Soil phosphorus fractions in sandy soils amended with cattle manure for long periods

摘要: Phosphorus fractions were determined in soil samples from areas fertilized or not with farmyard cattle manure (FYM) and of FYM used the semi-arid region Paraiba state, Brazil. Soil taken 0-20; 20-40 40-60 cm layers 18 cultivated areas, which, according to interviews farmers, had been treated 12 20 t ha-1 annually, for past 2 40 years. also collected four unfertilized pasture as controls. was sequentially extracted water (Pw), resin (Pres), NaHCO3 (Pibic Pobic), NaOH (Pihid Pohid), H2SO4 (Pacid) and, finally, by digestion H2SO4/H2O2 (Presd). Nine water, resin, Mehlich-1, H2SO4, H2SO4/H2O2, sequentially, extracts analyzed P. The sampled homogeneous, sandy P-deficient soils; increases total P (Pt) above mean value control (up 274 mg kg-1 0-20 layer most P-enriched samples) therefore attributed applications, which only external input region. Regression analysis study relationship between Pt. Pacid fraction, related Ca-P forms, showed greatest (p < 0.01) a result rising 8.4 non-fertilized sample 43.8 highest Pt content. sum Pw, Pres Pibic, considered labile P, comparable Pacid, while Pihid smallest increase due applications. Organic forms increased, more so fraction Pohid, less labile, than one, Pobic. residual practically half Pt, independently value. Increases organic justified high average concentration Pw (36 %), (34 Pohid (30 %) FYM. Significant changes proportion among indicated downward movement forms.