Effect of high doses of superphosphate on the group and fractional composition of phosphates containing in dark gray forest soil

Abstract. The purpose of the work was to study effect high doses superphosphate on yield forage beans and composition phosphates in dark gray forest soil. Research methods. studies were carried out a microfield experiment. Doses are calculated taking into account increase phosphorus content from medium very high. total determined after calcining soil, mineral group natural state soil an extract 0.2n sulfuric acid, fractional by method S. Chang M. Jackson. Results. High (the degree supply is high) without introduction nitrogen potassium fertilizers significantly reduce productivity beans. optimal mobile increased (101–150 mg/kg according Kirsanov). double phosphate relation original make up 77 %, organophosphates – 22.8–23.3 %. Analysis showed that use water-soluble increases amount all fractions. fraction loosely bound 5 (medium supply) 14 at level. From phosphates, calcium occupy 20–23 aluminum 12.5–14.9 share ferrophosphates practically does not change with dose 25.3–25.7 poorly soluble most significant: supply, equal 438 mg / kg 529 this 37.1–38.8 % phosphates. scientific novelty lies calculation fertilizer, stepwise transition one provision another, high, This approach calculating makes it possible differentiate nitrogen-potassium fertilizers.