Sulfur fertilizer and rhizobia inoculation improved soybean (Glycine max L. Merill) growth performance and N 2 fixation on acidic Nitisols of western Ethiopia

Abstract

Effects of sulfur fertilization and rhizobia inoculation on nodulation, N 2 fixation and growth performance of
soybean on acidic Nitisols of Assosa district, western Ethiopia were assessed under greenhouse condition. The
experiment was consisted of four levels of S (0, 20, 30 and 40 kgha -1 ), three rhizobia strains (MAR-1495, SB-6-1-A 2
and TAL-379) and two soybean varieties (Belessa-95 and Wollo) that was factorial combined in a completely
randomized design with three replications. Nodulation, N 2 fixation and growth performance of soybean were
significantly (P < 0.001) affected by the main effects, two-way and three-way interactions of S fertilizer, rhizobia
strains and variety. Nodule volume, nodule dry weight, shoot dry weight and amount of N 2 fixed were increased
with inoculation of rhizobia strains and S fertilizer application on acid soil. Across S applications, inoculation of
MAR-1495 increased the amount of fixed N by 759% over non-inoculated, showing that it is highly competitive
and efficient strain as compared to others. At 30 kg S ha -1 application, inoculation of MAR-1495 with Belessa-95
and Wollo varieties of soybean have fixed 89.6 and 92.5% more N 2 , respectively over control. Inoculation of
MAR-1495 rhizobia strain with application of 30 kg S ha -1 to Belessa-95 and Wollo varieties of soybean produced
2.5-3 fold increase of soybean shoot dry weight, over the control. The results demonstrate that application of 30
kg S ha -1 and inoculation of MAR-1495 strain were improved N 2 fixation, growth performance and shoot
nutrients uptake of soybean varieties on acidic Nitisols of Assosa area.