Rhizobium numbers in the rhizospheres of red clover and paspalum in relation to soil treatment and the numbers of bacteria and fungi

Abstract

Estimates of the numbers of fungi, bacteria, and clover rhizobia in the rhizospheres of red clover and paspalum grown in a krasnozem (pH 4.8) have shown that the stimulation of fungi and general soil bacteria is limited to that soil in immediate contact with the roots. The stimulation of rhizobia by the red clover roots appears to be more extensive, with high numbers occurring in the soil, even 10–20 mn from the roots. Paspalum roots increased the numbers of rhizobia in the soil immediately surrounding the roots, but to a lesser degree than did clover. Amelioration of the soil increased the levels of bacteria and fungi in the soil and in the rhizosphere, with spectacular increases in the numbers of rhizobia in the rhizosphere of red clover.