Factors affecting enzymic and nonenzymic hydrolysis of trimetaphosphate in soils
1985
BUSMAN, L. M. | TABATABAI, M. A.
The hydrolysis of trimetaphosphate (TMP) in soils is catalyzed by the enzyme trimetaphosphatase and by nonenzymic constituents of soils. Statistical analyses indicate that the activity of trimetaphosphatase in 28 surface soils examined is correlated with the organic C, total N, and clay content. The rate of nonenzymic hydrolysis of TMP is correlated with soil pH, organic C, total N, water-extractable Ca and Mg, and clay content. Trimetaphosphatase activity generally decreased with organic C content and with depth in soil profiles. The nonenzymic hydrolysis of TMP increased with depth in soil profiles to a depth of 30 to 75 cm, but decreased with depth below 75 cm. The vegetation cover had little effect on the nonenzymic hydrolysis of TMP, but soils under soybeans had significantly lower trimetaphosphatase activities than corresponding soils under grass. Treatment of soils with formaldehyde, EDTA, mercuric chloride, sodium nitrite, ascorbic acid, and orthophosphate inhibited trimetaphosphatase activity in soils. Trimetaphosphatase activity was noncompetitively inhibited by EDTA, PO4], and analogues of PO4] (MoO4], WO4], VO], AsO4], and B4O7]). Treatment of soils with formaldehyde, EDTA, ascorbic acid, orthophosphate, pyrophosphate, or triphosphate decreased the nonenzymic hydrolysis of TMP, whereas treatment of soils with K2SO4, NH4Cl, CaCl2, and MgCl2 increased the rate of nonenzymic hydrolysis of TMP. Storing field-moist soil samples at 5°C was an effective method for preserving the trimetaphosphatase activity of soils for at least 3 mo. Storage of air-dried soil samples for 3 mo retained from 58 to 102% of the initial trimetaphosphatase activity of freshly sampled field-moist soils.
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