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Pyrophosphate Hydrolysis in Soil as Influenced by Flooding and Fixation
Author(s) -
Racz G. J.,
Savant N. K.
Publication year - 1972
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1972.03615995003600040048x
Subject(s) - pyrophosphate , hydrolysis , chemistry , water content , phosphate , moisture , pyrophosphatase , nuclear chemistry , biochemistry , organic chemistry , geology , enzyme , geotechnical engineering
The rate of hydrolysis of pyrophosphate (K 4 P 2 O 7 ) in a noncalcareous soil maintained at field capacity moisture content or under flooded conditions was determined. Attempts were also made to study the influence of fixation of added pyrophosphate by soil on the rate of pyrophosphate hydrolysis. The initial rate of pyrophosphate hydrolysis was rapid and approximately the same for both flooded soil and soil maintained at field capacity moisture content. The first‐order reaction rate constants, obtained by plotting the log of the concentration of unhydrolyzed pyrophosphate vs. time were 8.14 × 10 ‐4 min ‐1 and 8.37 × 10 ‐4 min ‐1 for soil at field capacity and under flooded conditions, respectively. However, after about 3 days of incubation, flooded soil hydrolyzed pyrophosphate at a relatively greater rate ( k = 2.0 × 10 ‐5 min ‐1 ) than did soil maintained at field capacity ( k = 1.3 × 10 ‐5 min ‐1 ). This difference appeared to be due to an increase in pyrophosphatase activity in the flooded soil. The half‐life of the added pyrophosphate was approximately 2 days. Pyrophosphate adsorbed by an anion exchange resin or fixed by soil hydrolyzed at a slower rate than did pyrophosphate in solution. The ratio of orthophosphate to total phosphate (orthophosphate + pyrophosphate) extracted from phosphated soils by various extractants decreased in the order: water, 0.1 N H 2 SO 4 , and 0.5 N H 2 SO 4 . Water‐soluble or loosely bound pyrophosphate hydrolyzed at a much greater rate than did water‐insoluble or strongly bonded pyrophosphate.