Effect of Soil surface Soil Management Practices on Microflora in Volcanic Ash Soils of Citrus Orchard

This study was conducted to investigate the effect of different surface soil management practices on soil microflora in volcanic ash soils of citrus orchard. Soil samples were collected from citrus orchards of clean cultivation, grass sod, and grass mulch system in May and September 1997. Soil chemical properties, populations of various microorganisms, enzyme activities, microbial biomass C were analyzed. Average soil pH were 4.7, and average nitrogen and organic matter contents were 6 and $140.2g\;kg^{-1}$, respectively. Aerobic bacteria were distributed at $26,2-47.3{\times}10^6cfu\;g^{-1}$ level. Among the aerobic bacteria Pseudomonas spp., Rhizobium spp., and thermophilic Bacillus spp. were dominant in most of the investigated orchard soils. Density of actinomycetes were low at $1.8-84.6{\times}10^5cfu\;g^{-1}$ level. Fungi were distributed at $26.4-182.1{\times}10^5cfu\;g^{-1}$ level and the density was higher in grass mulch and sward sites. In september, phosphomonoesterase activity was high at $239.6{\mu}g\;PNP\;g\;soil^{-1}\;h^{-1}$ in clean cultivated citrus orchards. Soil cellulase activity were higher at $602.6{\mu}g\;GE\;g\;soil^{-1}$\;24\;h^{-1}$ in grass sward cultivation than any other soil management practices. Soil microbial biomass C was higher in grass mulch cultivated orchards.

화산회토 감귤원의 표토관리방법이 토양 미생물상에 미치는 영향

화산회토 노지 감글원에서 청경, 초생, 부초재배 등의 표토관리 방법이 토양의 미생물밀도, 효소활성 및 microbial biomass C에 미치는 영향을 조사하였다. 1997년에 개화기인 5월과 과실비대기인 9월에 청경재배, 초생재배, 부초재배 감귤원 각각 10개소에서 토양을 채취하여 조사한 결과는 다음과 같다. 표토관리방법에 따른 토양의 화학성 차이는 없었으며 pH는 평균 4.7로 낮았다. 유기물과 질소 함량은 평균값으로 각각 140.2 및 $6g\;kg^{-1}$이었으나 조사지점에 따라 다양하였다. 감귤원 토양에서 호기성 세균은 $26,2-47.3{\times}10^6cfu\;g^{-1}$ 수준의 분포를 나타냈으며 호기성 세균속 중에는 Pseudomoras spp., 고온성 Bacillus spp., Rhizobium spp. 등이 우점하는 경향이었다. 방선균은 $1.8-84.6{\times}10^5cfu\;g^{-1}$ 수준으로 분포를 하였고 개화기에 밀도가 높았다. 사상균은 $26.4-182.1{\times}10^5cfu\;g^{-1}$ 수준의 분포를 나타냈으며 초생재배와 부초재배에서 많았다. 과실비대기에 토양 인산효소활성은 청경재배에서 $239.6{\mu}g\;PNP\;g\;soil^{-1}\;h^{-1}$, 토양 cellulase 활성은 초생재배에서 $602.6{\mu}g\;GE\;g\;soil^{-1}$\;24\;h^{-1}$로 높았다. Microbial biomass C는 부초재배에서 $256.3mg\;C\;kg\;soil^{-1}$로 가장 높았다.