The formation of green mass yield of alfalfa under different doses and periods of mineral fertilizers application in the conditions of the Right Bank Forest Steppe of Ukraine

Abstract

Doses of fertilizers and timing of their application had an effect on the growth, development, survival of alfalfa and on the energy efficiency of its cultivation. The best survival of alfalfa was observed in the options where P120K120 was applied twice during the growing season. At the same time, survival was within the range of 72.0-74.1% for the first cut, 66.2-68.4% for the second cut, and 46.5-47.2 % for the third cut. The lowest survival of alfalfa plants was observed on the variant without fertilizers and, respectively, on the cut, it was 69.5, 63.5 and 41.9 %. The largest leaf surface area of alfalfa was observed in the variant with P120K120 application in autumn and spring and was 129,000 m2 /ha, which exceeded the control by 2.3 times. On the variants with introduction of alfalfa P120K120 and P60K60 during the growing season, the yield of green mass increased by 1.9 times compared to the control. The highest green mass yield of alfalfa was obtained with double application of P120К120 – 54.2 t/ha, which significantly exceeded the control. Portion application of fertilizers (P60K60 in autumn and P60K60 in spring) has no significant advantage over P120K120 fertilization in spring or autumn (the yield was 39.9, 40.4 and 39.2 t/ha, respectively). The green mass yield of alfalfa was unevenly distributed according to the terms of mowing. On average, according to the experiment, the first cut gave 35.9 % of green mass, the second cut – 39.3%, and the third – only 24.8%. The use of mineral fertilizers in the dose of P60K60 led to an increase in the total energy consumption of alfalfa cultivation by 1.89 GJ/ha, or by 6.71%, compared to the control. When applying P120K120, the costs increased by 4.39 GJ/ha, or by 15.59%, compared to the control. Mineral fertilizers application under alfalfa helped to increase the energy coefficient. The introduction of P60K60 led to an increase in the energy coefficient by 11.7%, compared to the control, P120K120 – by 31.9%, P60K60 in autumn P120K120 in spring – by 39.3%, and P120K120 in autumn and P120K120 in spring – by 56.2%. It was established by calculations that mineral fertilizers contributed to the reduction of the energy intensity of 1 ton of fodder units. So, if the energy intensity of 1 ton of feed units was 1.06 GJ in the version without fertilizers, then the introduction of P60K60 led to a decrease in this indicator by 10%, P120K120 by 24.0%, P60K60 in the fall, P120K120 in the spring by – 28.1%, and P120K120 in autumn and P120K120 in spring – by 36.1%. Key words: alfalfa, fertilizer doses, time of application, yield of green mass, alfalfa slopes, economic efficiency, plant density, growing season, plant survival.