Rotation benefit and population changes of soil hydrogen oxidizing bacteria in legume crop fields

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Root nodules of legumes (e.g. soybeans, alfalfa, etc.) have intracellular bacteria that can fix nitrogen gas into a form of nitrogen that the plant can use to make protein and nuclei acids. Hydrogen gas is a byproduct of the nitrogen fixing enzyme, nitrogenase, claiming about 33% of the energy that flows to the enzyme (the other 67% is used to reduce nitrogen gas). Legume nodules produce a large quantity of hydrogen gas, and release this into soils. For example, in Canadian alfalfa crop alone, we have estimated that there may be as much as 2.4 thousand million liters of hydrogen gas released to Canadian agricultural soils every year. If other legume crops are considered, the national hydrogen gas production rate may be twice as high. This hydrogen gas production can use up to 6% of the net daily gain of photosynthetically derived energy of the entire plant. We do not understand why evolutionary processes, plant breeding of agricultural crops, or selection of optimal nitrogen fixing bacteria has not reduced this energy loss in all legumes. Legumes are ideal crops to use in rotation with other crops (especially cereal crops), resulting in a significant increase in the growth and yield of the subsequent crop. Researchers have not been able to determine the basis for this yield enhancement. Only about 25% of the increase in the growth of the non-legume crop can be attributed to improved nitrogen nutrition. The remaining 75% of the effect have eluded explanation. We are proposing that the hydrogen released by nodules stimulates and support growth of certain soil hydrogen oxidizing bacteria.  These bacteria in return promote plant growth.  This hydrogen fertilization of soils may account for the beneficial effects of legumes on non-legume growth. The purposes of this study are to 1) analyze the soil bacterial community structure changes adjacent to nodules, 2) identify and characterize the hydrogen oxidizing bacteria in soil, 3) understanding the relationship between the hydrogen oxidizing bacteria in soils and soil fertility. The long-term goal of my research is to understand the relationship between the plant roots and soil microorganisms, especially the ones promoting the non-legume crop plants, to provide the practical protocols or inoculants for agriculture.