Effects of value-added phosphate fertilizers on transformation of inorganic phosphorus in calcareous soils

In this study, the value-added phosphate fertilizers were made by combining humic acid, alginic acid and glantamic acid with mono-ammonium phosphate (MAP), and the composition and transformation of inorganic phosphorus in calcareous soil were studied under laboratory incubation condition. The results show that the soil available phosphorus contents are significantly increased and soil pH is significantly decreased after 180 days incubation with the application of phosphate fertilizers, whether they are MAP or the value-added phosphate fertilizers. The soil available phosphorus contents are increased by 34.6 mg/kg to 41.92 mg/kg and soil pH decreased by 0.23 to 0.36 with the application of the value-added phosphate fertilizers. The value-added phosphate fertilizers decrease the P fixation obviously. Compared to the MAP treatment, the P fixation percentages of humic acid phosphate fertilizer, alginic acid phosphate fertilizers and glantamic acid fertilizers are decreased by 7.32%, 7.13% and 11.99%, respectively, and the value-added phosphate fertilizers increase the contents of Ca2-P, Ca8-P and Al-P and retard the transformation from Al-P to Fe-P.