Productivity of sudan grass and sorghum-sudangrass hybrids depending on seeding rates and planting methods in the steppe dryland zone of the Kabardino-Balkarian Republic

. The article contains the results of three-year field research in the steppe dryland zone of the republic, the best options of grass sorghum cultivation, which increase the gross yield of green forage and hay were developed. Optimum planting standards for dry steppe conditions, planting and harvesting methods of Sudan grass and sorghum-Sudangrass hybrids were identified to produce a high, more energy-intensive green and dry forage of the studied crops. The quality and feed qualities of fodder for production and direct feeding to animals are determined. The crop growing time after hay harvest and quantity for feeding after harvesting are given.


Introduction
Feed production is the most labor-intensive and complex process of the agrarian economy. The most important challenge in the intensification of agricultural production in the dryland zone of the Kabardino-Balkarian Republic is the development of a sustainable feed base. Expanding the range of feed crops adapted to specific soil and climatic conditions will better meet the needs of animals for high-quality feed, improve land management and also significantly reduce the adverse climate effects.
In the zone of unstable humidification of the republic, research on promising varieties and hybrids of sorghum crops to identify signs of drought resistance, prematurity, high feed productivity and productive longevity to take full advantage of the favorable bioclimatic potential of local conditions for the production of selected feed products was carried out.
The studied varieties and hybrids have a number of valuable qualities: they grow quickly after cutting or feeding, contrary to other annual feed grasses, which allows them to be more widely used in a green conveyor; with increased yields, they produce high-quality hay, which is superior in protein and fat content to other feed crops, second only to legumes.
The development of the proposed agronomic practices is motivated by the importance of growing feed crops that increase the productivity of the arable land of the dry steppe zone, and by the implementation of feed technology that stabilizes the gross yield in different weather years.
The goal of the research is to improve the elements of grass sorghum cultivation technology by applying optimal timing and seeding rates, planting techniques and the use of varieties and hybrids with different indicators of the biochemical composition of green forage used for the preparation of high-quality and varied feeds.
The task of the field research is to study the growth and development of Sudan grass and sorghum-Sudangrass hybrids with different seeding rates and techniques, to estimate their economic characteristics, and to develop some techniques for the cultivation of Sudan grass and sorghum-Sudangrass hybrids for green forage and hay; to study the varietal differences and chemical composition of studied grasses to identify the most productive varieties and hybrids for production in the unstable humidification zone.
The novelty of the research is that for the first time in the dryland steppe zone of the republic the possibility of obtaining high yields of green and dry forage of grass sorghum with different technological direction of preparation of quality feed is identified. For the first time, on the chernozem soils of the dry steppe zone of the Kabardino-Balkarian Republic, a comprehensive study of various grass sorghum hybrids was performed and their reaction to the implementation of various seeding rates and planting methods, cutting and use regimes were identified.
The research provides science and production with a range of Sudan grass and sorghum-Sudangrass hybrids, optimally selected to the specific soil and climate zone that produces high-quality feeds with high productivity and nutritional value.
The research results were tested and implemented in various farms in the steppe zone of the republic on an area of 85 ha.

Materials and methods
The research was conducted for three years (2015-2017) at the experimental site of the laboratory of technology for the cultivation of field crops of the Institute of Agriculture of the Kabardino-Balkarian Scientific Center of the Russian Academy of Sciences, Tersky district, village Opytnoye Soils are Ciscaucasian carbonate chernozem. The predecessor is winter wheat (2015), grain maize (2016), peas (2017). The humus content in the soil is 3.5%; soil solution reaction is neutral: ph -6.5-7.1; labile phosphorus content -2.0-2.5; exchange potassium -30-40 mg/100g of soil, average annual precipitation is 435 mm with fluctuations from 320 to 545 mm over the studied years, the thickness of the humus horizon is 30-35 cm.  The following seeds were used in the research Sudan grass, Shirokolistnaya variety, originator is the Institute of Agriculture of the Kabardino-Balkarian Scientific Center of the Russian Academy of Sciences Sorghum-Sudangrass hybrid Navigator, originator is Stavropol NAC Sorghum-Sudangrass hybrids, originator is Agroplasma LLC, Krasnodar Sorghum-Sudangrass hybrid Solaris, Agroplasma LLC, Krasnodar Soil preparation technology: autumn plowing at 25-27 cm with application of the main mineral fertilizer -P20K90, presowing cultivation on depth of 8-10 cm; 6-8 days before seeding introduce soil herbicide Doual, Avangard -1,5 l/ha. Solid planting was carried out with C3-3.6 seed, raw planting in 70 cm with SUNP-8 seed with selection of seeding plates -2 mm. During the growing season, 2-3 intercultivations were carried out with a cultivator with the introduction of nitrogen fertilization -60 kg of active agent/ha. The plantings were carried out according to the years of research April 24, 2015, May 02, 2016, May 08, 2017.
Phenological observations were made in terms of age of incineration, tillering tube exit, ear formation, dairy and wax ripeness. Green forage accounting was carried out during the heading of panicles phase of sorghum-Sudan hybrids, and the aftergrass was counted as the maximum crop growth.  Sorghum-Sudangrass Solaris hybrid 1200 650 Scientific research on the study of these crops is carried out in a four-pole crop rotation, the location of plots in the experiment is systematic, and the placement of three tiers is by freights (Table. 2). The experiment is one-factor, the area of the plots is 36 m2, the repetition is three-fold.
Biometric measurements and inventories identified the following characteristics: plant height, tilling capacity, number of plants per square meter, percentage of leaves and stems in total mass. All measurements were made before the green forage of each bite was harvested. There were two hay harvest during the growing season. The first hay harvest of Sudan grass and sorghum-Sudangrass hybrids was carried out on 55-60 days after the sprouting, or 5-6 days before the start of the ear formation, and the second was carried out 40-45 days after the first hay harvest. From each plot, two test sheaves of 5 kg were selected to determine the yield of hay, the structure of the crop (percentage of leaves and stems) and the energy content of green and dry forage.
The Sudan grass Shirokolistnaya variety was used as the standard. Statistical processing of experimental data was performed according to B.A. Dospekhov (1985).

Research results
One of the most significant indicators giving an initial estimate of the studied hybrids is their morphological characteristics. The plant height varies considerably from year to year due to different water availability and growing medium temperature (Table. 3).  On average, in three years of research, plant heights in solid planting in the second hay harvest ranged from 95 to 185cm in the Sudan grass population, with the highest being the sorghum-Sudan Sabantuy hybrid in band planting -174-284 cm.
One of the significant characteristics of plants is tilling capacity. Comparing the number of stems, it should be noted that before the second hay harvest in all variants, this number is greater than in the first harvest (Table.4).  As can be seen from Table 4, over the years of research, the tilling capacity of the investigated plants varies from year to year and from harvest to harvest. Compared to the Sudan grass Shirokolistnaya variety (standard), sorghum-Sudangrass hybrids have a larger tilling capacity of 1.5-2 times, while after the second harvest, according to this indicator the sorghum-Sudangrass Solaris and Sabantuy hybrids can be distinguished -10.0-10.1 respectively.
The quality of the green and dry forage of plants depends on the size of the leaves in total mass and on the genotype of the variety or hybrid, as well as on the weather conditions of plant development. In years with the abundant precipitation, the leafiness of sorghum-Sudangrass hybrids and Sudan grass (in percentage terms) will be lower than in dryland years. In humid years, the plant height reaches 2.5-2.8m, in dryland years -130-170cm, therefore internodes are longer and the number of leaves per plant is equal. Accordingly, the percentage of stems in the total plant mass in a wet year will be higher and leaves will be lower (Table. 5).
As can be seen from Table 5, the lowest green forage yield in years of the research was obtained in 2015 due to soil and air drought, which hindered normal plant development.
It should be noted that the yields of sorghum-Sudangrass hybrids exceed the standard for years of the research and for hat harvests. On average over the years of research, there is an advantage of first hay harvest in all experiments, due to the high temperatures in mid-summer and lack of moisture to fully develop the second hay harvest (Table. 6).  Alyzing the productivity of the investigated options over all years of research, sorghum-Sudangrass hybrids are above the standard for all investigated indicators and can be recommended for cultivation in the dry steppe zone for green forage and hay ( Table 7).
The largest share in the structure of the cost of livestock products is the feed cost. Consequently, the cultivation of sorghum-Sudanicgrass hybrids with lower mass cost is one way of reducing production costs (Table 8). According to the information in Table 8, it can be concluded that sorghum-Sudangrass hybrids exceed the standard in terms of gross green forage charge. The cost of feed units for sorghum-Sudangrass hybrids is lower -125.59-129.34 rubles. compared to the standard -148.80 rubles. The profitability of Sudan grass is 1.41%, while that of sorghum-Sudangrass hybrids is 1.62-1.67%. At the same cost, the net profit increases almost twofold.