A method of preparing a fertilizer by feather processing inserts a weighed feather into a reaction container, and then adds caustic potash. Water is then added, and feather disintegration occurs. Phosphoric acid is poured into the mixture, and then the pH is measured—and if necessary improved with phosphoric acid or caustic potash. Epsom salt, vitriol of iron, boric acid, manganic sulphate, zinc sulphate, cuprous sulphate, ammonium molybdate and calcium nitrate are mixed in, and the mixture is partitioned into transportation containers depending on the weight of caustic potash included in the mixture using a drain pump through appropriate filter under constant stirring. The mixture is diluted with water, and the whole mass is perfectly mixed. Humic acids are then mixed into the diluted mixture to form a final keratin fertilizer with humic acid additive in colloid form.