A Sequential Extraction Procedure with Concentrated Sulfuric Acid and Dilute Base for Soil Organic Phosphorus

Abstract

A total soil organic P (TPo) method that retains the relative ease of the dry combustion method and still preserves essentially all organic P in the extract would be desirable. A sequential extraction procedure for TPo with concentrated sulfuric acid and dilute base was therefore developed to meet these objectives. The method was based on the high efficiency of Po extracted from soils by the heat of solution created by addition of water to concentrated H2SO4. In this step of the procedure, 79% of the total Po was extracted. The acidic soil residue was next treated with NaOH to complete the extraction of Po. The sum of the acid‐ and base‐extractable Po gave a measure of the total soil Po. The method did not hydrolyze or only minimally hydrolyzed Po substrates added to test soils. The proposed procedure was compared with the Mehta extraction method, and with an ignition method developed by Saunders and Williams. In a test of 12 different soils (prairie to highly weathered) the proposed procedure extracted an average of 4% more Po than did the Mehta, and 17% less Po than the Saunders and Williams procedures. The proposed procedure is more rapid than either of the other procedures, and is equally precise. The ease with which the proposed method can be performed as stated, or performed in combination with the high temperature base extraction of the Mehta procedure, makes it ideal for routine laboratory use, especially when the nature of the Po compounds also is being investigated.

Formas de fósforo no solo sob leguminosas florestais, floresta secundária e pastagem no Norte Fluminense

“…O Po total foi obtido por meio do método de extração seqüencial (Bowman, 1989), e o Po lábil, pelo método de extração com NaHCO 3 0,5 mol L -1 (Bowman & Cole, 1978). O Pi foi determinado após clarificação dos extratos com carvão ativo (Guerra et al, 1996).…”

Nutrient constraints to tropical agroecosystem productivity in long‐term degrading soils

“…Organic matter was first precipitated by acidification in the bicarbonate and the NaOH extracts before P i determination (Tiessen & Moir, 1993). Total P in the bicarbonate, the NaOH and the HCl extracts was measured after digestion of extracts with potassium persulfate (Bowman, 1989). Organic P was calculated as the difference between total P and P i in the bicarbonate, NaOH and hot HCl extracts.…”

Phosphorus transformation in poultry litter and litter-treated Oxisol of Brazil assessed by 31P-NMR and wet chemical fractionation

“…The WC litter and litter-treated soil were incubated for 43 days and sampled after 0, 15, 22, 29, 36, and 43 days to monitor the P transformation kinetics. The collected samples were chemically fractionated (Bowman, 1989) into inorganic (Pi) and organic phosphorus (Po) fractions. The change in Pi and Po was calculated as the difference in P forms during the incubation period and the rate of P mineralization was calculated from the percentage increase in Pi during incubation per unit of Po.…”

“…The chemical fractionation of litter using Bowman's fractionation scheme (Bowman, 1989) revealed that the concentration of Pi was higher in the RH litter and lowest in the CH litter, but did not differ from Pi in the WC and CC litters (Table 3). The same pattern was observed for the Po concentration.…”

“…Using a similar fractionation procedure, Sharpley & Moyer (2000) however reported the contribution of a Po fraction of 9 % of total P in a litter consisting of pine bark (three lots raised, 1.31 birds m -2 ). In the last decade, several methods have been used to characterize the different P forms in soils and animal manures (Hedley et al, 1982;Bowman, 1989;Dou et al, 2000;Sharpley & Moyer, 2000).These differences might be due to the distinct methods used in the assessment of P fractions (Koopmans et al, 2003), as well as the bird's diet, origin and management of the litters (Maguire et al, 2006).…”