Features of alfalfa population development under different growing conditions

Purpose. To evaluate the genotypes of alfalfa feed direction under different conditions of moisture and to identify genotypes that would consistently reproduce a high level of economically valuable traits to create new breeding populations. Methods. The research was conducted at the Institute of Irrigated Agriculture of NAAS during 2017‒2020 years in the field for fodder use on two backgrounds of moisture: drip irrigation and natural moisture. In the year of sowing 1‒3 slopes and 3‒4 for the second year of life were carried out by grassland depending on meteorological conditions of the year, genotype, growing conditions. The subject of research were Unitro and Elegy varieties, root system power selections from samples taken in the Askania-Nova Reserve, Rambler, Abayska multi-colored, Siberian 8 and F3‒F5 hybrid populations. Results. Studies have shown that the characteristics of plant height’ and duration of inter-period periods’ are quite variable, they are subject to fluctuations in years of use of grass, slopes and depend on genetic and biological characteristics of alfalfa populations and meteorological conditions. Alfalfa populations differed in the duration of interspecific periods, height and growth intensity in terms of average daily growth depending on the slope and the year of life of the grassland. The duration of inter-period periods, the onset of oblique ripeness of alfalfa depended on the average daily temperature, the duration of sunshine and the length of the day. The calculated correlation coefficients show that the duration of the inter-period periods is strongly inversely related to the average daily temperature (r = -0.93) and weakly dependent on the day length (r = 0.14) and the duration of sunshine for 1 day (r = -0.18), closer to autumn, they decrease, so with each cut the duration of inter-period periods decreases. The longest was the period of germination-beginning of flowering and was 65 days. This is due to the conditions of this period - low average daily temperature (19.2°C), although the duration of sunshine was high and was 751.8 hours, but for the day the sun shone only 11.7 hours. The shortest period was regrowth-beginning of flowering (second slope) and was 43 days at a high average daily temperature (25.7°C) and a long period of sunshine 12.1 hours per day. In the third mowing, the duration of the regrowth period - the last mowing (beginning of budding) was 55 days, but the plants did not reach the mowing maturity, as it was time for the last mowing before the grass enters the winter. During this period, the average daily temperature drops to 19.9°C, day length to 13:32 hours, the duration of sunshine to 9.2 hours per day. The height of plants on the slopes largely depended on meteorological conditions and was maximum in the second slope, reaching 61.3‒67.7 cm. The lowest indicators of the trait were characterized by populations in the first slope with fluctuations from 51.4 to 56.6 cm and the third ‒ 32. 9‒39.7 cm under irrigation. Under conditions of natural moisture, alfalfa plants were significantly inferior in height with fluctuations of 41.1‒48.1 cm in the first slope and high variability from 18.4 to 29.8 cm in the second, with coefficients of variation on slopes V = 4.0 and 10.5, respectively. The largest linear increase in height in the first year of life was characterized by plants in the second slope with an index of 1.43‒1.60 cm/day under irrigation. The average daily increase in the first and third slopes was much lower and was respectively 0.79‒0.87 cm and 0.62‒0.72 cm under irrigation and 0.63‒0.74 cm and 0.43‒0.63 cm in the first and second slopes in conditions of natural moisture. Alfalfa populations did not differ in the length of inter-period periods during the growing season, and they differed mainly in the years of life of grasses. In the grassland of the second year, this difference was observed depending on the slope and meteorological conditions of the year. Thus, in the second year of life with grass from the first slope to the fourth there was an acceleration of the onset of the beginning of flowering phase (oblique maturity). In the first slope it occurred on the 72-nd day, the second ‒ on the 40-th, the third ‒ on the 39-th and the fourth ‒ on the 51-st day. This occurred with a gradual increase in average daily temperature from 12.4°C in the first slope to 23.3 in the third and its decrease to 21.3°C in the fourth slope. In the change in the duration of sunshine, the same pattern is observed: decrease, then a gradual increase with the following decrease: 8.6‒10.5‒11.1‒9.6 hours/day, respectively. The length of the intercostal periods, similar to the first year of life with grass, was inversely related to the average daily temperature (r = -0.982), rainfall (r = -0.644), day length (r = -0.666) and the duration of sunshine in one day (r = -0.961) and the height of plants which largely depended on meteorological conditions, day length (r = 0.778) and precipitation (r = 0.695). Under irrigation conditions, it varied in different populations on slopes from 64.0 to 70.0 cm in the first slope, 68.1–71.4 cm in the second, and acquired a maximum value of 70.6–76.4 cm in the third slope. Subsequently (the fourth slope) the growth of plants slowed down and their height was in the range of 38.7‒49.7 cm. 40.9‒61.5 cm) from slope to slope and only in some genotypes (Elegy, M.g./P.p., L R/H., A.r.d) in the second slope they remain high. A high positive relationship between the average daily linear growth and plant height (r = 0.991). The highest linear growth was characterized by plants in the third slope, ie in July with fluctuations from 1.81 to 1.96 cm per day, smaller growth rates (1.70-1.78 cm / day) differed plants in the second slope under irrigation. Under conditions of natural moisture, the second slope was characterized by intense growth with fluctuations from 1.41 to 1.69 cm per day. Individual populations (Elegy, M.g./ P.P., L R / H., A.r. d.) Maintained high growth or improved its performance in the third slope. In the first slope, alfalfa plants had weak growth with an average daily increase of 0.91-0.97 cm in favorable irrigation conditions and with an increase of 0.84-0.93 cm / day without irrigation, ie they differed slightly on this basis. In the second slope, compared with the first, the plants grew very quickly, their average daily gain ranged from 1.70 to 1.78 cm (under irrigation). Closer to autumn, the growth and development of plants of the fourth slope slowed down, these processes faded, and the average daily gain was only 0.77‒0.97 cm, however, in the conditions of natural moisture alfalfa plants did not form an aboveground mass. Conclusions. Analysis of the results of the research revealed that alfalfa populations differ in height, growth intensity, average daily growth, duration of intermowing periods on slopes, years of grass life and which depend on average daily temperature, duration of sunshine and day length. Valuable genotypes with high rate of linear growth were identified: Elegy variety and populations of M.g./P.p., L R/H., A.r.d. for further selection work.