Immediate effects of nitrogen, phosphorus, and potassium amendments on the methanotrophic activity and abundance in a Chinese paddy soil under short-term incubation experiment

Abstract

Methane-oxidizing bacteria (methanotrophs) biologically consume and consequently affect the concentration of atmospheric methane (CH4), the second most prominent greenhouse gas, and therefore play critical roles in the mitigation of global warming effect. Long-term fertilization often affects the methanotrophic community and CH4 oxidation in various soils. Here, the immediate effects of nitrogen (N), phosphorus (P), and potassium (K) amendments on the CH4 oxidation activity and methanotrophic community structure were evaluated. Paddy soil samples were collected from the Taoyuan Experimental Station of the Chinese Academy of Sciences in central Hunan Province of China. A laboratory-based incubation experiment was conducted to investigate the immediate effects of N, P, and K amendments on the methanotrophs in soil. The CH4 oxidation rates and methanotrophic activities were determined by measuring the dynamic changes of CH4 concentration in the incubation system. The methanotrophic abundance and community changes in all of the seven treatments with and without nutrients addition were studied using real-time PCR and denaturing gradient gel electrophoresis, respectively. All of the N, P, and K treatments significantly decreased the CH4 oxidation activities. Compared with the control, the P and K amendments significantly increased the methanotrophic population size, but the N treatments have no effect on the methanotrophic abundance. A negative correlation was found between methanotrophic activity and methanotrophic abundance. We suggested that methanotrophic activity may not be inferred through the pmoA gene copies, especially in the short-term simulation experiments. Investigation of the methanotrophic population size and diversity is not enough to evaluate the soil CH4 sink accurately. We concluded that the additions of N, P, and K reduce the activity but enhance the abundance of methanotrophs in a Chinese paddy soil through a short-term incubation experiment. Additionally, we found that the CH4 oxidation activity could be completely inhibited by Cl- toxicity. Our results implied that caution should be exercised in the types and amounts of fertilizers, especially KCl in agricultural systems to control the instantaneous increase in CH4 emission from the field.