – 72.1 t/ha. As for yellow alfalfa, its yield of green mass was 69 t/ha in the second year of life and 55.6 t/ha in the third year. Total water consumption (the amount of water used by plants) in grass stands of different ages varied depending on the water regime (irrigation method). It ranged from 60-70% of the lowest moisture capacity (pre-irrigation moisture threshold) of the soil and reached 80% of the LB. In accordance with this, the volume of water used ranged from 5,031 to 5,745 cubic meters per hectare. Positive water and nutritional regimes of the soil significantly affect the growth and development of the root system of alfalfa. Fertilization at a dose of NPK2 and maintaining a soil moisture level of at least 70% of the total moisture capacity contributes to an increase in root weight in the second and third years of plant life, compared to control plots, by 2.7 tons per hectare. On the variants with 80% HB, the increase in root mass was 3.4 t/ha. The main indicator of feed quality in the green mass of alfalfa is the nitrogen content, it varied: from 3.00 in yellow alfalfa to 3.58% in blue and variegated hybrid species. The digestible protein content in the biomass of blue-hybrid and variegated alfalfa was from 147 to 157 g/kg, and in yellow alfalfa 126-132 g. Improved soil water conditions helped to increase grass yields and store more energy. The energy efficiency coefficients in the control variants were up to 2.53 in crops with 60% HB moisture threshold, 2.66 – 70% HB, and 2.71 in the variants with 80% HB. Applying fertilizers with an NPK2 ratio and maintaining a soil moisture threshold of at least 80% of the lowest moisture capacity contributed to an increase in the energy efficiency factor to 4.30%.

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