Evaluation of Root Noduletingrhizobial Strains for Fababean Crop at Kulumsa, Southeastern Highlands of Ethiopia

The response of fababean to seed inoculation with ninestrains of Rhizobium leguminosarum along with recommended phosphorous from TSP fertilizer was examined in field experiments at a total of five sites from 2013 to 2015 at Kulumsa in the southeastern highlands of Ethiopia. Full (18– 46 kg N–P2O5 ha-1) and half doses nitrogen and phosphorous from inorganic source (DAP), and no input at all were also included in the treatments. The experiment was laid out in randomized complete block design with three replications. The result of 2013 trial showed seed inoculation with root noduleting rhizobium strains significantly improved the productivity of fababean. The highest grain yields of fababean were obtained from seed inoculations withstrainsEAL-110, FB-Murd, 1035 and 1018 along with recommended phosphorous from TSP. Equivalent yields were also obtained from the applications of full and half doses of recommended nitrogen and phosphorous from DAP. Seed inoculation withstrainFB-140 and FB-9 along with recommended phosphorous from TSP also resulted in statistically similar biomass yields. Seed inoculations with strain FB-Murd, FB-140, FB-9 and FB-4 along with recommended phosphorous from TSP resulted in statistically the highest biomass yields in 2014. There were no significant yield and yield components responses of fababean to both seed inoculations with root noduleting rhizobium strains and applications of inorganic fertilizers in 2014 and 2015. Previous studies in Munesa district in the southeastern highlands of Ethiopia already confirmed that seed inoculations with strains EAL-110, 1018 and 1035 were efficient in fixing nitrogen. Promising results were obtained from inoculation of fababean seeds with strains FB-Murd, FB-140, FB-9 and FB-4.

deficiency is also another significant factor that reduces the nodulation since both effective rhizobium bacteria and the crop require in larger quantity [6]. The objective of this study was, therefore, to identify effective strains that increase production and productivity of fababean crop and enhance the soil fertility for subsequent cereal crops.

Description of the Study Area
This study was conducted at Kulumsa on-station and on the surrounding farmers' fields for three consecutive years. Kulumsa and its surrounding receive a mean annual rainfall of 811mm. The mean maximum and minimum temperatures of the area are 24.5°C and 10.5°C, respectively. The soil of the area is characterized by verticluvisol with a clay loam soil texture.

Experimental Set-up and Procedure
The experiment included nine strains of Rhizobium leguminosarum (FB-4, FB-7, FB-9, FB-17, FB-140, FB-Murd, 1018, 1038 and EAL-110) along with full dose of recommended phosphorous (46 kg P 2 O 5 ha -1 ) from TSP fertilizer. Full (18-46 kg N-P 2 O 5 ha -1 ) and half (9-23 kg N-P 2 O 5 ha -1 ) doses nitrogen and phosphorous from inorganic source (DAP), and no input at all were also included in the treatments. The experiment was laid out in randomized complete block design with three replications. Planting of trials were conducted during the fourth week of June in all years with fababean (Tumsa variety) at a seed rate of 150 kg ha -1 at a total of seven sites.

Data Collection and Analysis
The agronomic parameters collected (determined) were stand count, tillers per plant, plant height, spike per m -2 , grain and aboveground total biomass yields, hectoliter and thousand kernel weights of fababean. When the crop was physiologically mature, harvesting was done from a net plot area of 4 m 2 (2 m by 2 m) by hand for yield determination. The harvested samples were subjected to air drying to constant moisture content, threshed manually, cleaned and the grain weight recorded. The weighed samples adjusted to 10% moisture content and converted into kg ha -1 for statistical analysis.
Two sites in the first year were dropped due to poor crop performance and five sites were considered for harvesting, data analysis and interpretation.
All yield and yield components data were combined across sites and subjected to analysis of variance using the general linear model procedure (Proc GLM) of SAS statistical package version 9.0 [7]. The significance of differences among treatment means was compared using Duncan multiple range test at the 5% level of probability.

Results and Discussion
The results of three years trials were inconsistent; hence, separate analysis of variances was conducted. The result of 2013 cropping season indicated that fababean yield and yield components were significantly affected by seed inoculation with root noduleting rhizobium strains and applications of inorganic fertilizers (Table   1). However, fababean crop did not respond to both seed inoculation with root noduleting rhizobium strains and applications of inorganic fertilizers in 2014 (except for harvest index and biomass yield) and 2015 cropping seasons (Table 2&3).    The result of the 2013 trial showed that seed inoculation with root noduleting rhizobium strains improved the yields of fababean (Table 4). The highest grain yield of fababean (5209 kg ha -1 ) was obtained from seed inoculation with strain EAL-110 along with ap-ping seasons ( Table 5). The non-significant yield responses might be attributed to the relatively high soil fertility status of the experi-

Conclusion
The Previous studies conducted at Munesa district in the southeastern highlands of Ethiopia already confirmed that seed inoculation with strains EAL-110, 1018 and 1035 along with application of full dose of recommended phosphorous from TSP were effective in fixing of nitrogen with fababean crop [10]. The result of 2013 and the implication from 2014 showed that FB-Murd along with applica-tion of full dose of recommended phosphorous from TSP was promising. In order to make the final conclusion, seed inoculation with strainsFB-9 and FB-4 need to be studied further under different soil types and agroecologies. It is recommended to check the viability of strains just prior to planting.