Statement of the problem. Alfalfa is one of the most valuable crops to supply high-quality livestock forage. In the arid conditions of the country one of the important tasks is to determine the elements of resource-saving technologies, aimed at efficient usage of moisture by plants, in particular the cultivation of this crop for seeds.
The aim of our work was to study the water regime of the soil under crops of alfalfa of different mowing for seeds production (first, after-grass, and intermediate) in the southern Steppe and to determine of more resource efficient.
For intermediate mowing of grass the option of cutting plants for green fodder for 3-4 days prior to the beginning of budding and get ting the seeds after the next growing of alfalfa is chosen.
The results of the research. The largest consumtion of moisture during the growing season from soil to biomass formation was for the first mowing of grass for seeds: from the arable layer was spent 366, and from the meter layer – 1078 m3/ha. The given index for intermediate sowing was 81 and 78, and the second – 117 and 334 m3/ha less. Dry matter, including the seeds of alfalfa of the first mowing, is formed by 51.6% due to precipitation and 48.4% of soil moisture. Another pattern in the formation of above-ground biomass was observed during the intermediate and second sowing: the expenditure of water from the soil were significantly greater in percentage terms – 59,8% and 58.6% of, respectively, whereas rainfall in the total consumption was only 40,2 and 41.4%.
The total water consumption of plants in agrophitocenosis for the first mowing within 2225 m3/ha), for intermediate mowing – 1673 and after-grass mowing – 1269 m3/ha. Decline of this mowings indicator with is connected the less formation of biomass in the intermediate and after-grass sowing comparing with the first mowing.
Transpiration ratio was 800 for the first one, 740 – for intermediate and 858 for the second mowing for seeds. For the formation of 1 kg of seeds was spent 1441±308 m3 of moisture by controlled plants. On the intermediate sowing the coefficient of water consumption decreased by 1.6 times (up to 914±214 m3/d) compared with the first mowing. During intermediate and second sowing significantly more seeds of alfalfa were formed 1 m3 in precipitation and soil moisture (116 and 130 g/m3, respectively) comparing with the first mowing – 73 g/m3. In intermediate mowing of aboveground biomass accumulated less in comparison with the first mowing, so seeds per unit of moisture had formed more in all years of the study. The main expenditure of water on the formation of seeds in the intermediate (293 g/m3) and after-grass (316 g/m3) occur due to soil moisture. Much less seeds formed in these mowings due to precipitation (195 and 230 g/m3), whereas in the first mowings of the ratio of expenditures of soil water and rainfall is almost the same – 153 and 147 g/m3, respectively.
The conclusions. Analysis of the obtained data on water mode in the soil when growing alfalfa on unirrigated lands gives the basis to indicate whether the use of intermediate mowings for yield of seed crops in the southern Ukraine. At intermediate mowing a more economical use of moisture by alfalfa of seed purpose compared with the first and second mowings.
L. Antipova. The water mode of alfalfa fields seeds for cultivated.
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