摘要或動機

1.Purpose of the research We observed frequent application of chemical pesticides and herbicides at the pear orchards near our school. Our concerning questions are the influences of agricultural chemicals on soil ecosystem which may be slowly deteriorating. There are many other orchards where the farmers are practicing environmentally-friendly agriculture using organic fertilizers such as composed manure instead of sycnthetic fertilizers. The purpose of this research is to examine chemical and mocrobiological quality of the orchard soil. We report biological control of pear disease using antagonistic microorganisms and suggest improvement of soil quality as a result of nature friendly agricultural practice. 2.Procedures and Data Two orchards were selected: Conventional fertilizers and chemical pesticide application farm; Environmentally friendly farm using organic plant manure and biological control of disease. Several different aspects of soil micro-flora, indicator microorganisms, physiological characteristics of pear fruit, residues of synthetic chemicals in the soil, soil chemical properties were examined. We could observe that use of organic manure and biological control agents for disease control by indigenous microorganisms improved biological and chemical quality of the orchard soil. Results are summarized as follow: A. Microbial diversity could be observed in organic farming orchard soil. Among 42 fungal genus, 7 species of penicillium including P. decumns, 3 Alternaria species, 4 Fusarium species including Fusarium graminearum, 6 Aspergillus species including Aspergillus niger were identified. In case of bacteria, 59 samples were isolated and 17 genus including Cystophaga johsonae were identified. B. Beneficial indigenous bacteria having several biological functions were isolated: Enterobacter intermedium produces organic acid therefore this bacterium can solubilize insoluble phosphate. Several Pseudomonas species were isolated. These bacteria produce iron chelating compound under iron limited environments and can control plant disease. Interestingly, we could find indigenous biocontrol agent Hypocrea vinosa which can effectively control black star disease on pear surface. C. We have formulated ten different microbial-pesticides using several combinations of indigeous microorganisms such as Hypocrea vinosa, Trichoderma atroviride, Rhizopus microsporus etc. These microbial-pesticides could inhibit 100% of black star disease on pear surface which showed similar inhibition effect as commercial pesticides indicate that these microbial-pesticides may replace synthetic chemicals in the near furture. 3.Conclusions Our research demonstrates the eco-friendly organic farming system could improve soil eco-system of pear orchard, where no synthetic fertilizers and pesticides are applied. As a result of manure application, the soil chemical properties are more stable and microbiological flora was more diverse. Use of microbial and bio-pesticide resulted in strong inhibition of black-star disease incidence on pear surface. We suggest that eco-friendly farming systems are needed to diminish environmental pollution in soil and water caused by frequent and abundant use of agricultural chemicals.