EFFECTS OF SOIL COMPACTION ON THE MICROBIAL-POPULATIONS OF MELON AND MAIZE RHIZOPLANE

Effects of soil compaction on the microbial populations of melon and m aize rhizoplane were investigated in quantity and quality. The numbers of culturable bacteria and fluorescent pseudomonads on the rhizoplane were higher when plants were grown in more compacted soil and the rel ative increase was larger in fluorescent pseudomonads. Total bacterial counts, however, did not appear to be affected by soil compaction, re sulting in the increase in the culturable bacteria among total counts in more compacted soil. The determination of extracellular enzymatic p roperties (pectinase, alpha-glucosidase, beta-glucosidase and alpha-ga lactosidase) of each 100 isolates from bulk soil and root samples sugg ested that the microbial populations on the rhizoplane, especially whe n plants were grown in highly, compacted soil, were composed of high r atios of bacteria with abilities to utilize root exudates efficiently. The microbial community structure estimated from the colony forming c urves of bulk soil and root samples suggested that the microbial popul ations on the rhizoplane, especially when plants were grown in compact ed soil, were likely to be composed of more r-strategists which were d efined as those who formed colonies within 2 days.