N2Africa - Putting nitrogen fixation to work for smallholder farmers in Africa Symbiotic effectiveness of rhizobia and its effect on smallholder soyabean productivity in Zimbabwe *Tatenda T Kainga 1, Sheunesu Mpepereki 1, Paramu L Mafongoya 1,Talkmore Mombeyarara 2, Name Organisation 1 University of Zimbabwe Address: P O Box MP167, Mt Pleasant, Harare, Zimbabwe Phone: , , Name Organization 2 International Centre For Tropical Agriculture Address: P O Box MP228 Mt Pleasant, Harare, Zimbabwe Phone: Materials and methods Study site description and Experimental design and treatments  The study was carried out in three districts of Zimbabwe, namely Mudzi, Mhondoro and Murewa which fall in three agro-ecological regions (II, III and IV) differentiated by rainfall distribution and temperature patterns (Fig 1) Fig 1:Map showing the study area, i.e. the districts and wards in which field trials where carried out in Zimbabwe  experimental design -Randomized Complete Block Design with two factors-variety and strain with three replicates  2 sites 25*40 m 2 where selected from each district based on willingness of farmer, availability of land, soil type, cropping history and management of land  Each site- 3 blocks-16 sub-plots 3*4 m 2 /block, 7 strains used to inoculate 2 varieties- SC Saga (specific) and TGX (promiscuous)  Basal Compound L (5% N, 18% P 2 O 5, 10%K 2 O and 0.25% Boron) at 150Kg/ha at planting  Descriptive Statistics on biomass and grain yield were done using Genstat version 14 Background The authors are grateful to CIAT-N2Africa for the funding and to AGRITEX for their collaboration References Abaidoo, R.C., H.H. Keyser, P.W. Singleton, K.E. Dashiell and N. Sanginga. (2007) Population size, distribution and symbiotic characteristics of indigenous Bradyrhizobium spp. that nodulate TGx soyabean genotypes in Africa. Mpepereki, S Technology adoption by smallholder farmers: lessons from the soyabean research/promotion program in Zimbabwe Giller, K.E., Murwira, M.S., Dhliwayo, D.K.C., Mafongoya, P.L and Mpepereki S Soyabeans and sustainable agriculture in Southern Africa Acknowledgements Results and Discussion Fig 2: soyabean grain yield for each of the three agro-ecological zones (a) shows grain yield attained from SC Saga a local hybrid specific variety (b) shows grain yield attained from TGX an imported hybrid promiscuous variety from Malawi Fig 3: biomass yield attained at 50% flowering when biomass production as well as nitrogen fixation is at its peek (a) shows biomass yield attained by SC Saga and (b) shows biomass yield attained by TGX variety Fig 4: Photo and (a) shows roots of two plants, the one on the left was inoculated with MAR1305 and the one on the right was inoculated with MAR1515 (b) shows a table with the mean scores attained after nodule scoring of the strains There was a significant interaction between the agro- ecological region, strain and variety. There was a significant grain and biomass yield difference between the strains (p natural region4>natural region3 in relation to the fertility of the fields used. Conclusion Varieties inoculated with MAR 1305 &MAR 1306 perform better than those inoculated with MAR 1491 in terms of grain and biomass yield. Also management of the land and the crop is important to ensure maximum benefits from inoculation  Soyabean has great potential to improve food, nutritional and income security of smallholder. Demand for soyabean in these areas has grown over the years (Mpepereki, 2010, Giller et al., 2011) Picture 1:soyabean fields (a) soyabean crop on good soil and good management (b)soyabean crop on poor soil and poor management. Both field crops were inoculated using standard rate  Native rhizobia populations are low and absent in these smallholder areas, hence there is need to inoculate to achieve favorable biomass and grain yields (Abaidoo et al., 2007)  New soil environments with low fertility- low pH, low organic matter soils also be explored to meet the soyabean increased demand.  This study aims to evaluate indigenous and exotic rhizobial strains and to identify promising soyabean- rhizobium combinations for smallholder cropping environments by measuring total nitrogen fixed, biomass and grain yield a a b Table 1: mean scores of strains in the different agro- ecolocical zones TREATMENT MEAN SCORE SC SAGA MUREWA NRII MEAN SCORE TGX MUREWA NRII MEAN SCORE SC SAGA MHONDOR O NRIII MEAN SCORE TGX NRIII MEAN SCORE SC SAGA MUDZI NR IV MEAN SCORE TGX NR IV NEG-CNTRL MAR MAR MAR MAR MAR MAR POS-CNTRL