In order to maintain environmentally friendly agriculture, it is necessary to apply fertilizers based on an assessment of the potential of agricultural land. However, the effects of soil microorganisms based on bioanalysis have not been fully examined, and because of the unexplored nature of the effects, chemical fertilizers are often applied in excess of what is necessary.</p> <p>The purpose of this study is to construct a model that enables evaluation of the nitrogen balance in the process from reservoir to paddy field by adding the effect of the amount of humus-derived nitrogen to the model developed by the authors.</p> <p>For this purpose, the biomass of rice and weeds were detected from hyperspectral images mounted on a UAV, and the growth processes of rice and weeds were grasped with GIS to estimate the amount of nitrogen fixation in rice plants by estimating the biomass of rice and weeds separately.</p> <p>Furthermore, using soil microbial diversity and activity values (BIOTREX), we qualitatively evaluated the contribution of soil microorganisms to nitrogen fixation in paddy rice, built a model that can evaluate the nitrogen cycle derived from organic nitrogen supplied from reservoirs, and estimated the nitrogen balance. The results showed that this model can be used to evaluate the potential of agricultural land as an indicator of the need for fertilizer application.