Wheat growth as affected by inoculation with Azotobacter isolated from different soils

Abstract

Summary Soil samples from different locations in Egypt, Belgium and F.R.G., representing various types of soils, different degrees of fertility and under various standing crops, were used for isolating Azotobacter strains. Twenty-three isolates were obtained and the most active N 2 -fixing strains were studied for their morphological, cultural and physical characteristics. In a greenhouse experiment, the effect of inoculation with three selected Azotobacter strains on the growth of wheat was investigated. Associative symbiosis with plants inoculated with the Egyptian Azotobacter strain revealed the highest values of N 2 -ase activity (up to 114.9 nmoles C 2 H 4 /g/h) followed by those inoculated with the German strain (up to 99.8 nmoles C 2 H 4 /g/h).Lowest rates of acetylene-reducing activity were associated with non-inoculated plants (0.05 to 59.3 nmoles C 2 H 4 /g/h). Plants inoculated with Egyptian Azotobacter strain were significantly longer by 19.5 % and heavier by 15.78 % than the uninoculated correspondings, while no significant differences in plant length and dry mass due to inoculation with the other Azotobacter isolates were observed. Inoculation with any of the tested strains had no significant effect on plant nitrogen content.