Simulation of lucerne green mass productivity on non-irrigated and irrigated lands under climatic changes

Goal. TTo evaluate the results of mathematical modeling of the productivity of crops and yield of green mass of lucerne on southern heavy-clay chornozem according to the RCP8.5 scenario of climatic changes in non-irrigated and irrigated conditions of the Southern Steppe of Ukraine. Methods. The RCP8.5 scenario of climate change — to predict the water-thermal regime, mathematical modeling — to conduct numerical calculations, and analysis of the research results. Results. They expect that during the research period in 2031 – 2050 on non-irrigated lands of the Southern Steppe in the I hay crop period, there will be good agro-climatic conditions that will contribute to the formation of green mass yields at the level of 27.9 t/ha. In the II hay crop period, due to an increase in air temperature (average maximum temperature — 30.3 versus 21.8 °C), and a decrease in precipitation (65 versus 113 mm), the yield will be 16.4 tons/ha. Very hot conditions (an increase in the average maximum temperature to 34.6 °C, a decrease in precipitation to 20 mm) of the III hay crop period will contribute to a yield of only 2.3 tons/ha. On irrigated lands, with the maintenance of productive moisture reserves at the level of 75% of NV in the soil layer of 0 – 100 cm thick, the yield in all 3 periods will increase: 1st hay crop — up to 30.0 t/ha, 2nd — up to 32.8 t/ha, 3rd — up to 10.6 t/ha. Conclusions. In the Southern Steppe of Ukraine, on the southern chornozem under the RCP8.5 scenario of climate change in the agro-climatic conditions of the spring-summer growing season of lucerne on non-irrigated lands, there will be losses of the yield of green mass because of severe drought in the II inter-mowing period and very severe drought in the III inter-mowing period (50% and 78% respectively). Growing lucerne on irrigated lands will increase the yield of green mass by 1.5 times; in general, for vegetation, it will be 73.4 tons/ha.