Abstract
There has been an increased interest in and wide application of biochar and slow-release fertilizer (SRF) to agricultural soils in recent years because they can reduce greenhouse gas emissions, but increase rice productivity. However, the studies considering combined effects of biochar and SRF are rare. This study examined the combined effects of biochar and SRF on the biogeochemistry, rice productivity, methane emission, and microbial abundances in rice paddy. The study sites included six different treatment combinations: urea (NU), SRF (NS), straw+urea (SU), straw+SRF (SS), biochar+urea (BU), and biochar+SRF (BS). Both the biochar and SRF reduced the methane emission, and the BS paddy soil had the lowest methane emission, while it had the highest rice yield. The biochar inhibited methanogenesis by increasing the soil aeration and oxygen availability. The SRF decreased the plant biomass, thus they may decrease plant-mediated methane transport and carbon substrate from plant debris and root exudates. Increasing in the abundance of methane-oxidizing bacteria was assumed to have critical impact on the reduction in methane emission by biochar. In conclusion, combined application of biochar and SRF highly recommended in rice cultivation, because they can minimize the methane emission but maximize rice yield.
Introduction
Biochar has been applied in a variety of terrestrial ecosystems in order to sequester biomass carbon into the ecosystems. In addition, many studies have sought ways to reduce methane emissions from rice paddies by applying biochar, because rice cultivation is a major source of methane. The global emission of methane from the rice paddy soil represents 30 to 40Tg CH a year, which accounts for almost 10% of the total anthropogenic methane emissions (Kirschke et al., 2013), and it’s still increasing due to rising demand for rice (Nguyen and Ferrero, 2006). Previous studies have reported that rice paddy with biochar had 8.8 to 28.0% higher rice yield than rice paddy without biochar (Zhang et al., 2010, Zhang et al., 2012, Wang et al., 2012), while biochar application reduced methane emission (Rondon et al., 2005, Karhu et al., 2011, Feng et al., 2012, Wang et al., 2012, Ly et al., 2015). Feng et al. (2012) suggested that increasing in methanotrophic proteobacterial abundances was responsible for decreasing in methane emission in biochar amended paddy soil. Zhang et al. (2010) showed that application of urea can increase rice productivity in rice paddy with biochar, but other types of N fertilizer are not considered in that study.
At the same time, slow-release fertilizer (SRF) has been applied to increase N use efficiency (NUE) and reduce emission of GHGs, without compromise in crop productivity (Abao et al., 2000, Li et al., 2006, Miao et al., 2015, Zhang et al., 2016). Zhang et al. (2016) reported that SRF-treated paddy soil had the lowest methane emission but the highest rice yield when compared with other types of nitrogen fertilizers. Miao et al. (2015) found that SRF significantly improved NUE, so rice yield was also improved. Although agricultural usage and academic interest of SRF have rapidly increased, but the effects of SRF on GHGs emission and other biogeochemical characteristics have not been fully understood in rice paddy ecosystem (Zhang et al., 2016). In addition, the effects of biochar and SRF on GHGs emission and soil biogeochemistry have been elucidated separately, but combined effects of biochar and SRF on rice paddy ecosystem still remain unclear.
Berger et al. (2013) suggested that methane emission from rice paddies is strongly affected by the microbial community of paddy soils, and Conrad (2002) suggested that integrated investigations on methanogens, methanotrophs and environmental factors are required to understand methane dynamics in rice paddy. Rice paddy is water-logged soil ecosystem, so this ecosystem is basically anaerobic. However, atmospheric oxygen could be supplied by diffusion and gas transport through aerenchyma, so aerobic methane oxidation could occur. Even though there are many studies having investigated methanogen and methanotroph in conventional rice paddy (Conrad, 2002, Shrestha et al., 2010, Ma et al., 2012, Lee et al., 2014), the study considering methanogen and methanotroph in rice paddy with biochar and SRF is rare. In this study, therefore, we investigated the aspect of microbiology in addition to biogeochemistry.
Overall, the study aimed to determine the combined effects of biochar and SRF on the biogeochemistry, productivity, methane emission, and microbial abundances from rice paddies over a cultivation period. Two types of C treatments (straw and biochar) and N fertilizers (urea and SRF) were used in this experiment. We designated an experimental rice paddy and cultivated rice using six different fertilization practices. We identified the mechanisms involved in the reduction of methane emissions from biochar and SRF, and conducted a microbial analysis to determine the effects of biochar and SRF on the abundances of related microbes.
Experimental design
Eighteen experimental plots were set up in a rice paddy in Hwaseong-si, Gyeonggi-do, South Korea (37°13’22“N, 127°02’32“E). The initial soil chemistry of the rice paddy soil is described in Table 1. The soil texture of the rice paddy was silt loam (Soil Survey Staff, 2014). The experiment had randomized 10m×5m rectangular plots with three replications that had the following six different treatments; NU (NoC treatment and Urea), NS (NoC treatment and SRF), SU (Straw and Urea), SS (Straw and…
Methane emission
The differences in methane emissions between the treatments were not significant in June and September, but were significant in July and August (Fig. 1). The cumulative methane emissions over the entire cultivation period were highest in the SU paddy soil, and were lowest in the BS paddy soil (Table 4). The BU paddy soil exhibited significantly lower methane emission than SU paddy soil. BS paddy soil exhibited marginally significantly lower methane emission than SS (P<0.07). There were two…
Effects on methane emission, biogeochemistry, and rice yield
During the cultivation period, an accumulation of soil organic matter was observed in all the paddy soils, except in the SU paddy soil. In the SU paddy soil, the activity of microbial decomposition may have been stimulated by the excessive supply of carbon and nitrogen substrate (Kögel-Knabner et al., 2010). Due to the high microbial decomposition, the soil organic matter could not accumulate inside the SU paddy soil, but was released into the atmosphere. The priming effect, acceleration of…
Conclusions
This study illustrated the combined effects of biochar and SRF on methane emission, rice yield, plant biomass, and the abundance of methanogen and methanotroph during cultivation period. Methane emission was significantly reduced by the application of biochar or SRF, and the biochar+SRF-treated paddy soil exhibited the lowest methane emission rate but the highest rice yield. Based on the results, we suggested that the biochar may reduce the methane emission by promoting methane oxidation by…
Funding
This work was supported by the funds from the National Research Foundations of Korea [20110030040, 2015K2A2A2002194], the Ministry of Education of Korea [2016R1D1A1A02937049], and the Rural Development Administration of Korea [PJ009253022014]….
Acknowledgements
Students’ Association of the Graduate School of Yonsei University provided valuable ideas to this manuscript….
References (46)
N. Eisenhauer et al.
Above- and below-ground plant inputs both fuel soil food webs
Soil. Biol. Biochem. (2012)
Y. Feng et al.
Mechanisms of biochar decreasing methane emission from Chinese paddy soils
Soil. Biol. Biochem. (2012)
A.J. Holmes et al.
Evidence that participate methane monooxygenase and ammonia monooxygenase may be
evolutionarily related
FEMS. Microbiol. Lett. (1995)
A. Holzapfel-Pschorn et al.
Production, oxidation and emission of methane in rice paddies
FEMS. Microbiol. Lett. (1985)
I. Kögel-Knabner et al.
Biogeochemistry of paddy soils
Geoderma (2010)
K. Karhu et al.
Biochar addition to agricultural soil increased ch4 uptake and water holding capacity – results
from a short-term pilot field study
Agr. Ecosyst. Environ. (2011)
Y. Kuzyakov et al.
Black carbon decomposition and incorporation into soil microbial biomass estimated by C
labeling
Soil. Biol. Biochem. (2009)
Y. Kuzyakov et al.
Biochar stability in soil: decomposition during eight years and transformation as assessed by
compound-specific C analysis
Soil. Biol. Biochem. (2014)
X. Sun et al.
Effect of plants on methane emissions from a temperate marsh in different seasons
Atmos. Environ. (2012)
K.L. Thomas et al.
Role of wetland plants in the diurnal control of CH and CO fluxes in peat
Soil. Biol. Biochem. (1996)
Paddy rice yield and greenhouse gas emissions: Any trade-off due to co-application of biochar
and nitrogen fertilizer? A systematic review
2023, Heliyon
Carbon farming training and welfare: Evidence from Northern Ghana
2023, Land Use Policy
Effects of nitrogen co-application by different biochar materials on rice production potential
and greenhouse gas emissions in paddy fields in northern China
Degradation reduces greenhouse gas emissions while weakening ecosystem carbon
sequestration of Moso bamboo forests
2023, Science of the Total Environment
Liquid-solid ratio during hydrothermal carbonization affects hydrochar application potential in
soil: Based on characteristics comparison and economic benefit analysis
2023, Journal of Environmental Management
