| Summary: | 碩士 === 臺灣大學 === 農業化學研究所 === 98 === Green onion (Allium fistulosum L.) is an important cash crop in Taiwan. Monocropping of green onion is a common agricultural practice. Howerer, monocropping often resulted in lowing soil quality and increasing pest and disease incidences as well as aridification of the soil. Application of organic matter or lime can alleviate the problem resulting from monocropping. There are studies about the monocropping of green onion on the soil chemical properties. However, the effects of monocropping on soil biochemical properties and microbial properties are need to study. The objective of the present study was to evaluate the effect of different fertilization managements on green onion growth and soil chemical properties, enzyme activities, and microbial communities. The experiment was conducted in a green house in National Taiwan University. The soil used was taken from an green onion cultivation farm land in I-lan. There were six treatments (1) no fertilizer application for control, (CK) (2) applying chemical fertilizer treatment (1.56-0.65-0.65 g pot-1)（N-P2O5-K2O）, (CF) (3) applying organic fertilizer with the same amount N as CF, (1X) (4) applying organic fertilizer with the two-fold amount N as CF, (2X) (5) applying 50% of chemical fertilizer and along with 50% of organic fertilizer mixed, (CO) (6) applying organic fertilizer (same as 1X) and tea seed pomace, (TO). All treatments were replicated six times and arranged in completely radom design. No fertilizer was applied in the second crop. The plants were harvested after 100 days after of transplanting. Soils of root zone were taken after haversting the crops. The plants were subjected chemical analysis for the nutrient contents and the soils was subjected the analysis for chemical properties, enzyme activies, microbial structure using phospholipid fatty acid (PLFA). The results indicated the soil pH, organic matter content, enzyme activities and microbial biomass of chemical fertilizer treated plots were lower than those of organic matter treated plots. The fungi/bacteria ratio and specific microbial stress indicatior of the CF treatment were higher than those of organc fertilizer treatments. The actinomyces/bacteria ratio of the soil of TO treatment was higher than that of organic fertilizer treatment. All enzyme activities studied showed a significant linear correlation with the organic matter cotent of the soil. There were significant correlations between the activities of different soil enzymes. There was a significant difference between the soil pH, enzyme activities, and microbial biomass of treatments between the first and the second crop. After harvesting of the second crop, the Gram positive/negative bacteria ratio of the soil of the 1X, 2X and CF treatment were significantly lower than the soil of the same treatment of the first crop. The Gram positive/negative bacteria ratio of the soil of the CF treatment decreased 26% in the second crop compared with the first crop. After harvesting of the second crop, the actinomyces/bacteria ratio of the soil of the CF treatment was significantly lower than the soil of the same treatment of the first crop. There were significant correlations between green onion biomass, soil biochemical properties, microbial biomass and PLFA. There were significant correlations between green onion biomass, and soil biochemical properties, microbial biomass, and PLFA, respectively. The biomass of second crop green onion deceased 35% compared with the first crop. In conclusion, application of chemical fertilizer may result in a decrease in soil quality and green onion yield. Organic fertilizer resulted in maintaining the soil pH, increasing enzyme activities and microbial biomass of the soil that cultivated green onion, as well as reducing the stress conditions for microbes.
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