Symbiotic Nitrogen Fixation in Soybean

Soybean morphophysiology and yield response to seeding systems and plant populations

“…These results are relevant for shade issues, leaf senescence in the lower third, and flower and pod fixation (Board and Kahlon, 2011); they are also positive for phytosanitary control (Kumudini et al, 2008) and weed management (Arce et al, 2009 …”

Limitations and strategies to enhance biological nitrogen fixation in sub-humid tropics of Western Ethiopia

“…It is a wellestablished fact that, when legumes are grown in soils high in available nitrogen, the nitrogen fixation rate is reduced (Solomon et al, 2012;Saha et al, 2017 ). Inhibitory effect of nitrate causes the reduction of capillary roots development as well as preventing particular infection"s strands, indicating a shift from symbiotic to inorganic N nutrition (Coskan and Dogan, 2011). Therefore, it is possible to apply small amounts of soil N fertilizer, which may increase yield without reducing the amount of nitrogen fixed (Figure 1).…”

“…Nevertheless, it is generally accepted that symbiotically fixed N 2 is inadequate for realizing maximum seed yield, and that an application of small amounts of "starter" fertilizer N is needed to establish seedlings and promote early dinitrogen fixation (Sogut et al, 2013). However, application of large quantities of inorganic N inhibits the growth of rhizobia, nodulation and dinitrogen fixation (Coskan and Dogan, 2011). Herridge et al (1984) and Goi et al (1993) stated that under soils low in mineral N, a moderate dose of starter-N has been demonstrated to stimulate seedling growth and subsequently N-fixation.…”

“…The rate of nitrogen fixation was affected by many different physiological and environmental factors in soil, such as temperature, water holding capacity, water stress, salinity, nitrogen level, pH and other nutrients. Many of these factors, including temperature, affect many aspects of nitrogen fixation and assimilation, as well as factors such as respiratory activity, gaseous diffusion and solubility of dissolved gases, which ultimately affect plant growth (Coskan and Dogan, 2011).…”

“…Rhizobia require a plant host; therefore, they cannot independently fix nitrogen. These bacteria are located around root hair and fix atmospheric nitrogen using particular enzyme called nitrogenase (Coskan and Dogan, 2011). When this mutualistic symbiosis is established, rhizobia can use plant resources for their own reproduction whereas fixed atmospheric nitrogen is used to meet nitrogen requirement of both itself and the host plants.…”