The invention provides a fertilization system. The fertilization system comprises a fertilizer box, wherein transverse base plates and a longitudinal base plate are arranged at the bottom of the fertilizer box; the transverse base plates are arranged at the left and right sides of the longitudinal base plate; the longitudinal base plate is provided with two longitudinal fertilizer conveying chainswhich are arranged in parallel from left to right, and a rotary axis of each longitudinal fertilizer conveying chain extends frontward and backward; each longitudinal fertilizer conveying chain is provided with longitudinal scraping plates which are arranged from left to right at intervals; rotating directions of the two longitudinal fertilizer conveying chains are opposite and the longitudinal fertilizer conveying chains are used for scraping fertilizer to the transverse base plates at the left and right sides from the longitudinal scraping plates; each transverse base plate is provided withtwo transverse fertilizer conveying chains and rotary axes of the transverse fertilizer conveying chains extend from left to right; each transverse fertilizer conveying chain is provided with transverse scraping plates which are arranged from front to back at intervals; the transverse scraping plates are used for scraping the fertilizer on the transverse base plates to a feeding barrel arranged at the rear side of the fertilizer box and the axis of the feeding barrel extends in the left-right direction; the feeding barrel is internally provided with a fertilizer conveying auger for conveyingthe fertilizer to a discharging opening of the feeding barrel; an organic fertilizer deep application combined working machine comprises the fertilization system.