| Summary: | 碩士 === 國立臺灣大學 === 農業化學研究所 === 91 === Two sampling methods (immersing and scraping methods) of rhizosphere enzymes were examined to establish a suitable one for studying the rhizosphere enzyme activities under a long-term maize-rice rotational cropping system. An experimental field was selected to study the effects of fertilization management on five rhizosphere soil enzyme (-glucosidase, urease, acid phosphatase, arylsulfatase, and dehydrogenase) activities, and to study the relationships between the enzyme activities of rhizosphere soils and the enzyme activities, soil chemical and biological properties of bulk soils. The results obtained could further provide references to understand agricultural soil ecosystem and the way to increase soil productivity. The maize-rice royational cropping system was initiated in the experimental field since August 1995. The experimental design was a Randomized Complete Block Design with four replications and seven fertilization managements, including: (1) Check (CK), (2) Chemical N (Chem), (3) Hog manure compost (Comp), (4) Comp + 1/3 chemical N, (5) Compost + 2/3 chemical N (Comp +2/3 N), (6) Green manure + 1/3 chemical N, (7) Peat + 1/3 chemical N. This study staeted from August 2001, only managements 1, 2, 3, and 5 mentioned above were selected.
The results showed that the immersing method consumed less time and higher enzyme activities than the scraping method, but there was no significant difference between them for the coefficients of variation. Hence, the immersing method is a better sampling method of rhizosphere soils for assaying enzyme activities. Among the maize crop growing stages, the activities of -glucosidase and acid phosphatase in rhizosphere soils were highest in the knee-high stage, and those of urease and arlysulfatase in rhizosphere soils were highest in the tasseling stage; among the rice crop growing stages, the activities of -glucosidase and urease in rhizosphere soils were highest in the heading stage, that of dehydrogenase in rhizosphere soils were highest in the active tillering stage, and those of acid phosphatase and arylsulfatase in rhizosphere soils were highest in the harvesting stage. The results also showed that Comp and Comp + 2/3 N managements generally significantly increased the activities of rhizosphere soil enzymes more than other two managements in maize and paddy field. The activities of -glucosidase, urease, acid phosphatase, arylsulfatase, and dehydrogenase in rhizosphere soil were significant positive correlations with -glucosidase activity and organic matter content, urease activity, acid phosphatase activity, sulfate content, and dehydrogenase activity and microbial biomass nitrogen content of bulk soil in maize field, respectively. The activities of -glucosidase, and dehydrogenase in rhizosphere soil were significant positive correlations with organic matter content, and microbial biomass nitrogen content of bulk soil in paddy field, respectively. Urease activity in rhizosphere soils were significant negative correlations with ammonium-nitrogen, nitrate-nitrogen, and inorganic nitrogen content of bulk soil in paddy field.
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