| Summary: | 碩士 === 國立臺灣大學 === 農業化學研究所 === 87 === Soils closed to the corn or rice rhizosphere were collected from an experimental field in Taiwan Agricultural Research Institute, from September 1997 to July 1998. In which two enzymes related to carbon-cycling (cellulase and β-glucosidase) and two enzymes related to sulfur-cycling (arylsulfatase and rhodanese) were analyzed to examine the effects of different fertilization management on the enzyme activities. The seven fertilization management were (1) CK, (2) Chem-N, (3) Comp, (4) Comp + 1/3N, (5) Comp + 2/3N, (6) GM + 1/3N, and (7) Peat +1/3N. The effects of different fertilization management on the thermal stability of enzymes in field-moist and air-dried soils were also examined. Finally, the content of soil sulfate, total phosphorous, and inorganic phosphorous were analyzed to study the relationship of soil enzyme activities and the content of soil inorganic nutrients.
The results from the corn system and rice system indicated that these two systems had the same management effects on the soil enzyme activities. Incorporation of organic amendments increased the soil arylsulfatase activity except for the Comp + 2/3N and GM + 1/3N treatments. Comp treatment had the highest arylsulfatase activity. The chemical fertilizer treatment reduced the arylsulfatase activity. Compared with the CK treatment, the soil rhodanese activity was not increased by any other fertilization treatment. On the contrary, the soil cellulase and β-glucosidase activities were increased by fertilization treatment. The three treatments amended with compost had the highest soil cellulase and β-glucosidase activities. The statistic test of management×stage interaction during the corn growing periods showed that arylsulfatase activity was effected by the soil sulfate content.
The results of heating the field-moist soil samples at tasseling stage of corn showed that only soil rhodanese maintained higher thermal stability (7.2-14 % of original activity). The other three enzymes maintained very low thermal stability (0-8.1 %). Compared with the field-moist soils, air-dried soil enzymes were more resistant to heating. The air-dried soil arylsulfatase and rhodanese activities had no significant management×heating interaction, i.e., no treatment had higher thermal stability. Comp and GM + 1/3N treatments increased the soil cellulase and β-glucosidase thermal stability (p < 0.1).
Measurement of the field-moist soil sulfate content at knee-height and harvesting stage of corn indicated that the sulfate in superphosphate inhibited the soil arylsulfatase activity. The regression of different management''s soil sulfate content and arylsulfatase activities showed that the transformation of soil sulfate ester in Comp and Peat + 1/3N treatments were more moderate than in the GM + 1/3N treatment. In the case of phosphorous, after corn planting and rice transplanting, we obtained significant positive correlation between the content of soil total phosphorous or inorganic phosphorous and soil arylsulfatase, cellulase, or β-glcosidase activities. The cellulase and β-glucosidase activities had very significant (p < 0.001) correlation with the phosphorous contents. Rhodanese activity had negative correlation with the phosphorous contents.
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