OPTIMIZATION OF WINTER WHEAT CULTIVATION UNDER THE RCP8.5 SCENARIO IN THE SOUTHERN STEPPE OF UKRAINE
Abstract
Objective. The study aims to provide a scientific basis and optimize winter wheat cultivation under climate change conditions according to the RCP8.5 scenario in the Southern Steppe of Ukraine, taking into account the rational use of irrigation.
Methodology. The productivity of the crop was assessed using the MODSOL-6 mathematical model adapted to the biological characteristics of winter wheat. The model describes the main processes of yield formation and includes interconnected modules of radiation and thermal regimes, water balance, mineral nutrition, photosynthesis, respiration, growth, and assimilate distribution. Calculations were performed based on decadal meteorological data, considering soil water regime parameters and irrigation characteristics. Numerical experiments were conducted for the baseline (1986–2005) and projected (2031–2050) periods.
Results. The study revealed a shift in the timing of spring vegetation renewal by an average of 9 days later, along with a reduction in the duration of the growing season by approximately 8 days. Significant interannual variability in crop development phases was identified. Climate projections indicate an increase in maximum air temperatures and a decrease in precipitation by about 12%, leading to reduced water availability for crops. Moisture deficit was identified as the main limiting factor affecting leaf area formation, photosynthetic intensity, biomass accumulation, and yield. It was found that only about 30% of years are expected to be favorable for achieving high yields, while in most years drought conditions of varying intensity will prevail, reducing yields to 0.9–3.5 t/ha. Under moderate drought conditions, the maximum biomass increase occurs during the heading phase and reaches about 172 g/m², while with increasing drought intensity it decreases significantly by 1.5–3.5 times. Irrigation modeling demonstrated high efficiency: under moderate drought, irrigation with a rate of 2000 m³/ha ensures yields exceeding 5 t/ha, whereas under severe drought conditions, increasing irrigation rates up to 4000 m³/ha is required to maintain productivity.
Conclusions. Climate change under the RCP8.5 scenario will lead to rising temperatures and decreased water availability, negatively affecting winter wheat productivity. Moisture deficit is identified as the key limiting factor. Optimization of irrigation regimes, taking into account drought intensity, is a crucial measure for stabilizing yields and ensuring efficient cultivation of winter wheat in the Southern Steppe of Ukraine.
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