Evaluation of the soil carbon budget under different upland cropping systems in central Hokkaido,Japan

Abstract

To evaluate the carbon budget in soils under different cropping systems, the carbon dioxide (CO₂) flux from soils was measured in a total of 11 upland crop fields within a small watershed in central Hokkaido over the no snow cover months for 3 years. The CO₂ flux was measured using a closed chamber method at bare plots established in each field to estimate soil organic matter decomposition. Temporal variation in instantaneous soil CO₂ fluxes within the sites was mainly controlled by soil temperature and moisture. Annual mean CO₂ fluxes and cumulative CO₂ emissions had no significant relationship with soil temperature and moisture (P > 0.2). However, there was a significant quadratic relationship between annual mean CO₂ flux or cumulative CO₂ emission and soil clay plus silt content (%) (R² = 0.72～0.74, P < 0.0003). According to this relationship, the optimum condition for soil CO₂ emission is at a clay plus silt content of 63%. The cumulative CO₂ emission during the no snow cover season within each year varied from 1,159 to 7,349 kg C ha^?1 at the different sites. The amount of crop residue carbon retained in the soils following a cropping season was not enough to offset the CO₂ emission from soil organic matter decomposition at all sites. As a consequence, the calculation of the soil carbon budget (i.e. the difference between the carbon added as crop residues and compost and the carbon lost as CO₂ from organic matter decomposition) ranged from –7,349 to –785 kg C ha^?1, except for a wheat site where a positive value of 4,901 kg C ha^?1 was observed because of a large input of organic carbon with compost. The negative values of the soil carbon budget indicate that these cropping systems were net sources of atmospheric CO₂.     

Effects of bamboo biochar application on global warming in paddy fields in Ehime prefecture,Southern Japan

Biochar application can reduce global warming via carbon (C) sequestration in soils. However, there are few studies investigating its effects on greenhouse gases in rice (Oryza sativa L.) paddy fields throughout the year. In this study, a year-round field experiment was performed in rice paddy fields to investigate the effects of biochar application on methane (CH₄) and nitrous oxide (N₂O) emissions and C budget. The study was conducted on three rice paddy fields in Ehime prefecture, Japan, for 2 years. Control (Co) and biochar (B) treatments, in which 2-cm size bamboo biochar (2 Mg ha^?1) was applied, were set up in the first year. CH₄ and N₂O emissions and heterotrophic respiration (Rh) were measured using a closed-chamber method. In the fallow season, the mean N₂O emission during the experimental period was significantly lower in B (67 g N ha^?1) than Co (147 g N ha^?1). However, the mean CH₄ emission was slightly higher in B (2.3 kg C ha^?1) than Co (1.2 kg C ha^?1) in fallow season. The water-filled pore space increased more during the fallow season in B than Co. In B, soil was reduced more than in Co due to increasing soil moisture, which decreased N₂O and increased CH₄ emissions in the fallow season. In the rice-growing season, the mean N₂O emission tended to be lower in B (?104 g N ha^?1) than Co (?13 g N ha^?1), while mean CH₄ emission was similar between B (183 kg C ha^?1) and Co (173 kg C ha^?1). Due to the C release from applied biochar and soil organic C in the first year, Rh in B was higher than that in Co. The net greenhouse gas emission for 2 years considering biochar C, plant residue C, CH₄ and N₂O emissions, and Rh was lower in B (5.53 Mg CO₂eq ha^?1) than Co (11.1 Mg CO₂eq ha^?1). Biochar application worked for C accumulation, increasing plant residue C input, and mitigating N₂O emission by improving soil environmental conditions. This suggests that bamboo biochar application in paddy fields could aid in mitigating global warming.     

Suppressing methane emission and global warming potential from rice fields through intermittent drainage and green biomass amendment

Winter cover crops are recommended to improve soil quality and carbon sequestration, although their use as green manure can significantly increase methane (CH₄) emission from paddy soils. Soil management practices can be used to reduce CH₄ emission from paddy soils, but intermittent drainage is regarded as a key practice to reduce CH₄ emission and global warming potential (GWP). However, significantly greater emissions of carbon dioxide (CO₂) and nitrous oxide (N₂O) are expected when large amounts of cover crop biomass are incorporated into soils. In this study, we investigated the effects of midseason drainage on CH₄ emission and GWP following incorporation of 0, 3, 6 and 12 Mg/ha of cover crop biomass. Methane, CO₂ and N₂O emission rates significantly (P < 0.05) increased with higher rates of cover crop biomass incorporation under both irrigation conditions. However, intermittent drainage effectively reduced seasonal CH₄ fluxes by ca. 42–46% and GWP by 17–31% compared to continuous flooding. Moreover, there were no significant differences in rice yield between the two water management practices with similar biomass incorporation rates. In conclusion, intermittent drainage and incorporation of 3 Mg/ha of green biomass could be a good management option to reduce GWP.     

Controlled irrigation and drainage of a rice paddy field reduced global warming potential of its gas emissions

The effect of controlled drainage on methane (CH₄) and nitrous oxide (N₂O) emissions from a paddy field under controlled irrigation (CI) was investigated by controlling the sub-surface drainage percolation rate with a lysimeter. CI technology is one of the major water-saving irrigation methods for rice growing in China. Water percolation rates were adjusted to three values (2, 5, and 8 mm d^?1) in the study. On the one hand, the CH₄ emission flux and total CH₄ emission from paddy fields under CI decreased with the increase of percolation rates. Total CH₄ emissions during the growth stage of rice were 1.83, 1.16, and 1.05 g m^?2 in the 2, 5, and 8 mm d^?1 plots, respectively. On the other hand, the N₂O emission flux and total N₂O emissions from paddy fields under CI increased with the increase of percolation rates. Total N₂O emissions during the growth stage of rice were 0.304, 0.367, and 0.480 g m^?2 in the 2, 5, and 8 mm d^?1 plots, respectively. The seasonal carbon dioxide (CO₂) equivalent of CH₄ and N₂O emissions from paddy fields under CI was lowest in the 2 mm d^?1 plot (1364 kg CO₂ ha^?1). This value was 1.4% and 19.4% lower compared with that in the 5 and 8 mm d^?1 plots, respectively. The joint application of CI and controlled drainage may be an effective mitigation strategy for reducing the carbon dioxide equivalents of CH₄ and N₂O emissions from paddy fields.     

Nitrous oxide emissions from potato cropping under drip-fertigation in eastern Germany

In this article, a drip-fertigation system was compared to a control without irrigation concerning the amount of nitrous oxide (N₂O) emissions under the climatic conditions of north-east Germany. The investigation was carried out at a field research station in the federal state of Brandenburg. The mean N₂O emissions under drip-fertigation were significantly higher than under non-irrigation. The higher N₂O emissions under drip-fertigation can be explained by a constantly higher water-filled pore space (WFPS). These higher values in WFPS were caused by the necessary nutrient supply in combination with additional water application in periods with frequent rainfall.     

No significant difference in N2O emission,fertilizer-induced N2O emission factor and CH4 absorption between anaerobically digested cattle slurry and chemical fertilizer applied timothy (Phleum pratense L.) sward in central Hokkaido,Japan

Abstract

Nitrous oxide (N₂O) and methane (CH₄) fluxes from a fertilized timothy (Phleum pratense L.) sward on the northern island of Japan were measured over 2?years using a randomized block design in the field. The objectives of the present study were to obtain annual N₂O and CH₄ emission rates and to elucidate the effect of the applied material (control [no nitrogen], anaerobically digested cattle slurry [ADCS] or chemical fertilizer [CF]) and the application season (autumn or spring) on the annual N₂O emission, fertilizer-induced N₂O emission factor (EF) and the annual CH₄ absorption. Ammonium sulfate was applied to the CF plots at the same application rate of NH₄-N to the ADCS plots. A three-way ANOVA was used to examine the significance of the factors (the applied material, the application season and the year). The ANOVA for the annual N₂O emission rates showed a significant effect with regard to the applied material (P?=?0.042). The annual N₂O emission rate from the control plots (0.398?kg N₂O-N ha^?1?year^?1) was significantly lower than that from the ADCS plots (0.708?kg N₂O-N ha^?1?year^?1) and the CF plots (0.636?kg N₂O-N ha^?1?year^?1). There was no significant difference in the annual N₂O emission rate between the ADCS and CF plots. The ANOVA for the EFs showed insignificance of all factors (P?>?0.05). The total mean?±?standard error of the EFs (fertilizer-induced N₂O-N emission/total applied N) was 0.0024?±?0.0007 (kg N₂O-N [kg N]^?1), which is similar to the reported EF (0.0032?±?0.0013) for well-drained uplands in Japan. The CH₄ absorption rates differed significantly between years (P?=?0.014). The CH₄ absorption rate in the first year (3.28?kg CH₄?ha^?1?year^?1) was higher than that in the second year (2.31?kg CH₄?ha^?1?year^?1), probably as a result of lower precipitation in the first year. In conclusion, under the same application rate of NH₄-N, differences in the applied materials (ADCS or CF) and the application season (autumn or spring) led to no significant differences in N₂O emission, fertilizer-induced N₂O EF and CH₄ absorption.     

基于冬种不同作物的水旱轮作模式对水稻产量及稻田CH_4、N_2O排放的影响

为探究冬种不同作物、水旱轮作措施对稻田丰产及温室气体减排的影响,本研究设置5种种植模式,即紫云英-早稻-晚稻(CRR)、紫云英-早稻-甘薯‖晚大豆(CRI)、油菜-早稻-晚稻(RRR)、油菜-早稻-甘薯‖晚大豆(RRI)、马铃薯-早稻-晚稻(PRR),采用静态暗箱-气相色谱法测定稻田CH_4、N_2O的全年排放通量,研究基于冬季不同作物的不同水旱轮作模式对水稻产量、全球增温潜势(GWP)及温室气体排放强度(GHGI)的影响。结果表明,冬种不同作物均能提高早稻的产量,但对晚稻产量基本无影响,其中紫云英对早稻产量增效最好,CRI处理分别较其他处理高1.73%、12.08%、7.48%、10.95%;水旱轮作处理较双季稻处理可以获得更高的产量,RRI处理晚稻产量较其他4个处理分别高22.54%、5.37%、29.83%、27.24%。冬种不同作物对CH_4、N_2O排放无显著影响(P>0.05),水旱轮作显著增加了N_2O排放,显著降低了CH_4排放(P<0.05)。5种种植模式中,RRI处理的GWP最低,且显著低于CRR、RRR、PRR处理(P<0.05),分别低25.54%、29.76%、20.78%。RRI处理的GHGI最低,较其他处理分别显著低32.51%、18.18%、30.77%、20.59%(P<0.05)。综上,RRI处理在增加作物产量、减少稻田温室气体排放方面表现最好。本研究结果为长江中游双季稻区稻田丰产及温室气体减排提供了理论依据。     

Nitrous oxide and nitric oxide fluxes from cornfield,grassland, pasture and forest in a watershed in Southern Hokkaido,Japan

Abstract

To develop an advanced method for estimating nitrous oxide (N₂O) emission from an agricultural watershed, we used a closed-chamber technique to measure seasonal N₂O and nitric oxide (NO) fluxes in cornfields, grassland, pastures and forests at the Shizunai Experimental Livestock Farm (467 ha) in southern Hokkaido, Japan. From 2000 to 2004, N₂O and NO fluxes ranged from –137 to 8,920 µg N m^?2 h^?1 and from –12.1 to 185 µg N m^?2 h^?1, respectively. Most N₂O/NO ratios calculated on the basis of these N₂O and NO fluxes ranged between 1 and 100, and the log-normal N₂O/NO ratio was positively correlated with the log-normal N₂O fluxes (r ² = 0.346, P < 0.01). These high N₂O fluxes, therefore, resulted from increased denitrification activity. Annual N₂O emission rates ranged from –1.0 to 81 kg N ha^?1 year^?1 (average = 6.6 kg N ha^?1). As these emission values varied greatly and included extremely high values, we divided them into two groups: normal values (i.e. values lower than the overall average) and high values (i.e. values higher than average). The normal data were significantly positively correlated with N input (r ² = 0.61, P < 0.01) and the “higher” data from ungrazed fields were significantly positively correlated with N surplus (r ² = 0.96, P < 0.05). The calculated probability that a high N₂O flux would occur was weakly and positively correlated with precipitation from May to August. This probability can be used to represent annual variation in N₂O emission rates and to reduce the uncertainty in N₂O estimation.     

Life cycle inventory-based analysis of greenhouse gas emissions from arable land farming systems in Hokkaido,northern Japan

Abstract

To assess their impacts on net global warming, total greenhouse gas emissions (mainly CO₂, N₂O and CH₄) from agricultural production in arable land cropping systems in the Tokachi region of Hokkaido, Japan, were estimated using life cycle inventory (LCI) analysis. The LCI data included CO₂ emissions from on-farm and off-farm fossil fuel consumption, soil CO₂ emissions induced by the decomposition of soil organic matter, direct and indirect N₂O emissions from arable lands and CH₄ uptake by soils, which were then aggregated in CO₂-equivalents. Under plow-based conventional tillage (CT) cropping systems for winter wheat, sugar beet, adzuki bean, potato and cabbage, on-farm CO₂ emissions from fuel-consuming operations such as tractor-based field operations, truck transportation and mechanical grain drying ranged from 0.424 Mg CO₂ ha^?1 year^?1 for adzuki bean to 0.826 Mg CO₂ ha^?1 year^?1 for winter wheat. Off-farm CO₂ emissions resulting from the use of agricultural materials such as chemical fertilizers, biocides (pesticides and herbicides) and agricultural machines were estimated by input–output tables to range from 0.800 Mg CO₂ ha^?1 year^?1 for winter wheat to 1.724 Mg CO₂ ha^?1 year^?1 for sugar beet. Direct N₂O emissions previously measured in an Andosol field of this region showed a positive correlation with N fertilizer application rates. These emissions, expressed in CO₂-equivalents, ranged from 0.041 Mg CO₂ ha^?1 year^?1 for potato to 0.382 Mg CO₂ ha^?1 year^?1 for cabbage. Indirect N₂O emissions resulting from N leaching and surface runoff were estimated to range from 0.069 Mg CO₂ ha^?1 year^?1 for adzuki bean to 0.381 Mg CO₂ ha^?1 year^?1 for cabbage. The rates of CH₄ removal from the atmosphere by soil uptake were equivalent to only 0.020–0.042 Mg CO₂ ha^?1 year^?1. From the difference in the total soil C pools (0–20 cm depth) between 1981 and 2001, annual CO₂ emissions from the CT and reduced tillage (RT) soils were estimated to be 4.91 and 3.81 Mg CO₂ ha^?1 year^?1, respectively. In total, CO₂-equivalent greenhouse gas emissions under CT cropping systems in the Tokachi region of Hokkaido amounted to 6.97, 7.62, 6.44, 6.64 and 7.49 Mg CO₂ ha^?1 year^?1 for winter wheat, sugar beet, adzuki bean, potato and cabbage production, respectively. Overall, soil-derived CO₂ emissions accounted for a large proportion (64–76%) of the total greenhouse gas emissions. This illustrates that soil management practices that enhance C sequestration in soil may be an effective means to mitigate large greenhouse gas emissions from arable land cropping systems such as those in the Tokachi region of northern Japan. Under RT cropping systems, plowing after harvesting was omitted, and total greenhouse gas emissions from winter wheat, sugar beet and adzuki bean could be reduced by 18%, 4% and 18%, respectively, mainly as a result of a lower soil organic matter decomposition rate in the RT soil and a saving on the fuels used for plowing.     

Effect of the long-term application of organic matter on soil carbon accumulation and GHG emissions from a rice paddy field in a cool-temperate region,Japan-II. Effect of different compost applications-

ABSTRACT

The influence of long-term application of different types of compost on rice grain yield, CH₄ and N₂O emissions, and soil carbon storage (0 ? 30 cm) in rice paddy fields was clarified. Two sets of paddy fields applied with rice straw compost or livestock manure compost mainly derived from cattle were used in this study. Each set comprised long-term application (LT) and corresponding control (CT) plots. The application rates for rice straw compost (42 years) and livestock manure compost (41 years in total with different application rates) were 20 Mg fresh weight ha^–1. Soil carbon storage increased by 33% and 37% with long-term application of rice straw compost and livestock manure compost, respectively. The soil carbon sequestration rate by the organic matter application was 23% higher with the livestock manure compost than with the rice straw compost. The rice grain yield in the LT plot was significantly higher than that in the corresponding CT plot with both types of compost. Although the difference was not significant in the rice straw compost, cumulative CH₄ emissions increased with long-term application of both composts. Increase rate of CH₄ emission with long-term application was higher in the livestock manure compost (99%) than that in the rice straw compost (26%). In both composts, the long-term application did not increase N₂O emission significantly. As with the rice straw compost, the increase in CH₄ emission with the long-term application of livestock manure compost exceeded the soil carbon sequestration rate, and the change in the net greenhouse gas (GHG) balance calculated by the difference between them was positive, indicating a net increase in the GHG emissions. The increase in CH₄ and net GHG emissions owing to the long-term application of the livestock manure compost could be higher than that of the rice straw compost owing to the amount of applied carbon, the quality of compost and the soil carbon accumulation. The possibility that carbon sequestration in the subsoil differs depending on the type of composts suggests the importance of including subsoil in the evaluation of soil carbon sequestration by long-term application of organic matter.     

Evaluation of greenhouse gas emissions in a Miscanthus sinensis Andersson-dominated semi-natural grassland in Kumamoto,Japan

Increasing greenhouse gas emissions from anthropogenic activities continue to be a mounting problem worldwide. In the semi-natural Miscanthus sinensis Andersson; grasslands of Aso, Kumamoto, Japan, which have been managed for thousands of years, we measured soil methane (CH₄) and nitrous oxide (N₂O) emissions before and after annual controlled burns. We estimated annual soil carbon (C) accumulation, and CH₄ and N₂O emissions induced by biomass burning in 2009 and 2010, to determine the impacts of this ecosystem and its management on global warming. Environmental factors affecting soil CH₄ and N₂O fluxes were unknown, with no effect of annual burning observed on short-term soil CH₄ and N₂O emissions. However, deposition of charcoal during burning may have enhanced CH₄ oxidation and N₂O consumption at the study site, given that emissions (CH₄: ?4.33 kg C ha^?1 yr^?1, N₂O: 0.17 kg N ha^?1 yr^?1) were relatively lower than those measured in other land-use types. Despite significant emission of CH₄ and N₂O during yearly burning events in early spring, the M. sinensis semi-natural grassland had a large annual soil C accumulation, which resulted in a global warming potential of ?4.86 Mg CO₂eq ha^?1 yr^?1. Consequently, our results indicate that long-term maintenance of semi-natural M. sinensis grasslands by annual burning can contribute to the mitigation of global warming.     

不同耕作措施下小麦–玉米轮作农田温室气体 交换及其综合增温潜势

研究不同耕作措施下小麦-玉米轮作农田N_2O、CO_2和CH4等温室气体的综合增温潜势,有助于科学评价农业管理措施在减少温室气体排放和减缓全球变暖方面的作用,为制定温室气体减排措施提供依据。基于2001年开始的位于华北太行山前平原中国科学院栾城农业生态系统试验站的不同耕作与秸秆还田方式定位试验,应用静态箱/气相色谱法于2008年10月冬小麦播种时开始,连续两个作物轮作年动态监测了秸秆整秸覆盖免耕播种(M1)、秸秆粉碎覆盖免耕(M2)、秸秆粉碎还田旋耕(X)、秸秆粉碎还田深翻耕(F)和无秸秆还田深翻耕(CK,代表传统耕作方式)5种情况下冬小麦-夏玉米轮作农田土壤N_2O、CO_2和CH4排放通量,并估算其排放总量。试验期间同步记录每项农事活动机械燃油量、灌溉耗电量、施肥量,依据燃油、耗电和单位肥料量的碳排放系数统一转换为等碳当量,测定作物产量、地上部生物量,估算农田碳截存量,根据每个分支项对温室效应的作用估算了5个处理的综合增温潜势。结果表明,华北小麦-玉米轮作农田土壤是N2O和CO2的排放源,是CH4的吸收汇,每年M1、M2、X、F和CK农田土壤N2O排放总量依次为2.06 kg(N_2O-N)·hm~(-2)、2.28 kg(N_2O-N)·hm~(-2)、2.54 kg(N_2O-N)·hm~(-2)、3.87 kg(N2O-N)·hm~(-2)和2.29 kg(N2O-N)·hm~(-2),CO_2排放总量依次为6904 kg(CO_2-C)·hm~(-2)、7 351 kg(CO2-C)·hm~(-2)、8 873 kg(CO_2-C)·hm~(-2)、9 065 kg(CO2-C)·hm~(-2)和7 425 kg(CO2-C)·hm~(-2),CH4吸收量依次为2.50 kg(CH4-C)·hm~(-2)、1.77 kg(CH4-C)·hm~(-2)、1.33 kg(CH4-C)·hm~(-2)、1.38 kg(CH4-C)·hm~(-2)和1.57kg(CH4-C)·hm~(-2)。M1和M2处理农田生态系统综合增温潜势(GWP)均为负值,表明免耕情况下农田生态系统为大气的碳汇,去除农事活动引起的直接或间接排放的等当量碳,每年农田生态系统净截留碳947~1 070 kg(C)·hm~(-2);其他处理农田生态系统的GWP值均为正值,表明温室气体是由系统向大气排放,CK、F和X每年向大气分别排放等当量碳3 364 kg(C)·hm~(-2)、989 kg(C)·hm~(-2)和343 kg(C)·hm~(-2)。故华北小麦-玉米轮作体系中,秸秆粉碎还田旋耕是最优化的耕作措施,其温室效应相对较低,而又能保证较高的经济产量。     

Nitrous oxide emissions and nitrogen cycling in managed grassland in Southern Hokkaido,Japan

Abstract

Nitrous oxide (N₂O) emissions were measured and nitrogen (N) budgets were estimated for 2?years in the fertilizer, manure, control and bare plots established in a reed canary grass (Phalaris arundinacea L.) grassland in Southern Hokkaido, Japan. In the manure plot, beef cattle manure with bark was applied at a rate of 43–44?Mg fresh matter (236–310?kg?N)?ha^?1?year^?1, and a supplement of chemical fertilizer was also added to equalize the application rate of mineral N to that in the fertilizer plots (164–184?kg?N?ha^?1?year^?1). Grass was harvested twice per year. The total mineral N supply was estimated as the sum of the N deposition, chemical fertilizer application and gross mineralization of manure (GMm), soil (GMs), and root-litter (GMl). GMm, GMs and GMl were estimated by dividing the carbon dioxide production derived from the decomposition of soil organic matter, root-litter and manure by each C?:?N ratio (11.1 for soil, 15.5 for root-litter and 23.5 for manure). The N uptake in aboveground biomass for each growing season was equivalent to or greater than the external mineral N supply, which is composed of N deposition, chemical fertilizer application and GMm. However, there was a positive correlation between the N uptake in aboveground biomass and the total mineral N supply. It was assumed that 58% of the total mineral N supply was taken up by the grass. The N supply rates from soil and root-litter were estimated to be 331–384?kg?N?ha^?1?year^?1 and 94–165?kg?N?ha^?1?year^?1, respectively. These results indicated that the GMs and GMl also were significant inputs in the grassland N budget. The cumulative N₂O flux for each season showed a significant positive correlation with mineral N surplus, which was calculated as the difference between the total mineral N supply and N uptake in aboveground biomass. The emission factor of N₂O to mineral N surplus was estimated to be 1.2%. Furthermore, multiple regression analysis suggested that the N₂O emission factor increased with an increase in precipitation. Consequently, soil and root-litter as well as chemical fertilizer and manure were found to be major sources of mineral N supply in the grassland, and an optimum balance between mineral N supply and N uptake is required for reducing N₂O emission.     

Effect of the long-term application of organic matter on soil carbon accumulation and GHG emissions from a rice paddy field in a cool-temperate region,Japan. -I. Comparison of rice straw and rice straw compost -

ABSTRACT

The influence of the long-term combination of rice straw removal and rice straw compost application on methane (CH₄) and nitrous oxide (N₂O) emissions and soil carbon accumulation in rice paddy fields was clarified. In each of the initial and continuous application fields (3 and 39?51 years, respectively), three plots with different applications of organic matter were established, namely, rice straw application (RS), rice straw compost application (SC) and no application (NA) plots, and soil carbon storage (0?15 cm), rice grain yield and CH₄ and N₂O fluxes were measured for three years. The soil carbon sequestration rate by the organic matter application was higher in the SC plot than in the RS plot for both the initial and continuous application fields, and it was lower in the continuous application field than in the initial application field. The rice grain yield in the SC plot was significantly higher than those in the other plots in both the initial and continuous application fields. Cumulative CH₄ emissions followed the order of the NA plot < the SC plot < the RS plot for both the initial and continuous application fields. The effect of the organic matter application on the N₂O emissions was not clear. In both the initial and continuous application fields, the increase in CH₄ emission by the rice straw application exceeded the soil carbon sequestration rate, and the change in the net greenhouse gas (GHG) balance calculated by the difference between them was a positive, indicating a net increase in the GHG emissions. However, the change in the GHG balance by the rice straw compost application showed negative (mitigating GHG emissions) for the initial application field, whereas it showed positive for the continuous application field. Although the mitigation effect on the GHG emissions by the combination of the rice straw removal and rice straw compost application was reduced by 21% after 39 years long-term application, it is suggested that the combination treatment is a sustainable management that can mitigate GHG emissions and improve crop productivity.