Integrated fertilization method for recommending the rationing of the dose X (dX) of nitrogenous fertilizers to the dose of nitrogen (dN) to be applied to agronomic field crops established on soil-borne aerial cellulosic crop residues comprising the following steps; determination of the quantity of soil-borne aerial cellulosic crop residues; representative sampling of these aerial cellulosic crop residues covering the arable soil surface in question; the determination of the nitrogen content of these soil-borne aerial cellulosic crop residues (Nrcs); obtaining the value RVN = soil-borne aerial cellusosic crop residues RCS / nitrogen content Nrcs of these soil-borne crop residues RCS, or gain = agronomic yield of the previous culture RDT / nitrogen N content Nrcs of these same soil-borne crop residues RCS; determining the rMS value empirically using univariate relationships with respect to the agronomic yield of the previous crop, rMS being equal to the ratio of the soil-borne aerial cellulosic crop residues to post-harvest underground crop residues from root biomass; the empirical determination using standard curves of the value rNS as a function of RVN, rNS being equal to the ratio of the nitrogen content of these soil-borne aerial cellulosic crop residues relative to the nitrogen content of post-harvest underground crop residues from root biomass (Nrac), i.e. between the aforesaid N contents of aboveground (aerial) biomass (Nrcs) and that of underground biomass (nitrogen content of underground crop residue from root biomass, Nrac), this variable being obtained empirically using univariate relationships with respect to RVN; calculating the index iVAZ = [rMS - rNS] or iVAZ = [rMS / rNS]; depending on the quantity of soil-borne aerial cellulosic crop residues, obtaining a critical value for iVAZ (iVAZc), iVAZc being calculated from the index iVAZ = [rMS - rNS] compared to the potential non-symbiotic nitrogen fixation in the soil (pAZB); if the calculated iVAZ is lower than this critical value, rationing of the dose X is not recommended, and finally; the application of the dose of nitrogen (dN) to agronomic field crop on the basis of this recommended level of rationing of the dose X; the iVAZc thus calculated from the index iVAZ = [rMS - rNS] relative to the potential non-symbiotic dinitrogen fixation in the soil (pAZB) being expressed, (i) as the ratio between the nitrogen contents of the aforesaid underground root-derived crop residues and soil-borne aerial cellulosic crop residues (pAZB1) - the relative paucity in nitrogen of soil-borne aerial cellulosic crop residues being favourable for the non-symbiotic in situ dinitrogen fixation, and (ii) as a ratio between dinitrogen fixation (AZBrcs) rates within soil-borne aerial cellulosic crop residues and post-harvest underground root-derived crop residues (AZBrac), i.e. pAZB2, or even more formally; pAZB 1 = nitrogen N content of underground root-derived crop residues Nrac / Nrcs ⁢ π ratio without units, pAZB 2 = dinitrogen fixation AZBrcs within soil-borne aerial cellulosic crop residues RCS / dinitrogen fixation AZBrac within post-harvest underground root-derived crop residues RAC ratio without units, the value of the critical iVAZ (iVAZc), being defined by the intersection of these two functions, i.e. pAZB1 = pAZB2, and this for each level of agronomic yield of the previous field crop and/or of soil-borne aerial cellulosic crop residues thus returned to the soil surface. determination of the quantity of soil-borne aerial cellulosic crop residues; representative sampling of these aerial cellulosic crop residues covering the arable soil surface in question; the determination of the nitrogen content of these soil-borne aerial cellulosic crop residues (Nrcs); obtaining the value RVN = soil-borne aerial cellusosic crop residues RCS / nitrogen content Nrcs of these soil-borne crop residues RCS, or gain = agronomic yield of the previous culture RDT / nitrogen N content Nrcs of these same soil-borne crop residues RCS; determining the rMS value empirically using univariate relationships with respect to the agronomic yield of the previous crop, rMS being equal to the ratio of the soil-borne aerial cellulosic crop residues to post-harvest underground crop residues from root biomass; the empirical determination using standard curves of the value rNS as a function of RVN, rNS being equal to the ratio of the nitrogen content of these soil-borne aerial cellulosic crop residues relative to the nitrogen content of post-harvest underground crop residues from root biomass (Nrac), i.e. between the aforesaid N contents of aboveground (aerial) biomass (Nrcs) and that of underground biomass (nitrogen content of underground crop residue from root biomass, Nrac), this variable being obtained empirically using univariate relationships with respect to RVN; calculating the index iVAZ = [rMS - rNS] or iVAZ = [rMS / rNS]; depending on the quantity of soil-borne aerial cellulosic crop residues, obtaining a critical value for iVAZ (iVAZc), iVAZc being calculated from the index iVAZ = [rMS - rNS] compared to the potential non-symbiotic nitrogen fixation in the soil (pAZB); if the calculated iVAZ is lower than this critical value, rationing of the dose X is not recommended, and finally; the application of the dose of nitrogen (dN) to agronomic field crop on the basis of this recommended level of rationing of the dose X;