The application of rapidly composted manure decreases paddy CH4 emission by adversely influencing methanogenic archaeal community: a greenhouse study

Abstract

The application of organic manure can alleviate the deterioration of soil quality. However, it inevitably increases paddy CH4 emissions by introducing more CH4-producing precursors, which further restricts the amendment of organic manure in paddy fields. A 17-week greenhouse pot experiment was conducted to compare the effects of noncomposted manure (NCM), commonly composted manure (CCM), and rapidly composted manure (RCM) on rice yield and CH4 emission. To understand CH4 emissions of these three different manures, both the population size and the community structure of the methanogenic archaea in the soils were also investigated. The experiment was carried out in a greenhouse with three treatments: NCM, CCM, and RCM. The CH4 fluxes during rice cultivation were measured using the closed static chamber technique, and the CH4 concentration was determined by FID gas chromatography (Agilent 7890, USA). Soil DNA was extracted from 0.5 g of moist soil using a FastDNA® SPIN Kit for soil (MP Biomedicals, Santa Ana, CA) according to the manufacturer’s instructions. The population size of methanotrophs and methanogenic archaea was determined by real-time quantitative PCR (qPCR), and the community composition was analyzed using pyrosequencing technology. Rice yield and CH4 emission significantly differed between the groups (P < 0.05) as follows: CCM < NCM < RCM and CCM < RCM < NCM, respectively. These results are, in part, due to the adverse effects of RCM on the soil methanogenic archaeal community. RCM is abundant in nitrogen, which can promote crop growth. The number of methanotrophs with the RCM treatment was the lowest, with no significant difference relative to that with the CCM treatment but significantly lower than that with the NCM treatment. RCM amendment decreased the abundance of total soil methanogenic archaea, specifically decreasing the abundances of two acetoclastic methanogenic guilds (Methanosarcina and Methanosaeta), and differentially altered the paddy methanogenic archaeal community structure at the rice tillering stage. These negative responses by methanogens led to the lower CH4 emissions with RCM treatment compared to that with NCM treatment. RCM amendment can guarantee high grain yield and can significantly decrease CH4 emission compared to the effects of fresh manure amendment. This phenomenon could result from the unique characteristics of RCM and its adverse effects on paddy methanogenic archaeal communities. Overall, RCM can be a beneficial alternative organic fertilizer, which can resolve the problem of increased rice production that leads to increased CH4 emission caused by the application of organic manure in the paddy ecosystem.