A new sand pouch-plant infection technique for enumeration of rhizobia in soil

A sand pouch-plant infection technique for counting most probable numbers of rhizobia in soil is described. Populations of Rhizobium leguminosarum bv. trifoli detected by the plant infection method performed in enclosed glass tubes or in sand pouches did not differ significantly. The described method was used to assess numbers of R. leguminosarum bv. trifoli ( R.l.t .) and bv. viciae ( R.l.v. ) in 20 soils of Poland. Logarithms of the populations of R.l.t. in the tested soils ranged from not detectable level to 4.76 and those of R.l.v. from 2.23 to 5.84 in g1 of soil dry mass. Numbers of R.l.t. were significantly correlated with soil clay, C org, and total N contents but not with the soil pH (in KCI), while numbers of R.l.v. showed significant correlation only with the soil pH.