Solubility of native and added soil phosphorus

Abstract

Native and added phosphorus were extracted from several soils samples with 0.05 N H2S0(4), 0.05 N HC1 + 0.025 N H2S0(4), 0.05 N H2S0(4) + 0.025 N NH4F and CH3COOH 0.10 N solutions, in conjunction with three solution : soil ratio, 5 :100, 10:100 and 20:100 keeping constant the lenght of extraction period for 15 minutes. The soil solution ratio showed a marked influence on the phosphorus extraction, that is, there was a decrease of 50% or more, when the ratio varied from 5 :100 to 20:100. The 0.05 N H2S0(4) + 0.025 N NH4F solution extracted more phosphorus than 0.05 N H2S0(4) and 0.05 HC1 + 0.025 N H2S0(4) solutions from the soil with pH 5.70 or less and with more than 17.0% of Fe(2)0(3)+A2O3. This point out that the anion F- allows a better phosphorus extraction from those soils. The 0.10 N CH3COOH solution extracted phosphorus only from the soil with pH = 7.10 and with 5.6% of Fe(2)0(3) + Al(2)0(3), showing that acetic acid solution did not evtract native and added phosphorus from acid soils and with a high content of iron and or aluminium oxides.