P avAllability of water-soluble phosphate fertilizer decreased with time in calcareous soil.During a short time(two months),about two thirds of fertilizer turned into inextractable phosphates with 0.5mo1/L NaHC0₃.The fractions of the phosphates were primarily Ca-P,Al-P and Fe-P.Under conditions of corn growth,22.6-27.8% of fertilizer-P was transformed into Ca₂-P,27.5-30.6% into Ca₈-P,9.1-10.0% into Al-P,10.5-15.6% into Fe-P,while 11.3-18.8% was absorbed by the corn plants.Ca₂-P,Ca₈-P,Al-P and Fe-P phosphates in calcareous soil were avAllable for corn.The DWPP (dry weight of corn plant produced by 100mg supplied phosphorus of the four phosphate-types) in a decreasing order:Ca₂-P>Al-P>Ca₈-P>Fe-P.Ca₁₀-P phosphase was unavAllable for corn.