Abstract
Soil microbes perform important functions in nitrogen and carbon cycling in the biosphere. Microbial communities in the rhizosphere enhance plants' health and promote nutrient turnover and cycling in the soil. In this study, we evaluated the effects of soil fertilization with organic and inorganic fertilizers on the abundances and distribution of carbon and nitrogen cycling genes within the rhizosphere of maize plants. Our result showed that maize plants through rhizosphere effects selected and enriched the same functional genes glnA, gltB, gudB involved in nitrogen cycle as do high compost and low inorganic fertilizer treatments. This observation was significantly different from those of high doses of inorganic fertilizer and low compost manure treated soil. Only alpha amylase encoding genes were selectively enriched by low compost and high inorganic fertilized soil. The other treatments only selected xynB (in Cp8), lacZ (Cp4), bglA, pldB, trpA (N2), uidA (N1) and glgC, vanA (Cn0) carbon cycling genes in the rhizosphere of maize. Also Actinomycetales are selected by high compost, low inorganic fertilizer and control. The control was without any fertilization and the soil was planted with maize. Bacillales are also promoted by low compost and high inorganic fertilizer. This indicated that only microbes capable of tolerating the stress of high dose of inorganic fertilizer will thrive under such condition. Therefore, soil fertilization lowers nitrogen gas emission as seen with the high abundance of nitrogen assimilation genes or microbial anabolic genes, but increases carbon dioxide evolution in the agricultural soil by promoting the abundance of catabolic genes involve in carbon cycling.