| Abstrakt: |
It is often reported that mineralization of less stable forms of organic phosphorus (Po) in Histosols contributes to the P load in drainage waters entering the Water Conservation Areas of the biologically sensitive Everglades wetlands. Consequently, a detailed evaluation of the degree of Postability in Histosols is required, and for this purpose, a Pochemical fractionation scheme was developed. The proposed scheme entailed an acid-alkali sequence of extractions with inclusion of a microbial biomass determination. Experiments conducted to evaluate the validity of the proposed scheme included an assessment of the hydrolysis of selected Pocompounds [p-nitrophenyl phosphate (PNP), D-glucose 6-phosphate (GLU), glycerophosphate (GLY), and inositol hexaphosphate -phytic acid (PA)] in the extractants proposed for the fractionation scheme (0.5 MNaHCO3, 1 MHCl, and 0.5 MNaOH). Minimal hydrolysis (<6%) of all four Pocompounds was caused by NaHCO3extraction, and approximately 40% of the PNP and the GLU was hydrolyzed during extraction with 1 MHCl and 0.5 MNaOH, respectively. However, using the proposed scheme, PNP and GLU would have been removed as readily labile Poby the preceding NaHCO3extraction. Significant effects of various soils extraction conditions on extractable P are also reported and include acid pretreatment and soil:extractant ratio. The proposed scheme was applied to three selected Histosols representing land cultivated for sugar cane, uncultivated land under pasture, and agricultural land converted to a wetland. The distribution of readily labile, moderately labile, and nonlabile pools of organic and inorganic P in the Histosols is discussed in relation to soil and land-use characteristics. |
