Dissolution of phosphorus fertilizers of differing solubility in peat soil: a field experiment on a drained pine bog

A 2-yr field trial was conducted on a drained pine bog to measure the disso lution of five phosphorus (P) fertilizers of differing solubility. The rate of fertilizer dissolution was measured using a sequential fractionation wh ich involved pre-extraction with 0.5 M NaCl/TEA followed by I M NaOH and a mixed acid (HNO3 + HCl + H2SO4) digestion. About 56% of Siilinjarvi apatite , a hard magmatic rock phosphate, dissolved over the 2 yrs. For a commercia l P+K fertilizer manufactured from Siilinjarvi apatite and KCI (water-solub le P < 0.1%), the corresponding value was 44%. For Moroccan phosphate rock, and a commercial fertilizer manufactured from Moroccan phosphate rock and KCl (water-soluble P = 15.8%), the dissolution was about 44% and 58%, respe ctively. For superphosphate (water-soluble P = 79%), the corresponding valu e was 93%.