Effects of Salt-induced Stress on the Fluctuation and Rhizosphere Colonization of Soil Microorganisms

염류(鹽類)의 스트레스가 주요(主要) 토양미생물(土壤微生物)의 변동(變動) 및 근권정착성(根圈定着性)에 미치는 영향(影響)

A study was carried out to evaluate the effect of different salts and their Quantities on the fluctuation and rhizosphere colonization of soil microorganisms. The results obtained are as follows. The electrical conductivities(ECs) of $KNO_3$, $K_2HPO_4$, KCl and $K_2SO_4$ showed negative correlations to the number of gram positive bacteria and gram negative bacteria : the number of bacteria was significantly decreased in the KCl or $KNO_3$ treated group compared to the $K_2HPO_4$ or $K_2SO_4$ treated group. The highest microorganism density of gram negative bacteria, gram positive bacteria and Fusarium sp. in balanced salts-treated soil was observed at $0.5dS\;m^{-1}$, $2.1dS\;m^{-1}$ and $8.0dS\;m^{-1}$ of EC, respectively. The ratio of bacteria to fungi ratio in balanced salts-treated soil substantially decreased as the EC of soil increased. Ten and thirty days after soil treatment with balanced salts, the ratio of bacteria to fungi decreased to 757-1571 and 89-215, respectively. Root colonization density of Fluorescent Pseudomonas in cucumber and tomato significantly decreased as the EC of soil increased, whereas that of Fusarium sp. increased.

본 시험은 염류의 종류와 처리함량에 따른 작물근권 생태계의 미생물상 변동과 근권정착성을 구명하고자 하였다. 토양처리 염류($KNO_3$, $K_2HPO_4$, KCl, $K_2SO_4$)의 염농도(EC)와 포자형성세균, 그람음성세균수는 부의 상관관계를 보였으며, $K_2HPO_4$, $K_2SO_4$보다 KCl, $KNO_3$ 처리구에서 균수가 급격히 감소하였다. 균형염 처리토양의 미생물 밀도는 탄소원 첨가의 경우 그람음성세균은 EC $0.5dS\;m^{-1}$, 포자형성균은 EC $2.1dS\;m^{-1}$, 사상균 및 Fusarium sp.은 EC $8.0dS\;m^{-1}$에서 최대의 균수를 보였다. 균형염 처리토양의 Bacteria/Fungi 율은 염농도가 높아질수록 현저히 감소하며 토양처리 10일 경과후 757~1571, 30일 경과 후 89~215로 현저하게 낮아졌다. 오이, 토마토 근권 미생물의 뿌리정착밀도는 토양의 염농도가 높아질수록 형광성 Pseudomonas sp.은 현저하게 감소하였으나 병원성 Fusarium sp.은 증가하였다.