Nutrient Release Characteristics And Manurial Effects Of Big Spherical Coated Controlled-Release Fertilizer

In order to study the nutrient release characteristics of coated big spherical controlled-release compound fertilizers, an experiment in which major factors containing coating thickness, adequate amount of degradable starch added to coating materials, temperature and sphere diameter affecting the differential nutrient release from coated big spherical fertilizer was performed in water. The results showed that release rates of nitrogen and potassium were significantly faster than that of phosphorus. Thinning coating thickness or adding adequate starch increased the nutrient release rates. Raising the temperature from40℃to60℃significantly increased the nutrient release rates, but there was no significant difference for the nutrient release rates when raising temperature from25℃to40℃. Increasing sphere diameter of the fertilizers did not significantly change the nutrient release rates, moreover, did save the coating materials and decrease the production cost.Through soil columns leaching test, the leaching characteristics of big spherical coated controlled-release fertilizer used for fruit trees and the effects of fertilizer treatments on pH value, electrical conductivity of leachate and nutrients such as nitrogen, phosphorus, potassium and magnesium in leachate were studied. The results showed that the leachate pH of big spherical coated controlled-release fertilizer was significantly higher than that of the soluble fertilizer, but there was no significant difference with no fertilizer control and the other two kinds of controlled-release fertilizer treatments. In the whole leaching process, the electrical conductivity and the nutrients contents in leachate of inorganic nitrogen, water soluble phosphorus and water soluble potassium treated by the big spherical coated controlled-release fertilizer were significantly lower than that of soluble fertilizer at the earlier fractions of leaching, and were significantly higher than that of the other two kinds of controlled-release fertilizers in most fractions of leaching especially at the later fractions. The nutrients loss by leaching of inorganic nitrogen, water soluble phosphorus and water soluble potassium were38.72%,1.91%and24.76%, respectively. According to the above conclusions, the big spherical coated controlled-release fertilizer could decrease nutrients leaching loss, and reduce pollution of groundwater.Application of big spherical coated controlled-release fertilizer could improve the content of chlorophyll a in peach leaves in fruit mature stage and extend the physiological process of nutrient transfer storage in the peach tree. The leachate pH value with big spherical coated controlled-release fertilizer was close to neutral but higer than equivalent common fertilizer significantly, and the leachate electrical conductivity with big spherical coated controlled-release fertilizer was reduced by54%than equivalent common fertilizer significantly. For the big spherical coated controlled-release fertilizer treatment, the available phosphorus content of potted soils were101.99mg/kg and77.49mg/kg in branch pump stage and furit mature stage respectively, and the available potassium content of potted soils were175,26mg/kg and121.31mg/kg in branch pump stage and furit mature stage respectively. The available phosphorus and available potassium content treated by big spherical coated controlled-release fertilizer from branch pump stage to furit matrue stage respectively decreased by24%and31%, significantly lower than the common fertilizer treatment which respectively decreased by62%and64%. The leaching loss of nitrogen, phosphorus and potassium with big spherical coated controlled-release fertilizer was reduced by35%,64%and74%than equivalent common fertilizer significantly, respectively.