Effects of excessive soil temperatures in the symbiosis of soybean (Glycine max L. Merril)

Abstract

In three greenhouse experiments the effects of high soil temperature on nodulation and nitrogen fixation were studied on four soybean varieties. Daily maximal temperatures above 33°C reduced nodule initiation and nodule efficiency while nodule growth was less affected. Rhizobium strains occurring naturally in the soil seemed more tolerant to excessive soil temperature than selected strains. Soybean varieties and Rhizobium strains varied in their tolerance to excessive soil temperatures.