Optimized winter wheat production in Kiev region of Ukraine : a case study on cultivation properties and management focusing on sowing date and nitrogen fertilization

Abstract: Ukraine is the tenth largest wheat producer in the world but average yields are low, about 3 ton ha-1. A better understanding of growth conditions and factors limiting yield is importantin developing strategies to increase grain yield. This Master’s thesis examined the conditions for winter wheat cultivation (Grain Alliance strategy) in Berezan in the Kiev region of northern Ukraine, and the potential to increase crop yields. The wheat cultivation in seven nearby fields in Berezan was compared with one reference field in Uppsala in Sweden. The effect of sowing date was studied by determining plant development and growth in fields with different sowing dates. The effect of fertilization level was also studied in these fields. In the sowing date trials, the factors plants per square meter in late autumn and spring, shoots per plant in late autumn and spring, and plant weight in late autumn were measured. The yield-forming factors ears m-2, kernels per ear, grain size and grain yield were also measured.In the fertilization trials, only grain yield factors were measured. To determine the growing conditions the soil physical properties and water availability were measured. The development of the winter wheat was also simulated by a phenology model with data from local weather stations. The climate in Kiev is 3-5 ˚C warmer than for Uppsala during the period April-August. It results in more rapid plant development in Kiev compared with Uppsala and 4-5 weeks earlier maturity. Precipitation and evapotranspiration are higher in Kiev than in Uppsala. Soil conditions in the Kiev region are favourable, with good soil aeration and low bulk density combined with relatively high amounts of plant-available water. A normal year the amount of precipitation and soil water storage is adequate to supply the wheat with water and avoid drought on both the clay soil in the field in Uppsala and the silty loam in the fields in Kiev. The relatively high temperature and availability of water motivates a cultivation strategy with relatively high ear densities to achieve high yield, as ear size can be reduced by rapid plant development. If winter wheat is sown during the first 2-3 weeks of September there are good opportunities to use relatively low seed rates, as lower plant number can be compensated by tillering. If sowing is postponed quite high seed rates are justified. The early-sown winter wheat in this study had significantly greater biomass and tillering in autumn than late-sown wheat. Plant number was higher for late sowing dates, depending on higher seed rates. Both early- and late-sown wheat survived winter very well. Plant stand density was high in all the seven fields in Berezan, much higher than in the reference field in Uppsala. There was a large reduction of tillers in spring, but final number of ears was still relatively high. As variety and seed rates varied between trials with different sowing dates, it is not possible to claim significant effects of grain yield depending on sowing date. Kernel size was normal but ear size was relatively low, and was the yield factor with highest correlation to yield level in the different fields. Yield level was generally high, even in treatments with low fertilization, and yield increases for high fertilization rates (above 160 kg N ha-1) were relatively low. This indicates quiteextensive mineralization from the soil. No significant difference in yield level was found between wheat fertilized with equal amounts of nitrogen applied in autumn and spring compared with spring only. From a crop perspective, nitrogen from fertilizer must be available at the beginning of stem jointing, when the need is highest. By dividing the fertilization into 2-3 application occasions from early spring to heading, it is possible to adjust the nitrogen rate to development and growth conditions to match stand requirements. The Grain Alliance cultivation strategy gave considerably higher winter wheat yield than the average for the Kiev region, probably due to more intensive management, with the crop not limited by fertilizer deficiency or plant protection problems. Using varieties that combine hardiness and high yield potential, establishing plant stands of sufficient density and performing field operations, for example sowing and fertilization, at the right time are issues to work with for further improvement of winter wheat yield in Ukraine.