The work purpose was the justification of opti-mum water mode of the soil providing stable obtain-ing productivity in combination with introduction of settlement doses of mineral fertilizers not lower than 1.5 t/hectare of grain. The results of the four years' researches connected with justification of the combination of the water mode of the soil and the application of fertilizers providing stable receiving on the irrigated lands of the Middle Amur are pre-sented in the study: 1.0; 1.5 and 2.0 t/hectare of grain of buckwheat of summer terms of crops. It was established that without irrigation and fertilizers in different years its productivity changed within 0.55-0.63 t/hectare. For the guaranteed obtaining productivity of 1.0 t/hectare on crops of buckwheat it is necessary to support water mode with humidity of the soil in a layer of 0.4 m not lower than 60 % of the smallest moisture capacity (SMC); 1.5 t/hectare - 70 % of SMC in combination with introduction of N40P80K20 and 2.0 t/hectare - 80 % of SMC and introduction of N50P100K30 of kg/hectare of active ingredient. For each option of water mode total wa-ter consumption, the regulations of watering, and also reference indicators of the characteristic of the course of formation of the agrocenosis providing the way to receiving the planned buckwheat crop is defined: the density of standing of plants, stalk height, the maximum area of leaves, photosynthetic potential, absolute weight is 1000 seeds. Due to the drowning of part of plants in option of formation of 2.0 t/hectare of grain and decrease as in growing this crop it is recommended to be guided by carry-ing out watering in preirrigation humidity of the soil of 70 % of SMC.