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United States Department of Agriculture

Agricultural Research Service

Title: Evaluation of Soil Phosphorus Transformations by Sequential Fractionation and Phosphatase Hydrolysis

Authors
item He, Zhongqi
item Griffin, Timothy
item Honeycutt, Charles

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 7, 2004
Publication Date: July 1, 2004
Citation: He, Z., Griffin, T.S., Honeycutt, C.W. Evaluation of soil phosphorus transformations by sequential fractionation and phosphatase hydrolysis. Journal of Environmental Quality. VOL: 169, Pages: 515-527

Interpretive Summary: Phosphorus (P) exists in different forms in soils with different availabilities for plant growth. Increased understanding is needed on the exchange among these P species when manure and fertilizer are added. We used a sequential fractionation procedure coupled with enzymatic hydrolysis to monitor the interchange of several P forms during a laboratory incubation of two Maine soils with fertilizer or animal manure. Soluble inorganic P reached a low and stable level after an initial rapid decrease. Concentrations of other P fractions (species) fluctuated during the incubation period. Furthermore, the fluctuations were observed in complementary patterns of change among several forms. These complementary fluctuations implied an interchange of P species during incubation. The interchange among P fractions is considered to reflect how P dynamics maintain a balance between labile and immobile P in soils.

Technical Abstract: Increased understanding is needed on the exchange among P species when manure and fertilizer are added to soils. Two soils (sandy loam and silt loam) with no P added, with fertilizer P, and with dairy manures were incubated at 22 oC for up to 108 days. Sequential fractionation with H2O, 0.5 M NaHCO3, and 0.1 M NaOH and phosphatase hydrolysis were used to monitor changes in inorganic P and enzymatically hydrolysable and nonhydrolysable organic P during the incubation period. Similar patterns of P dynamics were observed in the two soils. Added inorganic P from either chemical fertilizer or animal manure was found mainly in the NaHCO3 and NaOH fractions. Changes in H2O, NaHCO3, and NaOH extractable P were similar for P fertilizer amended soils and unamended soils, indicating soil properties played a major role in controlling P dynamics. In the H2O fraction, inorganic P attained a low and stable level after an initial rapid decrease. Concentrations of other P fractions (species) fluctuated during the incubation period. Furthermore, the fluctuations were observed in complementary patterns between inorganic P in the NaHCO3 and NaOH fractions, as well as between labile P (inorganic and hydrolysable organic) and nonhydrolysable organic P in the NaOH fraction. These complementary fluctuations implied an interchange of P species during incubation. The interchange among P fractions is considered to reflect how P dynamics maintain a balance between labile and immobile P in soils.

Last Modified: 4/19/2014
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