The invention relates to a method for realizing irrigation and fertilizer application integration. The problems of irrigation and fertilizer application integration are effectively solved. The invention adopts the technical scheme that the device comprises a centrifugal sand precipitator, a sand storage and fertilizer storage double-purpose tank and a water pipe, a perpendicular pipeline on the sand storage and fertilizer storage double-purpose tank is communicated with an outlet of the centrifugal sand precipitator through a butterfly valve, a water-in pipe is mounted in the side tangent line direction of the upper part of the centrifugal sand precipitator, an inlet of the centrifugal sand precipitator is communicated with a discharge pipe, a fertilizer liquid return pipe which is perpendicular downwards is arranged on the discharge pipe, a control valve is mounted on the fertilizer liquid return pipe, a lower outlet of the fertilizer liquid return pipe is communicated with the sand storage and fertilizer storage double-purpose tank, a fertilizer filling opening is formed in the upper part of the sand storage and fertilizer storage double-purpose tank, a sand discharging opening with a valve is formed in one end of the sand storage and fertilizer storage double-purpose tank, and the lower part of the sand storage and fertilizer storage double-purpose tank is mounted on a bracket. The method can realize irrigation and fertilizer application integration, simultaneously has the advantages of simple device, small volume, goog convenience for fertilizer application and high fertilizer dissolving efficiency, can be combined with a drop irrigation or jet irrigation system so as to realize the purpose of irrigation and fertilizer application integration, and is suitable for water and fertilizer integral operation under well irrigation conditions.