Consumption of soil nitrogen by plants in the use of fertilizer, green manure and biopreparation (study with 15n)

In a model experiment on a sod-podzolic medium loamy soil enriched with a stable nitrogen isotope ¹⁵N, the use of soil nitrogen by spring wheat studied when ammonium nitrate was introduced, mustard biomass and seed inoculation with the associated nitrogen fixer Rhizoagrin were introduced. It has been established that plants consume nitrogen primarily from recently applied nitrogen of fertilizer. When making biomass of mustard and inoculating seeds with Rhizoagrin, spring wheat uses soil nitrogen, with the integrated use of these components and applying ammonium nitrate — soil nitrogen and fertilizer. The accumulation of plant biomass predominantly increases from recently applied nitrogen of fertilizer, both separately and when combined with green manure and seed inoculation with a biopreparation and is 14-28% relative to the control without fertilizers. When applying nitrogen fertilizer, as well as when combined with green manure and biopreparation, the concentration of nitrogen in spring wheat increases up to 1.5 times. There is a clear upward trend in the concentration of nitrogen in plants with the addition of mustard biomass and it increases with inoculation of seeds with Rhizoagrin. As a result, the accumulation of total nitrogen in plants increases when nitrogen fertilizer is applied, and the use of mustard biomass and biopreparation increases this indicator by 1.2 times, which is due to the presence of nitrogen compounds available to plants in the nutrient medium. The accumulation in plants of ¹⁵N characterizes the consumption of soil nitrogen by plants, when introducing nitrogen fertilizer, this indicator is less, and using only biomass of mustard and Rhizoagrin is equivalent to control without fertilizers, indicating large amounts of mineralized nitrogen consumption from the soil when using the last two components, and that nitrogen fertilizer is not a factor in the mineralization of soil organic matter. The use of mustard biomass for spring wheat and seed inoculation with Rhizoagrin leads to the consumption of soil nitrogen by plants during the initial growing season.