Development of the soybean root system under the influence of weeds, nitrogen mineral fertilizers and herbicides

Abstract

Aim. The research was to examine the effectiveness of tank mixtures of soil and post-emergence herbicides on the background of mineral and symbiotic nitrogen for implementation of optimal conditions for the functioning and development of the soybean root system. The article presents the results of research on the development of the root system of soybeans under the compatible effect of herbicides and the backgrounds of nitrogen nutrition. Methods. Field research was carried out on the lands of the stationary crop rotation of the Agronomic Research Station of the National University of Life and Environmental Sciences of Ukraine. The cultural plant cultivation technology is generally accepted for the zone. Results. The research results indicate a significant negative impact of crop weed infestation on the formation of the root system of soybeans: the decrease in its raw weight compared to plants in areas free from weeds (with two manual weedings) amounted to 35–44% and the total capacity – by 41–47%. The use of a tank mixture of soil herbicides Zenkor (0.4 l/ha) and Kommand (0.2 l/ha) in the system of protecting soybean crops from weeds resulted in an increase in raw weight and volume of the root system by 1.2–1.5 times with an efficiency close to manual weeding. Pre-sowing seed inoculation had a significant effect on the development of the soybean root system – symbiotic nitrogen increased the raw weight and volume of the root system by 32% and 40% appropriately. The application of the tank mixture Zenkor + Kommand provided the maximum growth upon these biometric indicators within the combined background of mineral and symbiotic nitrogen, where the total volume of the root system increased more than twice. Close correlations were found between both parameters of the soybean root system (r = 0.896). Conclusions. A high correlation dependence (r = 0.785) of soybean productivity on the extent of development of its root system was established. It was noted that while an effective combination of protection and fertilization systems soybeans are able to accumulate in the soil a significant amount of valuable biomass enriched with biological nitrogen, which in field experiments reached 5.6–5.9 t/ha, which was almost three times higher than in the absolute control (2.1 t/ha).