Cultivar maturity and potential yield of soybean
Soybean (Glycine max (L.) Merrill) cultivars from maturity groups 00, I, III, and V were grown in the field to evaluate the relationship between the length of total growth cycle and potential yield. Cultivars from maturity group 00 and I were grown in narrow rows (0.38 m) to obtain maximum insolation interception. The length of the vegetative growth period increased by 35 days from maturity group 00 to V. Plant size (total nodes per plant and maximum vegetative mass in g m−2) also increased with increasing maturity group. All cultivars reached maximum insolation interception soon after initial flowering. The crop growth rate of control plots (measured between growth stages R1 and R5) was not related to plant size. Shade (30 and 63%) from growth stage R1 to R7 was used to create variation in crop growth rate within a cultivar. For each cultivar, the number of seeds m−2 increased linearly with increasing crop growth rate. After adjusting for cultivar differences in individual seed growth rate, there were no cultivar differences in seeds m−2 at a constant crop growth rate. Thus, seeds m−2 was related to crop growth rate, not to the size of the plant. The maturity growth 00 cultivar tended to have a shorter seed-filling period but there were no consistent differences among the others. These data suggest that the longer vegetative growth period of later-maturing cultivars does not provide a higher yield potential and that shorter-season cultivars may have equal yield potential if exposed to a similar environment. 
Associative effect ofAzospirilium brasilense withRhizobium japonicum on nodulation and yield of soybean (Glycine max)
Azospirillum was associated with nodules of soybean. In general, seed inoculation with a broth culture ofAzospirillum brasilense alone significantly increased nodulation and grain yield of soybean grown in pots in unsterilized soil with different levels of urea ranging from 0 to 80 kg N/ha. This trend was significantly reproducible in a second experiment when a carrier based inoculant of the bacterium was used for seed inoculation.
Inoculation withRhizobium japonicum andA. brasilense in combination generally increased grain yield in both the experiments, although the data were not significant. 
Putative Alleles for Increased Yield from Soybean Plant Introductions
Improving seed yield of soybean [Glycine max (L.) Merr.] is an important breeding goal. The objective of this study was to evaluate two soybean PIs as sources of alleles for the enhancement of seed yield in North American cultivars. A population of 167 F5–derived lines was developed from a cross between ‘BSR 101’ and the experimental line LG82‐8379. BSR 101 has nine of 10 major ancestral lines contributing to the commercial gene pool of North America, while LG82‐8379 was selected from a cross between PI 68508 and FC 04007B. The F5–derived lines, divided into three sets based on maturity, were evaluated for 145 polymorphic simple sequence repeat (SSR) marker loci and for seed yield and other agronomic traits in 12 environments. Fifteen quantitative trait loci (QTL) were significantly [P < 0.05, likelihood of odds (LOD) > 2.5] associated with seed yield in at least one set with two significant across all sets. For nine of the yield QTL, the LG82‐8379 alleles were associated with yield increases of 1.7 to 5.4% while the BSR 101 alleles increased yield 2.4 to 4.4% at six yield QTL. Four yield QTL were associated with significant changes in R8, eight with plant height, and three with seed protein concentration. Additional QTL were identified for R8, plant height, lodging, and seed protein and oil concentration. These results indicate that soybean PIs have the genetic potential for improving seed yield of U.S. soybean cultivars. 
Phosphorus Application and Rhizobia Inoculation on Growth and Yield of Soybean (Glycine max L. Merrill)
An experiment was conducted in the major and minor cropping seasons of 2012 and 2013 under field conditions at Bolgatanga Polytechnic, to study the effect of phosphorus fertilizer and Rhizobia inoculation on growth and yield of soybean using randomized complete block design and three replications. The treatments studied were: Soybean + phosphorus fertilizer + Rhizobia inoculation (+P/+I), Soybean + phosphorus fertilizer only (+P/-I), Soybean inoculated with Rhizobia (-P/+I) and the control-Soybean only (-P/-I). Results indicated that Phosphorus fertilizer application is required for shoot growth, pod and seed yield. Nodulation and root growth were significantly increased by Phosphorus + Rhizobia inoculation (+P/+I) but P fertilizer only did not enhance root growth. Dry matter accumulation was highest between onset of flowering and Podding. Grain yield was again highest for Rhizobia inoculation plus Phosphorus fertilizer (+P/+I) and Phosphorus fertilizer only (+P/-I) recording 7.61 t/ha and 7.30 t/ha respectively whiles Rhizobia inoculation only (-P/+I) and the control (-P/-I) produced the lowest grain yield (4.41 t/ha) and (3.80 t/ha) respectively. 
Soybean (Glycine max L) Genotype and Environment Interaction Effect on Yield and Other Related Traits
Aims: To evaluate genetic variability of five soybean genotypes, and assess genotype × environment effect on seed yield and yield related traits.
Study Design: Split-plot, replicated three times. Genotypes were fixed effect while plots (main 60 m² and subplot 12 m²) were random effects. The sub-plot consists of 4 rows 5 m long with 60 cm and 10 cm inter and intra-row spacing.
Place and Duration: El Gantra, Range and Pasture Farm in Sennar State of the Sudan during 2009 and 2010 cropping season.
Methodology: Five soybean genotypes NA 5009 RG; TGx 1904-6F, TGx 1740-2F, TGx 1937-1F and Soja were evaluated. A strain of Rhizobium japonicum was used for inoculation at a rate of 10 g per kg of soybean seed using a sugary solution in 2009. Inoculation was not carried out due to the assumption that the field had the remnant of inoculum effect in 2010. All the recommended soybean agronomic practices were equally applied. Number of days to 50% flowering was recorded on plot basis when almost half of the sub-plot flowers. Ten plants were randomly selected on plot basis to quantify these traits: Plant height was measured as from ground surface to the base of meri-stem of the mother plant. Number of branches was computed as an average count of branches per plant. Leaf area was computed using Iamauti  empirical relationship. The first pod height was measured at full bloom. Number of seeds per pod was counted at physiological maturity of the crop. 100-seed weight was determined randomly from a seed bulk using a digital weighing machine. Seed yield was quantified after harvest and converted into kg/hectare.
Results: The effect of genotype (G), environment (E) and G × E interactions on pod number per plant; plant height, first pod height, number of branches per plant, leaf area, number of days to 50% flowering and seed yield were found significant at P=0.05. The highest mean seed yield was obtained from TGx 1937-1F (0.98 t/ha). Beside TGx 1740-2F, TGx 1904-6F and Soja were significantly higher than NA 5009 RG in all environments for seed yield. TGx 1937-1F was an intermediate maturing and best in terms of number of pods per plant, number of branches per plant, and leaf area. Correlation coefficient for seed yield showed significant association with days to 50% flowering and leaf area.
Conclusion: The best genotype for seed yield across the environments was TGx 1937-1F and TGx 1740-2F, TGx1904-6F and Soja were intermediate and NA 5009 RG was the least. Thus, partitioning G × E into adaptability and phenotypic stability will positively address the information gap on association of traits to yield. 
 Egli, D.B., 1993. Cultivar maturity and potential yield of soybean. Field Crops Research, 32(1-2), pp.147-158.
 Singh, C.S. and Rao, N.S., 1979. Associative effect ofAzospirilium brasilense withRhizobium japonicum on nodulation and yield of soybean (Glycine max). Plant and Soil, 53(3), pp.387-392.
 Kabelka, E.A., Diers, B.W., Fehr, W.R., LeRoy, A.R., Baianu, I.C., You, T., Neece, D.J. and Nelson, R.L., 2004. Putative alleles for increased yield from soybean plant introductions. Crop science, 44(3), pp.784-791.
 M. Akpalu, M., Siewobr, H., Oppong-Sekyere, D. and E. Akpalu, S. (2014) “Phosphorus Application and Rhizobia Inoculation on Growth and Yield of Soybean (Glycine max L. Merrill)”, Journal of Experimental Agriculture International, 4(6), pp. 674-685. doi: 10.9734/AJEA/2014/7110.
 Ngalamu, T., Ashraf, M. and Meseka, S. (2013) “Soybean (Glycine max L) Genotype and Environment Interaction Effect on Yield and Other Related Traits”, Journal of Experimental Agriculture International, 3(4), pp. 977-987. doi: 10.9734/AJEA/2013/5069.