Soybean varietal response to irrigation and fertilization in the Lower Volga region

The research was conducted to study the responsiveness of soybean cultivars with different maturation periods to irrigation water and fertilizer and to select cultivars that provide high yields while saving water and agrochemical resources. The method of laying the field experiment was applied (B.A. Dospekhov, 1979). We used different cultivars of RRIIA breeding and doses of fertilizers designed to obtain a yield of 2.5 to 4.5 t/ha of grain. The plot area was 35 m². The factorial experiment was conducted with four replications. An irrigation regime of 80 % FMC was achieved by watering 0.4 m layer of soil until budding phase and during ripening period — full ripeness. During the generative periods of development of agrophytocenosis (budding — filling of seeds in beans), the moisture inflow into the soil was increased to a depth of 0.6 m. The share of irrigation water increased significantly in years with hydrothermal coefficient GTC₀₂ (2020) — up to 76.5 % — compared to more favorable years with GTC₀₅ (2019). Early maturing cultivars were characterized by the lowest consumption of irrigation water per season: VNIIOZ 86 (3138…4014 m³/ha) and Volgogradka 2 (3653…4381 m³/ha), compared to mid-season cultivars VNIIOZ 31 and Volgogradka 3 (4078…5027 m³/ha). Cv. Volgogradka 2 had the greatest responsiveness to irrigation water — 3.57 t/ha and the lowest water consumption coefficient — 1136 m³/t of grain compared to other cultivars with indicators of 2.81…3.74 t/ha; 1235…1297 m³/t, respectively. For the first time, under irrigation in the Lower Volga region, the technology for obtaining high levels of grain yield of 2.97…4.27 t/ha was improved through the use of genotype of cultivar of regional breeding (Volgogradka 2, Volgogradka 3) and improved mineral nutrition of plants based on a programmed yield (2.5…4.5 t/ha).