Effect of root zone temperature on early growth, nodulation and nitrogen fixation in soya beans

SUMMARY Soya-bean plants were grown for 40 days in a range of root temperatures from 10 to 25°C either in a root medium containing N but uninoculated or in a N-free medium but inoculated withRhizobium japonicum. Low root temperature restricted growth in both cases but the plants depending solely on symbiotic N-fixation were much more affected. At 10 CC root temperature plants failed to nodulate but both nodulation and nitrogen fixation increased greatly in the range 15–25°C. It is concluded that soya beans sown in cool soils would benefit from applied nitrogen at sowing time.