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1.
Biological methane oxidation is a crucial process in the global carbon cycle that reduces methane emissions from paddy fields and natural wetlands into the atmosphere.However,soil organic carbon accumulation associated with microbial methane oxidation is poorly understood.Therefore,to investigate methane-derived carbon incorporation into soil organic matter,paddy soils originated from different parent materials(Inceptisol,Entisol,and Alfisol) were collected after rice harvesting from four major rice-producing regions in Bangladesh.Following microcosm incubation with 5%(volume/volume)13 CH4,soil13 C-atom abundances significantly increased from background level of 1.08% to 1.88%–2.78%,leading to a net methane-derived accumulation of soil organic carbon ranging from 120 to 307 mg kg-1.Approximately 23.6%–60.0% of the methane consumed was converted to soil organic carbon during microbial methane oxidation.The phylogeny of13 C-labeled pmoA(enconding the alpha subunit of the particulate methane monooxygenase) and 16 S rRNA genes further revealed that canonical α(type II) and γ(type I) Proteobacteria were active methane oxidizers.Members within the Methylobacter-and Methylosarcina-affiliated type Ia lineages dominated active methane-oxidizing communities that were responsible for the majority of methane-derived carbon accumulation in all three paddy soils,while Methylocystis-affiliated type IIa lineage was the key contributor in one paddy soil of Inceptisol origin.These results suggest that methanotroph-mediated synthesis of biomass plays an important role in soil organic matter accumulation.This study thus supports the concept that methanotrophs not only consume the greenhouse gas methane but also serve as a key biotic factor in maintaining soil fertility.  相似文献   

2.
Impacts of biochar addition on nitrous oxide (N2O) and carbon dioxide (CO2) emissions from paddy soils are not well documented. Here, we have hypothesized that N2O emissions from paddy soils could be depressed by biochar incorporation during the upland crop season without any effect on CO2 emissions. Therefore, we have carried out the 60-day aerobic incubation experiment to investigate the influences of rice husk biochar incorporation (50 t ha−1) into two typical paddy soils with or without nitrogen (N) fertilizer on N2O and CO2 evolution from soil. Biochar addition significantly decreased N2O emissions during the 60-day period by 73.1% as an average value while the inhibition ranged from 51.4% to 93.5% (P < 0.05–0.01) in terms of cumulative emissions. Significant interactions were observed between biochar, N fertilizer, and soil type indicating that the effect of biochar addition on N2O emissions was influenced by soil type. Moreover, biochar addition did not increase CO2 emissions from both paddy soils (P > 0.05) in terms of cumulative emissions. Therefore, biochar can be added to paddy fields during the upland crop growing season to mitigate N2O evolution and thus global warming.  相似文献   

3.
The application of biochar produced from wood and crop residues, such as sawdust, straw, sugar bagasse and rice hulls, to highly weathered soils under tropical conditions has been shown to influence soil greenhouse gas (GHG) emissions. However, there is a lack of data concerning GHG emissions from soils amended with biochar derived from manure, and from soils outside tropical and subtropical regions. The objective of this study was to quantify the effect on emissions of carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) following the addition, at a rate of 18 t ha−1, of two different types of biochar to an Irish tillage soil. A soil column experiment was designed to compare three treatments (n = 8): (1) non-amended soil (2) soil mixed with biochar derived from the separated solid fraction of anaerobically digested pig manure and (3) soil mixed with biochar derived from Sitka Spruce (Picea sitchensis). The soil columns were incubated at 10 °C and 75% relative humidity, and leached with 80 mL distilled water, twice per week. Following 10 weeks of incubation, pig manure, equivalent to 170 kg nitrogen ha−1 and 36 kg phosphorus ha−1, was applied to half of the columns in each treatment (n = 4). Gaseous emissions were analysed for 28 days following manure application. Biochar addition to the soil increased N2O emissions in the pig manure-amended column, most likely as a result of increased denitrification caused by higher water filled pore space and organic carbon (C) contents. Biochar addition to soil also increased CO2 emissions. This was caused by increased rates of C mineralisation in these columns, either due to mineralisation of the labile C added with the biochar, or through increased mineralisation of the soil organic matter.  相似文献   

4.
水稻植株特性对稻田甲烷排放的影响及其机制的研究进展   总被引：6，自引：0，他引：6  
水稻是我国最主要的口粮作物,稻田是重要温室气体甲烷的主要排放源之一。水稻植株特性既是水稻产量形成的关键因子,也是稻田甲烷排放的主要影响因子。但是,至今关于水稻植株对稻田甲烷排放的调控效应及其机制仍存在许多不一致的认识。为此,本文从形态特征、生理生态特征、植株-环境互作等方面,对现有的相关研究进行了综合论述。水稻地上部形态特征如分蘖数、株高、叶面积等对稻田甲烷排放的影响的研究结果不尽相同,起关键作用的是地下系统。优化光合产物分配在持续淹水的情况下可以减少稻田甲烷排放。提高水稻生物量在低碳土壤增加稻田甲烷排放,但在高碳土壤下降低甲烷排放。本文还明确了相关研究现状和存在的问题。在此基础上,作者认为未来应加强水稻根系形态及其生理特征,以及水稻植株-土壤环境(尤其是水分管理和养分管理)互作对稻田甲烷产生、氧化和排放影响的研究,在方法上应加强微区试验和大田试验的结合,并开展植株和稻田的碳氮互作效应及其机制研究,为高产低碳排放的水稻品种选育和低碳稻作模式创新提供理论参考和技术指导。  相似文献   

5.
Solar vegetable greenhouse soils show low soil organic carbon content and thus also low rates of soil respiration. Processing vegetable residues to biochar and mixing biochar with maize straw might improve soil respiration and increase soil organic carbon stocks, while preventing the spread of soil-borne diseases carried by vegetable residues. In an incubation experiment, we tested how additions of maize straw (S) and biochar (B) added in varying ratios (100S, 75S25B, 50S50B, 25S75B, 100B and 0S0B (control)) affect soil respiration and fraction of added C remaining in soil. Daily CO2 emissions were measured over 60 days incubation, the natural abundance of 13C in soil and in the added biochar and maize straw were analysed. Our result shows that (a) soil CO2 emissions were significantly increased compared to soil without the straw additions, while addition of biochar only decreased soil respiration; (b) cumulative CO2 emissions decreased with increasing ratio of added biochar to maize straw; (c) the abundance of soil 13C was significant positively correlated with cumulative CO2 emissions, and thus with the ratio of straw addition. Our results indicate that incorporation of maize straw in greenhouse soils is a meaningful measure to increase soil respiration and to facilitate greenhouse atmosphere CO2 limitation while producing vegetables. On the other hand, additions of biochar from vegetable residues will increase soil organic carbon concentration. Therefore, the simultaneous application of maize straw and biochar obtained from vegetable residues is an effective option to maintain essential soil functions for vegetable production in sunken solar greenhouses.  相似文献   

6.
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.  相似文献   

7.
Abstract

The scenarios for conventional puddling and no-tilling rice (Oryza sativa L.) cultivation were compared in terms of greenhouse gas (GHG) emissions from paddy fields, fuel consumption and manufacturing of invested materials using a life cycle inventory (LCI) based analysis. Only the differences between the scenarios were examined. The no-tilling scenario omitted both tilling and puddling, but included spraying of a non-selective herbicide and used a transplanter equipped with a rotor. Fertilization was a basal single application of controlled release fertilizer in nursery boxes for all scenarios. After transplanting, there were no differences in machine work, invested materials or rice yields between the scenarios. The no-tilling scenario saved on fuel consumption, totaling carbon dioxide (CO2) output of 42 kg ha?1, which was equal to the 6% reported GHG emissions from fuel consumption by operating machines during rice production in Japan. Methane (CH4) and nitrous oxide (N2O) emissions from the paddy fields were also monitored and compared for the scenarios. Methane has a major effect on global warming as part of the GHG emitted from paddy fields. The cumulative CH4 emissions from the no-tilling cultivation were 43% lower than those from conventional puddling cultivation because the plow layer was more oxidative in no-tilling cultivation. The N2O emissions were not significantly different between the cultivation scenarios. There were no significant differences in soil respiration, soil carbon contents or straw yields between the cultivation scenarios. The effect of tillage on CO2 flux in the paddy fields did not seem to be significant in this study. Consequently, the GHG emissions from the no-tilling field counted as CO2 using global warming potentials were 1,741 kg CO2 ha?1 lower than those from the conventional puddling field. In conclusion, no-tilling rice cultivation has the potential to save 1,783 kg CO2 ha?1 calculated using the sum of fuel consumption and GHG emissions from paddy fields. No-tilling rice cultivation is considered to be environmentally friendly agriculture with respect to reducing GHG emissions.  相似文献   

8.
Abstract

Iron oxide is the most important electron acceptor in paddy fields. We aimed to suppress the methane emission from paddy fields over the long term by single application of iron materials. A revolving furnace slag (RFS; 245 g Fe kg-1) and a spent disposable portable body warmer (PBW; 550 g Fe kg-1) were used as iron materials. Samples of a soil with a low iron level (18.5 g Fe kg-1), hearafter referred to as “a low-iron soil” and of a soil with a high iron level (28.5 g Fe kg-1), hearafter referred to as “an iron-rich soil,” were put into 3 L pots. At the beginning of the experiment, RFS was applied to the pots at the rate of 20 and 40 t ha-1, while PBW was applied at the rate of 10 t ha-1 only, and in the control both were not applied. Methane and nitrous oxide emissions from the potted soils with rice plants were measured by the closed chamber method in 2001 and 2002. When RFS was applied at the rates of 20 and 40 t ha-1 to the low-iron soil, the total methane emission during the cultivation period significantly decreased by 25–50% without a loss of grain yield. Applied iron materials clearly acted as electron acceptors, based on the increase in the amount of ferrous iron in soil. However, the suppressive effect was not evident in the iron-rich soil treated with RFS or PBW. On the other hand, nitrous oxide emission increased by 30–95%. As a whole, when the total methane and nitrous oxide emissions in the low-iron soil were converted to total greenhouse gas emissions expressed as CO2- C equivalents in line with the global warming potential, the total greenhouse gas emissions decreased by about 50% due to the application of RFS.  相似文献   

9.
Paddy soils are subjected to periodically changing redox conditions. In order to understand better the redox control on long‐term carbon turnover, we assessed carbon mineralization and dissolved organic carbon (DOC) of paddy topsoils sampled along a chronosequence spanning 2000 years of rice cultivation. Non‐paddy soils were used as references. We exposed soils to alternating redox conditions for 12 weeks in incubation experiments. Carbon mineralization of paddy soils was independent of redox conditions. Anoxic conditions caused increasing DOC concentrations for paddy soils, probably because of desorption induced by increasing pH. We assume desorption released older, previously stabilized carbon, which then was respired by a microbial community well adapted to anoxic conditions. This assumption is supported by the 14C signatures of respired CO2, indicating larger mineralization of older carbon under anoxic than under oxic conditions. The increasing DOC concentrations under anoxic conditions did not result in an equivalent increase in carbon mineralization, possibly because of little reducible iron oxide. Therefore, net DOC and CO2 production were not positively related under anoxic conditions. The overall 20–75% smaller carbon mineralization of paddy soils than of non‐paddy soils resulted from less respiration under oxic conditions. We conclude that carbon accumulation in paddy as well as in other wetland soils results from a microbial community well adapted to anoxic conditions, but less efficient in mineralizing carbon during transient oxic periods. Carbon accumulation might be even larger when mineralization under anoxic conditions is restricted by a lack of alternative electron acceptors.  相似文献   

10.
Understanding the greenhouse gas(GHG)emission from rice paddy fields is essential to come up with appropriate countermeasure in response to global warming.However,GHG emissions from paddy fields in South Korea are not well characterized.The objectives of this study were to estimate the carbon dioxide(CO2)and methane(CH4)emissions from rice paddy fields in South Korea,under the Representative Concentration Pathway 8.5(RCP-8.5)climate change scenario using the DNDC(i.e.,DeNitrification-DeComposition)model at 1-km2resolution.The performance of the model was verified with field data collected using a closed chamber,which supports the application of the model to South Korea.Both the model predictions and field measurements showed that most(>95%)GHG emissions occur in the cropping period,between April and October.As a baseline(assuming no climate change),the national sums of the CO2and CH4emissions for the 2020 s and 2090 s were estimated to be 5.8×106and 6.0×106t CO2-equivalents(CO2-eq)year-1for CO2and 6.4×106and 6.6×106t CO2-eq year-1for CH4,respectively,indicating no significant changes over 80 years.Under RCP-8.5,in the 2090 s,CH4emissions were predicted to increase by 10.7×106and 14.9×106t CO2-eq year-1,for a 10-or 30-cm tillage depth,respectively.However,the CO2emissions gradually decreased with rising temperatures,due to reduced root respiration.Deep tillage increased the emissions of both GHGs,with a more pronounced effect for CH4than CO2.Intermittent drainage in the middle of the cropping season can attenuate the CH4emissions from paddy fields.The findings of this work will aid in developing nationwide policies on agricultural land management in the face of climate change.  相似文献   

11.
To accurately predict the potential environmental benefits of energy crops, the sequestration of carbon in soil needs to be quantified. The aim of this study was to investigate the mineralisation rate of the perennial C4 grass Miscanthus giganteus and Miscanthus-derived soil organic matter under contrasting nitrogen supply. Soils were collected from sites where Miscanthus had been grown for 11 and 18 years, respectively, and where a C3-grass (Lolium spp.) had been grown for 7 years. The soils were incubated for 4 months at two levels of soil inorganic nitrogen with or without dead root material of Miscanthus.Addition of root material (residues) increased carbon mineralisation of indigenous organic matter when no nitrogen was added. Added inorganic nitrogen decreased carbon mineralisation in all soils. Nitrogen addition did not affect carbon mineralisation of the residues. Using the 13C fraction to calculate the proportion of respiratory CO2 derived from Miscanthus showed that nitrogen addition decreased carbon mineralisation in soils, but it did not affect carbon mineralisation of the residues. Nitrogen mineralisation was highest in the C3 grass soil without added residues. Nitrification decreased pH, especially in the treatments where nitrogen was added. The Miscanthus-derived organic matter is at least as stable as C3 grassland-derived organic matter. Furthermore, the turnover time of the organic matter increases with time under Miscanthus cultivation.The CENTURY soil organic matter sub-model was used to simulate the organic matter decomposition in the experiment. Carbon mineralisation was accurately simulated but there were unexplained discrepancies in the simulation of the δ13C in the respiration from the treatment with residues. The δ13C in respiration did not decrease with time as predicted, indicating that lignin accumulation did not influence the measurements.  相似文献   

12.
Global warming is now attracting the world attention. Methane is an important greenhouse gas next to CO2. Prather et al. (1995) estimated that rice paddy fields account for 14% of all biogenic atmospheric methane. It is considered that methane production from rice paddy fields is increasing along with the increase of the population. Therefore, the development of rice cultivation techniques for reducing methane production is essential, in order to preserve the global environment.  相似文献   

13.
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.  相似文献   

14.
Abstract

A short-term study was conducted to investigate the greenhouse gas emissions in five typical soils under two crop residue management practices: raw rice straw (Oryza sativa L., cv) and its derived biochar application. Rice straw and its derived biochar (two biochars, produced at 350 and 500°C and referred to as BC350 and BC500, respectively) were incubated with the soils at a 5% (weight/weight) rate and under 70% water holding capacity for 28 d. Incorporation of BC500 into soils reduced carbon dioxide (CO2) and nitrous oxide (N2O) emission in all five soils by 4?40% and 62?98%, respectively, compared to the untreated soils, whereas methane (CH4) emission was elevated by up to about 2 times. Contrary to the biochars, direct return of the straw to soil reduced CH4 emission by 22?69%, whereas CO2 increased by 4 to 34 times. For N2O emission, return of rice straw to soil reduced it by over 80% in two soils, while it increased by up to 14 times in other three soils. When all three greenhouse gases were normalized on the CO2 basis, the global warming potential in all treatments followed the order of straw > BC350 > control > BC500 in all five soils. The results indicated that turning rice straw into biochar followed by its incorporation into soil was an effective measure for reducing soil greenhouse gas emission, and the effectiveness increased with increasing biochar production temperature, whereas direct return of straw to soil enhanced soil greenhouse gas emissions.  相似文献   

15.
A pot incubation experiment with rice residues (straw and root) was conducted under aerobic condition (60% of WHC, water holding capacity) for a period of 55 days in a greenhouse. The emissions of carbon dioxide (CO2) and nitrous oxide (N2O) were determined by the closed chamber method in a paddy soil. The soil was derived from quaternary red clay, and collected from the Ecological Station of Red Soil, the Chinese Academy of Sciences, located in Jiangxi Province, a subtropical region of China. The emissions of CO2 and N2O were increased by the amendment of rice residues. Significantly positive correlation was found between N2O and CO2 fluxes (R = 0.650*?0.870*, P ≤ 0.05). The cumulative emissions during the early stage of the incubation (<25 days after residue addition) accounted for about 67%–86% and 67%–80% of the total amount of CO2 and N2O emissions, respectively. Cumulative emissions and emission factors of the two gases were higher in the soils amended with rice straw than those with rice root. The two gas fluxes were positively correlated with microbial biomass C and N, as well as soluble organic C. N2O flux was positively correlated with NH4 +–N content at the early stage (<25 days), and negatively with NO3 ?–N content at the later stage of this incubation (25–55 days), implying that both nitrification and denitrification may have contributed to N2O production.  相似文献   

16.
王强盛  刘欣  许国春  余坤龙  张慧 《土壤》2023,55(6):1279-1288
稻田是大气温室气体甲烷(CH4)和氧化亚氮(N2O)的重要排放源, 稻田温室气体减排一直是生态农业研究的热点。目前, 采用水稻品种选择利用、水分控制管理、肥料运筹管理、耕作制度调整以及种养结合模式等方法来减少稻田温室气体排放有较好实践效应, 但不同稻田栽培环境(露地、网室)基础上的稻鸭共作对麦秸全量还田的稻田温室气体排放特征及相关土壤理化特性关联性的影响尚为少见。本研究采用裂区设计, 在两种栽培环境条件下, 以无鸭子放养的常规稻作和麦秸不还田为对照, 在等养分条件下分析麦秸全量还田与稻鸭共作模式对稻田土壤氧化还原电位、CH4排放量、产CH4潜力及CH4氧化能力、N2O排放量及N2O排放高峰期土壤反硝化酶活性、全球增温潜势、水稻产量的影响, 为稻田可持续生产和温室气体减排提供参考。结果表明, 麦秆还田增加了稻田产CH4潜力、提高了CH4排放量, 降低了稻田土壤反硝化酶活性、土壤氧化还原电位和N2O排放量, 整体上导致全球增温潜势上升96.89%~123.02%; 稻鸭共作模式, 由于鸭子的不间断活动提高了稻田土壤氧化还原电位, 降低了稻田产CH4潜力, 增强了稻田CH4氧化能力, 从而降低稻田CH4排放量, N2O排放量虽有提高, 整体上稻鸭共作模式的全球增温潜势较无鸭常规稻田下降8.72%~14.18%; 网室栽培模式显著提高了稻田土壤氧化还原电位, 降低稻田产CH4潜力、CH4氧化能力和土壤反硝化酶活性, 减少了稻田CH4和N2O排放量, 全球增温潜势降低6.35%~13.14%。本试验条件下, 稻田土壤的CH4氧化能力是产CH4潜力的2.21~3.81倍; 相同环境条件下, 稻鸭共作和麦秸还田均能增加水稻实际产量, 网室栽培的所有处理较相应的露地栽培减少了水稻实际产量1.19%~5.48%。本试验表明, 稻鸭共作和网室栽培可减缓全球增温潜势, 稻鸭共作和麦秸还田能够增加水稻实际产量。  相似文献   

17.
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.  相似文献   

18.
Abstract

Biochar application has been recognized as an effective option for promoting carbon (C) sequestration, but it may also affect the production and consumption of methane (CH4) and nitrous oxide (N2O) in soil. A 1-year field experiment was conducted to investigate the effects of rice husk charcoal application on rice (Oryza sativa L.) productivity and the balance of greenhouse gas exchanges in an Andosol paddy field. The experiment compared the treatments of rice husk charcoal applied at 10, 20 and 40 Mg ha?1 (RC10, RC20 and RC40, respectively), rice husk applied at 20 Mg ha?1 (RH20), and the control (CONT). Rice straw and grain yields did not significantly differ among the treatments. The seasonal cumulative CH4 emissions were 38–47% higher from RC10, RC20 and RC40 than from the CONT. However, the increases were not in proportion to the application rates of rice husk charcoal, and their values did not significantly differ from the CONT. On the contrary, the RH20 treatment significantly increased the cumulative CH4 emission by 227% compared to the CONT. The N2O emissions during the measurement were not affected by the treatments. As a result, the combined global warming potential (GWP) of CH4 and N2O emissions was significantly higher in RH20 than in the other treatments. There was a positive linear correlation between C storage in the top 10 cm of soil and the application rate of rice husk charcoal. The increases in soil C contents compared to the CONT corresponded to 98–149% of the C amounts added as rice husk charcoal and 41% of the C added as rice husk. Carbon dioxide (CO2) fluxes in the off season were not significantly different among RC10, RC20, RC40 and CONT, indicating that C added as rice husk charcoal remained in the soil during the fallow period. The CO2 equivalent balance between soil C sequestration and the combined GWP indicates that the rice husk charcoal treatments stored more C in soil than the CONT, whereas the RH20 emitted more C than the CONT. These results suggest that rice husk charcoal application will contribute to mitigating global warming without sacrificing rice yields.  相似文献   

19.
The change of land from natural vegetation to agricultural use causes the loss of organic carbon stored in soils and is considered as an important contributor of CO2 to the atmosphere. Four types of land use were defined in the study as: 1) natural vegetation fields (NF); 2) fuel forest, fruit tree orchards and wasteland near residential areas (FF); 3) upland crop fields (UF) and 4) paddy fields (PF). For a large area in eastern China, 416 soil species cited in the book “Soil Species of China-Volume One” were placed in one of the four use categories. Statistical results showed that organic carbon density in soil profiles 0 to 62.3 cm ranged from 3.87 to 14.25 kg m?2. Relative to NF, the loss of organic carbon in soils was correlated with human impact but varied with the type of human use. The total loss in the studied area was estimated to be 1.646 GtC. Although organic carbon in paddy soils was also significantly less than that in NF, the mean carbon density in the profile 0 to 62.3 cm was 68.1% higher than that in OF and 23.6% higher than that in FF. Therefore, flooded rice is the preferred land use type with respect to the storage of organic carbon in heavily impacted soils. On the other hand, other ecological values, e.g., biodiversity, are also affected by land use type and any change in land use should be preceded by a comprehensive review of objectives and ecological impacts.  相似文献   

20.
Groundnut as a pre‐rice crop is usually harvested 1–2 months before rice transplanting, during which much of legume residue N released could be lost. Our objectives were to investigate the effect of mixing groundnut residues (GN, 5 Mg ha?1) with rice straw (RS) in different proportions on: (i) regulating N dynamics, (ii) potential microbial interactions during decomposition, and (iii) associated nitrous oxide and methane emissions at weekly intervals during the lag phase until rice transplanting (i, ii) or harvest (iii). Decomposition was fastest in groundnut residues (64% N lost) with a negative interaction for N loss when mixed 1:1 with rice straw. Adding groundnut residues increased mineral N initially, while added rice straw led to initial microbial N immobilization. Mineral N in mixed residue treatments was significantly greatest at the beginning of rice transplanting. Soil microbial N and apparent efficiency were higher, while absolute and relative microbial C were often lowest in groundnut and mixed treatments. Microbial C:N ratio increased with increasing proportion of added rice straw. N2O losses were largest in the groundnut treatment (12.2 mg N2O‐N m?2 day?1) in the first week after residue incorporation and reduced by adding rice straw. N2O‐N emissions till rice harvest amounted to 0.73 g N2O‐N m?2 in the groundnut treatment. CH4 emissions were largest in mixed treatments (e.g. 155.9 g CH4 m?2, 1:1 treatment). Mixing residues resulted in a significant interaction in that observed gaseous losses were greater than predicted from a purely additive effect. It appears possible to regulate N dynamics by mixing rice straw with groundnut residues; however, at a trade‐off of increased CH4 emissions.  相似文献   

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