Straw application in paddy soil enhances methane production also from other carbon sources

Abstract

Abstract. Flooded rice fields are an important source of the greenhouse gas methane. Methane is produced from rice straw (RS), soil organic matter (SOM), and rice root organic carbon (ROC). Addition of RS is widely used for ameliorating soil fertility. However, this practice provides additional substrate for CH 4 production and results in increased CH 4 emission. Here, we found that decomposing RS is not only a substrate of CH 4 production, but in addition stimulates CH 4 production from SOM and ROC. Apart from accelerating the creation of reduced conditions in the soil environment, RS decomposition resulted in enhancement of SOM-derived CH 4 production. In particular, hydrogenotrophic methanogenesis from SOM-derived CO 2 was stimulated, presumably by H 2 released from RS decomposition. On the other hand, the enhancement of ROC-derived CH 4 production after RS application was probably caused by the significant increase of the abundance of methanogenic Archaea in the RS treatment compared with the untreated control. Our results show that traditional management of rice residues exerts a positive feedback on CH 4 production from rice fields, thus exacerbating its effect on the global CH 4 budget.

Fate of rice shoot and root residues, rhizodeposits, and microbe-assimilated carbon in paddy soil – Part 1: Decomposition and priming effect

“…The effluxes of both CO 2 and CH 4 from soils treated with 13 C-labelled substrates exhibited a rapid increase at the beginning of the incubation, followed by a slow decrease (Fig. 1), which indicated that microbes prefer fresh C substrates over native SOC (Yuan et al, 2014), as has been reported by previous studies on the decomposition of fresh C substrates in both paddy and upland soils (Lu et al, 2003;Parshotam et al, 2000). In these systems, the initial rapid decomposition is due to the addition of easily degradable organic C in the added substrates, such as starch and other labile compounds.…”

“…The aboveground biomass and root systems of rice plants represent one of the most important inputs of available organic C to paddy SOC (Johnson et al, 2006), the quantity and quality of which has been reported previously (Chen et al, 2014;Kisselle et al, 2001;Zhang et al, 2015). However, although aboveground biomass contributes significantly to SOC sequestration (Lu et al, 2003), rice roots have been reported to contribute from 1.5-to 3-fold more C to SOC than shoots (Hooker et al, 2005).…”

“…The transition could also involve an alteration in species dominance, with rapidly proliferating bacteria using more available compounds during the early stages of decomposition and slower-growing fungi using the more recalcitrant components during later stages (Baumann et al, 2009;Brant et al, 2006). Both CO 2 and CH 4 efflux are important components of the C cycle in paddy soils and represent a major proportion of the C released by microbial decomposition (Yuan et al, 2014), and the results of the present study suggest that the mineralization of shoot-and root-derived 13 C was ∼ 3-4 times higher than that of rhizodeposit-and microbe-derived 13 C (i.e. root-C > shoot-C > rhizo-C > micro-C; Fig.…”

Impact of Management Practices on Methane Emissions from Paddy Grown on Mineral Soil over Peat in Central Hokkaido, Japan

“…CH 4 fluxes were calculated from the linear increase or decrease of gas concentration in the chamber over time, using the following equation [21]:…”

Inclusion of microbial inoculants with straw mulch enhances grain yields from rice fields in central China

“…However, the influence of crop residue retention in the field on GHG emissions remains highly disputable. Many researchers argue that straw application could stimulate CH 4 emissions (Xu, Cai, Li, & Tsuruta, 2000;Yuan, Pump, & Conrad, 2014;Zhang, Zhang, Ma, Xu, & Cai, 2011), but some other researchers hold the opposite views (Zhang et al, 2013). Similarly, previous studies have proposed that straw returning could have either positive (Wang et al, 2016;Wu et al, 2018) or negative (Wang, Dalal, Reeves, Butterbach-Bahl, & Kiese, 2011) effects on N 2 O emissions.…”