Research Paper: Microorganism, Bradyrhizobium Japonicum, Displays

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[. . .] However, to assess which variable is more important in nodule formation is not possible because each variable exerts a significant effect on the other and are inter-related.

When analyzing the differences between each type of soil, the soil collected from the forest, being of clay loam soil, resulted in the least number of nodules. One explanation to this could be that forest roots are drought resistant roots and are planted deeper in the soil to allow it to draw more water. The depth of root could be an important limiting factor.

No relationship was found to exist between nodule formation and dry weight. Even though it was hypothesized that nodule formation should increase biomass, other factors, such as time duration, may have intervened in this relationship.

Legumes comprises of one of the most important agricultural taxa worldwide, accounting for twenty seven percent of world's crop production. Identifying factors that lead to better growth can have several important benefits. Nodules help the growth of pathogenic microorganisms on the plants they grow on and the plants that surround it. This decreases the need to use pesticides and decreases losses that can be created from plant destruction. Nodules also have a symbiotic relationship with legume species and can increase its protein content which has important dietary implications. (Graham & Caroll, 2003)

In most countries, legumes, such as soybeans, are grown towards the end of the growing season, which is after when corn and rice have been seeded. This gives the plants a short time to grow. They may also be subjected to the effects of drought, which alters the chemical and physical composition of soil. As determined by the results of this study, the type of soil and its density is crucial for the growth of soybeans, which grows best in loamy sand. Using this type of soil for agriculture can greatly increase crop productivity. (Graham & Caroll, 2003)

Legumes that are more drought resistant have deeper roots, reduced surface area of leaves and thicker cuticles. These mechanisms help reduce water loss. Drought resistant legumes can be grown later than the less tolerant legumes, such as beans, in order to maximize yield. (Graham & Caroll, 2003)

A study conducted by Sinclair, Zimet and Muchow (2003) determined the effects of irrigation on nodule formation and dry weights on field grown soybeans. This two-year study concluded that mild drought had no major effects on the dry weight and nodule formation of this type of legume. These results are in concordance to the results received by this study which determined that forest soil was the densest out of the three samples collected. However, the water content of each soil type need to be calculated before making generalizations about the degree of drought that can be tolerated by soybean plants.

The effect of the nutrient condition of the soil, pH and temperature might have been a limiting factor when determining the effects of different treatment. Phosphorus is one such nutrient that is found to be deficient in most soil types. A study was conducted to analyze this effect on nodule formation in soybean plants. The study concluded that adding phosphorus to the soil increased its content in the shoot and leaves. It also caused increased nitrogen content in the plants. The nodules did not increase in size at an inoculation of 102 cells mL-1 but at higher concentrations, there was a direct effect on the number and size of nodules. (Miao et al., 2007)

For better results, samples should have ideally been taken from different locations for each soil type. For instance, choosing more than one location for soil collection from the forest would have reduced the effect of chance.

When analyzing the results, the null hypothesis was rejected, at alpha = 0.05, since the effects of BradyrhizobiumJaponicum did not have a direct relationship to the dry weight. Rather, it was the effect of inoculation and different soil type that proved to be more important factors in determining dry weight and nodule formation.

Analysis of this research and others conclude that the most important factor that affects plant biomass is inoculation. Other factors such as temperature and pH may also play a role. The use of different types of soil was to assess a difference in nodule formation and dry weight in different soil densities. The type of soil used proved to be a significant factor in this study.


Evans, J., C, W., & N, D. (2002).Interaction of soil type and temperature on the survival of rhizobium leguminosarum.Soil biology and biochemistry, 25, 1153-1160.

Graham, P., & Caroll, P.V. (2003). Legumes: Importance and constraints to greater use. Plant Physiology, 131, 872-877.

Jenny, H. (2005). Factors of soil formation . (2 ed., pp. 197-261). NewYork: Dover.

Lindermann, W.C., & C.R, Glover.(2003). Nitrogen fixation by legumes. College of Agriculture and Home Economics, A-12, 1-4. Retrieved… [END OF PREVIEW]

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APA Format

Microorganism, Bradyrhizobium Japonicum, Displays.  (2012, March 7).  Retrieved May 26, 2019, from

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"Microorganism, Bradyrhizobium Japonicum, Displays."  7 March 2012.  Web.  26 May 2019. <>.

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"Microorganism, Bradyrhizobium Japonicum, Displays."  March 7, 2012.  Accessed May 26, 2019.