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1.
In the highlands of Madagascar, agricultural expansion gained on grasslands and cropping systems based on direct seeding with permanent vegetation cover are emerging as a means to sustain upland crop production. The objective of this study was to examine how such agricultural practices affect greenhouse‐gas emissions from a loamy Ferralsol previously used as a pasture. We conducted an experiment under controlled laboratory conditions combining cattle manure, crop residues (rice straw), and mineral fertilizers (urea plus NPK or di‐NH4‐phosphate) to mimic on‐field inputs and examined soil CO2 and N2O emissions during a 28‐d incubation at low and high water‐filled pore space (40% and 90% WFPS). Emissions of N2O from the control soil, i.e., soil receiving no input, were extremely small (< 5 ng N2O‐N (g soil)–1 h–1) even under anaerobic conditions. Soil moisture did not affect the order of magnitude of CO2 emissions while N2O fluxes were up to 46 times larger at high soil WFPS, indicating the potential influence of denitrification under these conditions. Both CO2 and N2O emissions were affected by treatments, incubation time, and their interactions. Crop‐residue application resulted in larger fluxes of CO2 but reduced N2O emissions probably due to N immobilization. The use of di‐NH4‐phosphate was a better option than NPK to reduce N2O emissions without increasing CO2 fluxes when soil received mineral fertilizers. Further studies are needed to translate the findings to field conditions and relate greenhouse‐gas budgets to crop production.  相似文献   

2.
Abstract

We studied the effect of crop residues with various C:N ratios on N2O emissions from soil. We set up five experimental plots with four types of crop residues, onion leaf (OL), soybean stem and leaf (SSL), rice straw (RS) and wheat straw (WS), and no residue (NR) on Gray Lowland soil in Mikasa, Hokkaido, Japan. The C:N ratios of these crop residues were 11.6, 14.5, 62.3, and 110, respectively. Based on the results of a questionnaire survey of farmer practices, we determined appropriate application rates: 108, 168, 110, 141 and 0 g C m?2 and 9.3, 11.6, 1.76, 1.28 and 0 g N m?2, respectively. We measured N2O, CO2 and NO fluxes using a closed chamber method. At the same time, we measured soil temperature at a depth of 5 cm, water-filled pore space (WFPS), and the concentrations of soil NH+ 4-N, NO? 3-N and water-soluble organic carbon (WSOC). Significant peaks of N2O and CO2 emissions came from OL and SSL just after application, but there were no emissions from RS, WS or NR. There was a significant relationship between N2O and CO2 emissions in each treatment except WS, and correlations between CO2 flux and temperature in RS, soil NH+ 4-N and N2O flux in SSL and NR, soil NH+ 4-N and CO2 flux in SSL, and WSOC and CO2 flux in WS. The ratio of N2O-N/NO-N increased to approximately 100 in OL and SSL as N2O emissions increased. Cumulative N2O and CO2 emissions increased as the C:N ratio decreased, but not significantly. The ratio of N2O emission to applied N ranged from ?0.43% to 0.86%, and was significantly correlated with C:N ratio (y = ?0.59 ln [x] + 2.30, r 2 = 0.99, P < 0.01). The ratio of CO2 emissions to applied C ranged from ?5.8% to 45% and was also correlated with C:N ratio, but not significantly (r 2 = 0.78, P = 0.11).  相似文献   

3.
Soil cultivation changes and usage of agricultural wastes can have profound impacts on greenhouse gas (GHG) emission from soil. In this study, the effects of soil cultivation and organic amendment on GHG emission were investigated using aerobic incubation. Surface soil (0–20 cm) from (1) rice–legume consecutive rotation (Rice) and (2) recently (<3 years) converted from rice field to plastic-covered intensive vegetable and flower production (VegC) were collected in Kunming, P.R. China. Rose (Rosa rugosa Thunb.) residues and cattle manure were applied at 5% by weight. Results indicated that N2O and CO2 fluxes were significantly influenced by soil cultivation, organic amendment, incubation time and their interaction (p <0.05). Applying cattle manure increased, while rose residue decreased, cumulative N2O emissions from soil (84 days). Rose residue application significantly increased cumulative CO2 emissions with peak values of 6371 (Rice) and 7481 mg kg?1 (VegC), followed by cattle manure addition figure of 2265 (VegC) and 3581 mg kg?1 (Rice). Both were significantly higher (p <0.05) than the un-amended Control at 709 (VegC) and 904 mg kg?1 (Rice). Our study demonstrates that a low C/N ratio in cattle manure is better than a high C/N ratio in rose residue in regard to reducing the global warming potential of agricultural soil.  相似文献   

4.
Application of crop residues and its biochar produced through slow pyrolysis can potentially increase carbon (C) sequestration in agricultural production systems. The impact of crop residue and its biochar addition on greenhouse gas emission rates and the associated changes of soil gross N transformation rates in agricultural soils are poorly understood. We evaluated the effect of wheat straw and its biochar applied to a Black Chernozemic soil planted to barley, two growing seasons or 15 months (at the full-bloom stage of barley in the second growing season) after their field application, on CO2 and N2O emission rates, soil inorganic N and soil gross N transformation rates in a laboratory incubation experiment. Gross N transformation rates were studied using the 15N isotope pool dilution method. The field experiment included four treatments: control, addition of wheat straw (30 t ha?1), addition of biochar pyrolyzed from wheat straw (20 t ha?1), and addition of wheat straw plus its biochar (30 t ha?1 wheat straw + 20 t ha?1 biochar). Fifteen months after their application, wheat straw and its biochar addition increased soil total organic C concentrations (p?=?0.039 and <0.001, respectively) but did not affect soil dissolved organic C, total N and NH4 +-N concentrations, and soil pH. Biochar addition increased soil NO3 ?-N concentrations (p?=?0.004). Soil CO2 and N2O emission rates were increased by 40 (p?p?=?0.03), respectively, after wheat straw addition, but were not affected by biochar application. Straw and its biochar addition did not affect gross and net N mineralization rates or net nitrification rates. However, biochar addition doubled gross nitrification rates relative to the control (p?2 and N2O emissions and enhance soil C sequestration. However, the implications of the increased soil gross nitrification rate and NO3 ?-N in the biochar addition treatment for long-term NO3 ?-N dynamics and N2O emissions need to be further studied.  相似文献   

5.
Experiments were conducted in an attempt to study the impact of using different organic residues as fertilizers on grain yield, magnitude of nitrous oxide (N2O) emissions, and soil characteristics. Five fertilizer treatments including conventional nitrogen (N) fertilizer, cow manure, rice straw, poultry manure, and sugarcane bagasse were applied in the rice field in 2012. The maximum reduction in seasonal N2O emissions (10–27%) was observed under the influence of rice straw application over conventional N fertilizer. The experiment was repeated for a second season in 2013 with the same treatments for further confirmation of the results obtained during the first year of experimentation. The application of rice straw also showed a slight advantage by increasing grain yield (4.38 t ha?1) compared to control. Important soil properties and plant growth parameters were studied and their relationships with N2O emission were worked out. The incorporation of organic residues helped in restoring and improving the soil health and effectively enhancing grain yield with reduced N2O emission from rice fields.  相似文献   

6.
Proper rice straw management in paddy fields is necessary in order to sustain soil productivity and reduce greenhouse gas emissions. A field experiment was carried out from 2008 to 2011 in subtropical China: (1) to monitor rice yield, soil available nutrients, CH4, and N2O emissions and (2) to evaluate the effects of timing of rice straw incorporation and joint N application rate in a double rice cropping system. The total amount of rice straw from one cropping season was incorporated in winter (WS) or in spring (SS) and mineral N was jointly applied with rice straw incorporation at rates of 0, 30, and 60 % of the basal fertilization rate (N0B, N30B, and N60B) for the first rice crop. Soil water was naturally drained during the period of winter fallow (PWF) and controlled under intermittent irrigation during the period of first rice growth (PFR). Compared with SS, WS significantly (P?<?0.05) increased the first rice yield only in the flooding year (2010), and increased the soil available K concentration after PWF and PFR in 2008–2009 and the hydrolysable N concentration after PWF in 2010–2011. Meanwhile, WS significantly decreased the total CH4 emission by about 12 % in 2009–2010 and 2010–2011, but increased the total N2O emission by 15–43 % particularly during PWF in all 3 years, resulting in a lower GWP in WS in the flooding year and no differences in the nonflooding years. Compared with N0B, joint N application (N60B and N30B) increased the soil hydrolysable N after PWF in all 3 years. Meanwhile, it decreased the total CH4 emissions by 21 % and increased the N2O emissions during PWF by 75–150 % in the nonflooding years, but the net GWP was lower in N60B than in N0B. The results suggested that the rice straw incorporation with joint N application in winter is more sustainable compared with the local practices such as rice straw incorporation in spring or open-field burning.  相似文献   

7.
To investigate the influence of plant residues decomposition on N2O emission, laboratory incubations were carried out for a period of 21 days using urea and five plant residues with a wide range of C:N ratios from 8 to 118. Incorporation of plant residues enhanced N2O and CO2 emissions. The two gas fluxes were significantly correlated (R2=0.775, p<0.001). Cumulative emissions of N2O and CO2 were negatively correlated with the C:N ratio in plant residues (R2=0.783 and 0.986 for N2O, and 0.854 for CO2, respectively). A negative relationship between the N2O-N/NO3−-N ratio and the C:N ratio was observed (R2=0.867) when residue plus urea was added. We calculated the changes in dissolved organic C (DOC) and the relevant changes in N2O emission. The incorporation of residues increased DOC when compared with the control, while the incorporation of residue plus urea decreased DOC. Cumulative emissions of N2O and CO2 were positively correlated with DOC concentration measured at the end of the incubation. In addition, the N2O emission fraction, defined as N2O-N emissions per unit N input, was not found to be a constant for either residue-N or urea-N amendment but dependent on C:N ratio when plant residue was incorporated.  相似文献   

8.
Since the development of effective N2O mitigation options is a key challenge for future agricultural practice, we studied the interactive effect of tillage systems on fertilizer-derived N2O emissions and the abundance of microbial communities involved in N2O production and reduction. Soil samples from 0–10 cm and 10–20 cm depth of reduced tillage and ploughed plots were incubated with dairy slurry (SL) and manure compost (MC) in comparison with calcium ammonium nitrate (CAN) and an unfertilized control (ZERO) for 42 days. N2O and CO2 fluxes, ammonium, nitrate, dissolved organic C, and functional gene abundances (16S rRNA gene, nirK, nirS, nosZ, bacterial and archaeal amoA) were regularly monitored. Averaged across all soil samples, N2O emissions decreased in the order CAN and SL (CAN?=?748.8?±?206.3, SL?=?489.4?±?107.2 μg kg?1) followed by MC (284.2?±?67.3 μg kg?1) and ZERO (29.1?±?5.9 μg kg?1). Highest cumulative N2O emissions were found in 10–20 cm of the reduced tilled soil in CAN and SL. N2O fluxes were assigned to ammonium as source in CAN and SL and correlated positively to bacterial amoA abundances. Additionally, nosZ abundances correlated negatively to N2O fluxes in the organic fertilizer treatments. Soils showed a gradient in soil organic C, 16S rRNA, nirK, and nosZ with greater amounts in the 0–10 than 10–20 cm layer. Abundances of bacterial and archaeal amoA were higher in reduced tilled soil compared to ploughed soils. The study highlights that tillage system induced biophysicochemical stratification impacts net N2O emissions within the soil profile according to N and C species added during fertilization.  相似文献   

9.
Agricultural fields, including rice (Oryza sativa L.) paddy fields, constitute one of the major sources of atmospheric methane (CH4) and nitrous oxide (N2O). Organic matter application, such as straw and organic fertilizer, enhances CH4 emission from paddy fields. In addition, rice straw management after harvest regulates CH4 emissions in the growing season. The interaction of tillage times and organic fertilizer application on CH4 and N2O emissions is largely unknown. Therefore, we studied the effects of fallow-season tillage times and fertilizer types on CH4 and N2O emissions in paddy fields in Ehime, southwestern Japan. From November 2011 to October 2013, four treatments, two (autumn and spring) or one (spring) in the first year, or two (autumn and spring) or three (autumn, winter, and spring) in the second year times of tillage with chemical or organic fertilizer application, were established. Gas fluxes were measured by the closed-chamber method. Increasing the number of tillage times from one to two decreased succeeding CH4 emission and the emission factor for CH4 (EFCH4) in the rice-growing season, suggesting that the substrate for CH4 production was reduced by autumn and spring tillage in the fallow season. Higher EFCH4 [1.8–2.0 kg carbon (C) ha?1 d?1] was observed when more straw was applied (6.9–7.2 Mg ha?1) in the second year. Organic fertilizer application induced higher CH4 emission just after the application as basal and supplemental fertilizers, especially at a lower straw application rate. This indicated that EFCH4 in the organically managed fields should be determined individually. Organic fertilizer application with two tillage times induced N2O efflux during the rice-growing season in the second year, but N2O emissions were not affected by winter tillage. Although paddy fields can act as an N2O sink because of reduced soil conditions when straw application was high, application of organic C and nitrogen as fertilizer can enhance N2O production by the denitrification process during the growing season, especially in the ripening stage when soil anaerobic conditions became moderate. These results suggest that negative emission factors for N2O (EFN2O) can be applied, and EFN2O of organic fertilizer should be considered during the estimation of N2O emission in the paddy field.  相似文献   

10.
This study evaluated the effects of rice straw and water regimes on CH4 and N2O emissions from paddy fields for two rice growing seasons (summer 2014 and spring 2015). Water regimes included alternating wet–dry irrigation (AWD) maintained at three levels (–5 cm, – 10 cm and –15 cm) in comparison to continuous flooding irrigation (CF). Rice straw (5 t ha–1) was incorporated into the top soil (0 – 15 cm), distributed and burned in situ. Results showed that using burned in situ rice straw was found to reduce seasonal cumulative CH4 emission (24–34% in summer; 18–28% in spring), N2O emission (21–32% in summer; 22–29% in spring) and lower rice yield (8–9%) than rice straw incorporation into top soil. AWD methods reduced the amount of CH4 production (22.6–41.5%) and increased N2O emission (25–26%) without any decrease in rice yield. Rice straw incorporation into the top soil with AWD had higher water productivity (23–37%) than rice straw when burned in situ with CF. The results conclude that AWD and rice straw management can be employed as mitigation strategy for CH4 and N2O emissions from paddy fields in Central Vietnam.  相似文献   

11.
Global warming potential (GWP) of sandy paddy soils may be reduced by trade-offs between N2O, CH4 and CO2 emissions. Laboratory experiments using either rice straw (1% or 0.5%) or together with urea-N (25 or 50 mg N kg−1 soil) at various levels of soil water were carried out for 30 days each, to test this assumption. Waterlogging combined with urea-N increased total N2O emissions, with greater release upon rewaterlogging (7.4 mg N kg−1 soil) than experienced by removing waterlogging only. Rice straw±urea-N either emitted small amounts of N2O or resulted in negative values at all water levels, including saturated and aerobic. Total CH4 fluxes declined with the decreased water levels and amount of rice straw (<193 mg C kg−1 soil), and also for CO2 with the latter (<1340 mg C kg−1 soil), and rewaterlogging had little influence on both. N2O under rewaterlogged and waterlogged±urea-N, CH4 under waterlogged with rice straw, and CO2 for the remainder were the major contributors to GWP. Results show that waterlogging following aerobic decomposition of rice straw (1%) with urea-N, applied either at the beginning or at the end of the aerobic conditions, could decrease GWP by 56-64% and 32-42% over the sole addition of rice straw (1% and 0.5%) under waterlogged and saturated conditions, respectively.  相似文献   

12.
In the context of sustainable soil-quality management and mitigating global warming, the impacts of incorporating raw or field-burned adzuki bean (Vigna angularis (Willd.) Ohwi & Ohashi) and wheat (Triticum aestivum L.) straw residues on carbon dioxide (CO2) and nitrous oxide (N2O) emission rates from soil were assessed in an Andosol field in northern Japan. Losses of carbon (C) and nitrogen (N) in residue biomass during field burning were much greater from adzuki bean residue (98.6% of C and 98.1% of N) than from wheat straw (85.3% and 75.3%, respectively). Although we noted considerable inputs of carbon (499 ± 119 kg C ha–1) and nitrogen (5.97 ± 0.76 kg N ha–1) from burned wheat straw into the soil, neither CO2 nor N2O emission rates from soil (over 210 d) increased significantly after the incorporation of field-burned wheat straw. Thus, the field-burned wheat straw contained organic carbon fractions that were more resistant to decomposition in soil in comparison with the unburned wheat straw. Our results and previously reported rates of CO2, methane (CH4) and N2O emission during wheat straw burning showed that CO2-equivalent greenhouse gas emissions under raw residue incorporation were similar to or slightly higher than those under burned residue incorporation when emission rates were assessed during residue burning and after subsequent soil incorporation.  相似文献   

13.
A laboratory investigation was performed to compare the fluxes of dinitrogen (N2), N2O and carbon dioxide (CO2) from no-till (NT) and conventional till (CT) soils under the same water, mineral nitrogen and temperature status. Intact soil cores (0-10 cm) were incubated for 2 weeks at 25 °C at either 75% or 60% water-filled pore space (WFPS) with 15N-labeled fertilizers (100 mg N kg−1 soil). Gas and soil samples were collected at 1-4 day intervals during the incubation period. The N2O and CO2 fluxes were measured by a gas chromatography (GC) system while total N2 and N2O losses and their 15N mole fractions in the soil mineral N pool were determined by a mass spectrometer. The daily accumulative fluxes of N2 and N2O were significantly affected by tillage, N source and soil moisture. We observed higher (P<0.05) fluxes of N2+N2O, N2O and CO2 from the NT soils than from the CT soils. Compared with the addition of nitrate (NO3−), the addition of ammonium (NH4+) enhanced the emissions of these N and C gases in the CT and NT soils, but the effect of NH4+ on the N2 and/or N2O fluxes was evident only at 60% WFPS, indicating that nitrification and subsequent denitrification contributed largely to the gaseous N losses and N2O emission under the lower moisture condition. Total and fertilizer-induced emissions of N2 and/or N2O were higher (P<0.05) at 75% WFPS than with 60% WFPS, while CO2 fluxes were not influenced by the two moisture levels. These laboratory results indicate that there is greater potential for N2O loss from NT soils than CT soils. Avoiding wet soil conditions (>60% WFPS) and applying a NO3− form of N fertilizer would reduce potential N2O emissions from arable soils.  相似文献   

14.
Elevated CO2(eCO2) and rice cultivars can strongly alter CH4 and N2 O emissions from paddy fields.However,detailed information on how their interaction affects greenhouse gas fluxes in the field is still lacking.In this study,we investigated CH4 and N2 O emissions and rice growth under two contrasting rice cultivars(the strongly and weakly responsive cultivars) in response to eCO2,200 μmol mol-1 higher than the ambient ...  相似文献   

15.
The DNDC (DeNitrification-DeComposition)-Rice model, one of the most advanced process-based models for the estimation of greenhouse gas emissions from paddy fields, has been discussed mostly in terms of the reproducibility of observed methane (CH4) emissions from Japanese rice paddies, but the model has not yet been validated for tropical rice paddies under alternate wetting and drying (AWD) irrigation management, a water-saving technique. We validated the model by using CH4 and nitrous oxide (N2O) flux data from rice in pots cultivated under AWD irrigation management in a screen-house at the International Rice Research Institute (Los Baños, the Philippines). After minor modification and adjustment of the model to the experimental irrigation conditions, we calculated grain yield and straw production. The observed mean daily CH4 fluxes from the continuous flooding (CF) and AWD pots were 4.49 and 1.22?kg?C?ha?1?day?1, respectively, and the observed mean daily N2O fluxes from the pots were 0.105 and 34.1?g?N?ha?1?day?1, respectively. The root-mean-square errors, indicators of simulation error, of daily CH4 fluxes from CF and AWD pots were calculated as 1.76 and 1.86?kg?C?ha?1?day?1, respectively, and those of daily N2O fluxes were 2.23 and 124?g?N?ha?1?day?1, respectively. The simulated gross CH4 emissions for CF and AWD from the puddling stage (2 days before transplanting) to harvest (97 days after transplanting) were 417 and 126?kg?C?ha?1, respectively; these values were 9.8% lower and 0.76% higher, respectively, than the observed values. The simulated gross N2O emissions during the same period were 0.0279 and 1.45?kg?N?ha?1 for CF and AWD, respectively; these values were respectively 87% and 29% lower than the observed values. The observed total global warming potential (GWP) of AWD resulting from the CH4 and N2O emissions was approximately one-third of that in the CF treatment. The simulated GWPs of both CF and AWD were close to the observed values despite the discrepancy in N2O emissions, because N2O emissions contributed much less than CH4 emissions to the total GWP. These results suggest that the DNDC-Rice model can be used to estimate CH4 emission and total GWP from tropical paddy fields under both CF and AWD conditions.  相似文献   

16.
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   

17.
The net effect of no-till techniques on nitrous oxide (N2O) emissions is inconsistent and poorly quantified in comparison to conventionally tilled farming. This study assesses N2O emissions and yields from paddy fields during the wheat-growing season under conventional and no-till farming, as well as mitigation of N2O evolution using dicyandiamide and chlorinated pyridine (CP) as nitrification inhibitor (NI). Both tillage practices and NIs significantly (P?<?0.01) affected cumulative N2O emissions and yields. In comparison to conventional tillage, the cumulative N2O emissions under no-till farming were increased by 8.2–19.3 % and the water-filled pore space was higher on most days. Relative to no-tillage, the conventional tillage averagely increased the wheat yield by 6.0 % and reduced yield-scaled N2O–N emission by 44.5 %. The two NIs averagely increased the wheat yield by 9.7 % and reduced yield-scaled N2O–N emission by 67.7 %. The treatment with CP produced the highest yield with the lowest N2O emissions, thus leading to the lowest yield-scaled N2O–N emission (0.15–0.17 kg N2O–N t?1 grain yield) under both tillage practices.  相似文献   

18.
Yak and Tibetan sheep graze extensively on natural grasslands in the Qinghai-Tibetan Plateau, and large amounts of excrement are directly deposited onto alpine grasslands. However, information on greenhouse gas (GHG) emissions from this excrement is limited. This study evaluated the short-term effects of yak and Tibetan sheep dung on nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) emissions from alpine steppe soil at a water holding capacity (WHC) of 40 or 60 % and from alpine meadow soil at a WHC of 60 or 80 % under laboratory conditions. Cumulative N2O emissions over a 15-day incubation period at low soil moisture conditions ranged from 111 to 232 μg N2O–N kg soil?1 in the yak dung treatments, significantly (P?<?0.01) higher than that of sheep dung treatments (28.7 to 33.7 μg N2O–N kg soil?1) and untreated soils (1.04–6.94 μg N2O–N kg soil?1). At high soil moisture conditions, N2O emissions were higher from sheep dung than yak dung and non-treated soils. No significant difference was found between the yak dung and non-treated alpine meadow soil at 80 % WHC. Low N2O emission in the yak dung treatment from relatively wet soil was probably due to complete denitrification to N2. Yak dung markedly (P?<?0.001) increased CH4 and CO2 emissions, likely being the main source of these two gases. The addition of sheep dung markedly (P?<?0.001) elevated CO2 emissions. Dung application significantly (P?<?0.01) increased global warming potential, particularly for alpine steppe soil. In conclusion, our findings suggest that yak and Tibetan sheep dung deposited on alpine grassland soils may increase GHG emissions.  相似文献   

19.
The application of nitrogen (N) fertilizers and liming (CaCO3) to improve soil quality and crop productivity are regarded as effective and important agricultural practices. However, they may increase greenhouse gas (GHG) emissions. There is limited information on the GHG emissions of tropical soils, specifically when liming is combined with N fertilization. We therefore conducted a full factorial laboratory incubation experiment to investigate how N fertilizer (0 kg N ha−1, 12.5 kg N ha−1 and 50 kg N ha−1) and liming (target pH = 6.5) affect GHG emissions and soil N availability. We focussed on three common acidic soils (two ferralsols and one vertisol) from Lake Victoria (Kenya). After 8 weeks, the most significant increase in cumulative carbon dioxide (CO2) and nitrous oxide (N2O) fluxes compared with the unfertilized control was found for the two ferralsols in the N + lime treatment, with five to six times higher CO2 fluxes than the control. The δ13C signature of soil-emitted CO2 revealed that for the ferralsols, liming (i.e. the addition of CaCO3) was the dominant source of CO2, followed by urea (N fertilization), whereas no significant effect of liming or of N fertilization on CO2 flux was found for the vertisol. In addition, the N2O fluxes were most significantly increased by the high N + lime treatment in the two ferralsols, with four times and 13 times greater N2O flux than that of the control. No treatment effects on N2O fluxes were observed for the vertisol. Liming in combination with N fertilization significantly increased the final nitrate content by 14.5%–39% compared with N fertilization alone in all treatment combinations and soils. We conclude that consideration should be given to the GHG budgets of agricultural ferralsols since liming is associated with high liming-induced CO2 and N2O emissions. Therefore, nature-based and sustainable sources should be explored as an alternative to liming in order to manage the pH and the associated fertility of acidic tropical soils.  相似文献   

20.
CO2 and N2O are important greenhouse gases that are related to soil mineralization–immobilization turnover and nitrification. To explore the responses of CO2 and N2O emissions to N deposition in forests with different N transformation characteristics, CO2 and N2O fluxes were measured in two NH4NO3 fertilized plots. One plot was in a temperate pine plantation in Heilongjiang Liangshui National Nature Reserve (LS) with slow and minimally coupled mineralization–immobilization turnover and a high nitrification rate. The other plot was in a subtropical bamboo forest in the Fujian Daiyun Mountain National Nature Reserve (DY) in China with rapid and coupled mineralization–immobilization turnover but a low nitrification rate. The results showed that CO2 emissions in the DY with a high mineralization rate were greater than those in the LS. Cumulative CO2 emissions were significantly enhanced by N addition in DY, but in LS, they were not affected. The mean N2O fluxes in the control were 0.010 and 0.008 mg N m?2 hr?1 for LS and DY, respectively. High N addition stimulated N2O emissions in both LS and DY, but the response ratio for N2O flux in LS (8.6) was larger than that in DY (2.9). These results suggested that soils with rapid and coupled mineralization–immobilization turnover are beneficial to CO2 emissions and their positive response to N deposition. A high nitrification rate contributed to high N2O emissions and the sensitive response of N2O emissions to N deposition.  相似文献   

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