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1.
The objective of this work was to evaluate the effect of the chemical nature and application frequency of N fertilizers at different moisture contents on soil N2O emissions and N2O/(N2O+N2) ratio. The research was based on five fertilization treatments: unfertilized control, a single application of 80 kg ha−1 N-urea, five split applications of 16 kg ha−1 N-urea, a single application of 80 kg ha−1 N–KNO3, five split applications of 16 kg ha−1 N–KNO3. Cumulative N2O emissions for 22 days were unaffected by fertilization treatments at 32% water-filled pore space (WFPS). At 100% and 120% WFPS, cumulative N2O emissions were highest from soil fertilized with KNO3. The split application of N fertilizers decreased N2O emissions compared to a single initial application only when KNO3 was applied to a saturated soil, at 100% WFPS. Emissions of N2O were very low after the application of urea, similar to those found at unfertilized soil. Average N2O/(N2O+N2) ratio values were significantly affected by moisture levels (p = 0.015), being the lowest at 120% WFPS. The N2O/(N2O+N2) ratio averaged 0.2 in unfertilized soil and 0.5 in fertilized soil, although these differences were not statistically significant.  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.
In this study, we investigated N2O emissions from two fields under minimum tillage, cropped with maize (MT maize) and summer oats (MT oats), and a conventionally tilled field cropped with maize (CT maize). Nitrous oxide losses from the MT maize and MT oats fields (5.27 and 3.64 kg N2O-N ha−1, respectively) were significantly higher than those from the CT maize field (0.27 kg N2O-N ha−1) over a period of 1 year. The lower moisture content in CT maize (43% water-filled pore space [WFPS] compared to 60–65%) probably caused the difference in total N2O emissions. Denitrification was found to be the major source of N2O loss. Emission factors calculated from the MT field data were high (0.04) compared to the CT field (0.001). All data were simulated with the denitrification decomposition model (DNDC). For the CT field, N2O and N2O + N2 emissions were largely overestimated. For the MT fields, there was a better agreement with the total N2O and N2O + N2 emissions, although the N2O emissions from the MT maize field were underestimated. The simulated N2O emissions were particularly influenced by fertilization, but several other measured N2O emission peaks associated with other management practices at higher WFPS were not captured by the model. Several mismatches between simulated and measured \textNH4+ {\text{NH}}_4^ + , \textNO3- {\text{NO}}_3^ - and WFPS for all fields were observed. These mismatches together with the insensitivity of the DNDC model for increased N2O emissions at the management practices different from fertilizer application explain the limited similarity between the simulated and measured N2O emissions pattern from the MT fields.  相似文献   

4.

Purpose

Nitrification and denitrification processes dominate nitrous oxide (N2O) emission in grassland ecosystems, but their relative contribution as well as the abiotic factors are still not well understood.

Materials and methods

Two grassland soils from Duolun in Inner Mongolia, China, and Canterbury in New Zealand were used to quantitatively compare N2O production and the abundance of bacterial and archaeal amoA, denitrifying nirK and nirS genes in response to N additions (0 and 100 μg NH4 +–N g?1 dry soil) and two soil moisture levels (40 and 80 % water holding capacity) using microcosms.

Results and discussion

Soil moisture rather than N availability significantly increased the nitrification rate in the Duolun soil but not in the Canterbury soil. Moreover, N addition promoted denitrification enzyme activities in the Canterbury soil but not in the Duolun soil. The abundance of bacterial and archaeal amoA genes significantly increased as soil moisture increased in the Duolun soil, whereas in the Canterbury soil, only the abundance of bacterial amoA gene increased. The increase in N2O flux induced by N addition was significantly greater in the Duolun soil than in the Canterbury soil, suggesting that nitrification may have a dominant role in N2O emission for the Duolun soil, while denitrification for the Canterbury soil.

Conclusions

Microbial processes controlling N2O emission differed in grassland soils, thus providing important baseline data in terms of global change.
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5.
Nitrous oxide (N2O) contributes to greenhouse effect; however, little information on the consequences of different moisture levels on N2O/(N2O+N2) ratio is available. The aim of this work was to analyze the influence of different soil moisture values and thus of redox conditions on absolute and relative emissions of N2O and N2 at intact soil cores from a Vertic Argiudoll. For this reason, the effect of water-filled porosity space (WFPS) values of soil cores of 40, 80,100, and 120% (the last one with a 2-cm surface water layer) was investigated. The greatest N2O emission occurred at 80% WFPS treatment where conditions were not reductive enough to allow the complete reduction to N2. The N2O/(N2O+N2) ratio was lowest (0–0.051) under 120% WFPS and increased with decreasing soil moisture content. N2O/(N2O+N2) ratio values significantly correlated with soil Eh; redox conditions seemed to control the proportion of N gases emitted as N2O. N2O emissions did not correlate satisfactorily with N2O/(N2O+N2) ratio values, whereas they were significantly explained by the amount of total N2O+N2 emissions.  相似文献   

6.
Cultivation of rice in unsaturated soils covered with mulch is receiving more attention in China because of increasingly serious water shortage; however, greenhouse gas emission from this cultivation system is still poorly understood. A field experiment was conducted in 2001 to compare nitrous oxide (N2O) and methane (CH4) emission from rice cultivated in unsaturated soil covered with plastic or straw mulch and the traditional waterlogged production system. Trace gas fluxes from the soil were measured weekly throughout the entire growth period using a closed chamber method. Nitrous oxide emissions from unsaturated rice fields were large and varied considerably during the rice season. They were significantly affected by N fertilizer application rate. In contrast, N2O emission from the waterlogged system was very low with a maximum of 0.28 mg N2O m–2 h–1. However, CH4 emission from the waterlogged system was significantly higher than from the unsaturated system, with a maximum emission rate of 5.01 mg CH4 m–2 h–1. Our results suggested that unsaturated rice cultivation with straw mulch reduce greenhouse gas emissions.  相似文献   

7.
Even if it is less polluting than other farm sectors, grape growing management has to adopt measures to mitigate greenhouse gas (GHG) emissions and to preserve the quality of grapevine by-products. In viticulture, by land and crop management, GHG emissions can be reduced through adjusting methods of tillage, fertilizing, harvesting, irrigation, vineyard maintenance, electricity, natural gas, and transport until wine marketing, etc. Besides CO2, nitrous oxide (N2O) and methane (CH4), released from fertilizers and waste/wastewater management are produced in vineyards. As the main GHG in vineyards, N2O can have the same harmful action like large quantities of CO2. Carbon can be found in grape leaves, shoots, and even in fruit pulp, roots, canes, trunk, or soil organic matter. C sequestration in soil by using less tillage and tractor passing is one of the efficient methods to reduce GHG in vineyards, with the inconvenience that many years are needed for detectable changes. In the last decades, among other methods, cover crops have been used as one of the most efficient way to reduce GHG emissions and increase fertility in vineyards. Even if we analyze many references, there are still limited information on practical methods in reducing emissions of greenhouse gases in viticulture. The aim of the paper is to review the main GHG emissions produced in vineyards and the approached methods for their reduction, in order to maintain the quality of grapes and other by-products.  相似文献   

8.
A field study was conducted to investigate the long-term effect of surface application of sewage sludge composts vs chemical N fertilizer on total N, total C, soluble organic C, pH, EC, microbial biomass C and N, protease activity, deaminase activity, urease activity, gross and net rates of N mineralization and nitrification, CO2 evolution, and N2O production. Soil samples were taken from five depths (0–15, 15–20, 20–30, 30–40, and 40–50 cm) of a long-term experiment at the University of Tokyo, Japan. Three fields have been receiving sewage sludge composted with rice husk (RH), sawdust (SD), or mixed chemical fertilizer NPK (CF), applied at the rate of 240 kg N ha–1 each in split applications in summer and autumn since 1978. Significantly higher amounts of total N and C and soluble organic C were found in the compost than in the CF treatments up to the 40-cm soil depth, indicating improved soil quality in the former. In the CF treatment, soil pH values were significantly lower and electrical conductivity values were significantly higher than those of compost-treated soils of up to 50 cm depth. Soil microbial biomass C and N, CO2 evolution, protease, deaminase, and urease activities were significantly higher in the compost than in the CF treatments due to greater availability of organic substrates that stimulated microbial activity. Gross N mineralization rates determined by 15N dilution technique were eight and five times higher in the SD and RH treatments than in the CF treatment, respectively, probably due to high levels of microbial and enzyme activities. Net N mineralization rates were also significantly higher in the compost treatments and were negative in the CF treatment indicating immobilization. Net nitrification rates were higher in compost treatments and negative in the CF treatment. Nitrous oxide productions from compost treatments were higher than the CF treatment due to the greater availability of mineral N as a result of higher mineralization and nitrification rates and soluble organic C in the former. Most of the measured parameters were highest in the surface soil (0–15 cm) and were significantly higher in the SD treatment than in the RH treatment.  相似文献   

9.
Alpine grasslands with a high soil organic carbon(SOC) storage on the Tibetan Plateau are experiencing rapid climate warming and anthropogenic nitrogen(N) deposition; this is expected to substantially increase the soil N availability, which may impact carbon(C) cycling. However, little is known regarding how N enrichment influences soil microbial communities and functions relative to C cycling in this region. We conducted a 4-year field experiment on an alpine grassland to evaluate the effects o...  相似文献   

10.
11.
The only known sink for nitrous oxide (N2O) is biochemical reduction to dinitrogen (N2) by N2O reductase (N2OR). We hypothesized that the application of N2O-reducing denitrifier-inoculated organic fertilizer could enhance soil N2O consumption while the disruption of nosZ genes could result in inactivation of N2O consumption. To test such hypotheses, a denitrifier-inoculated granular organic fertilizer was applied to both soil microcosms and fields. Of 41 denitrifier strains, 38 generated 30N2 in the end products of denitrification (30N2 and 46N2O) after the addition of Na15NO3 in culture condition, indicating their high N2O reductase activities. Of these 41 strains, 18 were screened in soil microcosms after their inoculation into the organic fertilizer, most of which were affiliated with Azospirillum and Herbaspirillum. These 18 strains were nutritionally starved to improve their survival in soil, and 14 starved and/or non-starved strains significantly decreased N2O emissions in soil microcosms. However, the N2O emission had not been decreased in soil microcosms after inoculating with a nosZ gene-disruptive strain, suggesting that N2O reductase activity might be essential for N2O consumption. Although the decrease of N2O was not significant at field scales, the application of organic fertilizer inoculated with Azospirillum sp. TSH100 and Herbaspirillum sp. UKPF54 had decreased the N2O emissions by 36.7% in Fluvisol and 23.4% in Andosol in 2014, but by 21.6% in Andosol in 2015 (H. sp. UKPF54 only). These results suggest that the application of N2O-reducing denitrifier-inoculated organic fertilizer may enhance N2O consumption or decrease N2O emissions in agricultural soils.  相似文献   

12.
The contributions of root and microbial respiration to the CO2 emission from the surface of gray forest and soddy-podzolic soils under meadow and forest vegetation were determined in field and laboratory experiments. In the field, a new modification of the substrate-induced respiration (SIR) method was applied. According to this method, the contribution of root respiration was estimated at 41–50% for meadow cenoses and 33% for forest cenoses; similar values were obtained in the course of separate incubation of roots and soil in laboratory (42–57% and 29–32%, respectively) and with the use of the laboratory version of the SIR method (35–40% and 21–31%, respectively). The analysis of difference between the values of root respiration and microbial respiration obtained by the field and laboratory methods for the same experimental plots and the comparison of advantages and disadvantages of these methods made it possible to outline the ways for the further improvement of the field version of the SIR method.  相似文献   

13.
At cattle overwintering areas, inputs of nutrients in animal excrements create conditions favourable for intensive microbial activity in soil. During nitrogen transformations, significant amounts of N2O are released, which makes overwintering areas important sources of N2O emission. In previous studies, however, increasing intensity of long-term cattle impact did not always increase emissions of N2O from the soil: in some cases, N2O emissions from the soil were lower at the most impacted area than at the moderately impacted one. Thus, the relationships between the level of long-term animal impact and potential production of N2O from soil by denitrification were investigated in field and laboratory experiments. Field measurements indicated that the production of N2O after glucose and nitrate amendments was greater in severely and moderately impacted locations than in an unimpacted location, while differences between the severely and moderately impacted locations were not significant. In laboratory experiments, the potential production of N2O (measured as anaerobic production of N2O after addition of glucose and nitrate) was highest in the moderately impacted soil. Surprisingly, potential N2O production was lower in the most impacted than in the moderately impacted soil, and the net N2O production in the highly impacted soil was further decreased by a significant reduction of N2O to N2. The expected stimulating effect of an increasing ratio of glucose C to nitrate N on the reduction of N2O to N2 during denitrification was not confirmed. The results show that cattle increase the denitrification potential of the soil but suggest that the denitrification potential does not increase indefinitely with increasing cattle impact.  相似文献   

14.
The effect of the temperature and moisture on the emission of N2O from arable soils was studied in model experiments with arable soils at three contrasting levels of wetting and in a wide temperature range (from −5 to +25°C), including freeze-thaw cycles. It was shown that the losses of fertilizer nitrogen from the soils with water contents corresponding to 60 and 75% of the total water capacity (TWC) did not exceed 0.01–0.09% in the entire temperature range. In the soils with an elevated water content (90% of the TWC) at 25°C, the loss of fertilizer nitrogen in the form of N2O reached 2.35% because of the active denitrification. The extra N2O flux initiated by the freeze-thaw processes made up 88–98% of the total nitrous oxide flux during the entire experiment.  相似文献   

15.

Purpose

Ecosystem restorations can impact carbon dioxide (CO2) and nitrous oxide (N2O) emissions which are important greenhouse gasses. Alpine meadows are degraded worldwide, but restorations are increasing. Because their soils represent large carbon (C) and nitrogen (N) pools, they may produce significant amounts of CO2 and N2O depending on the plant species used in restorations. In addition, warming and N deposition may impact soil CO2 and N2O emissions from restored meadows.

Materials and methods

We collected soils from degraded meadows and plots restored using three different plant species at Wugong Mountain (Jiangxi, China). We measured CO2 and N2O emissions when soils were incubated at different temperatures (15, 25 or 35 °C) and levels of N addition (control vs. 4 g m?2) to understand their responses to warming and N deposition.

Results and discussion

Dissolved organic C was higher in restored plots (especially with Fimbristylis dichotoma) compared to non-restored bare soils, and their soil inorganic N was lower. CO2 emission rates were increased by vegetation restorations, decreased by N deposition, and increased by warming. CO2 emission rates were similar for the three grass species at 15 and 25 °C, but they were lower with Miscanthus floridulus at 35 °C. Soils from F. dichotoma and Carex chinensis plots had higher N2O emissions than degraded or M. floridulus plots, especially at 25 °C.

Conclusions

These results show that the effects of restorations on soil greenhouse gas emissions depended on plant species. In addition, these differences varied with temperature suggesting that future climate should be considered when choosing plant species in restorations to predict soil CO2 and N2O emissions and global warming potential.
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16.
The effects of intense moistening and alternating freezing-thawing cycles on the N2O emission from soils of an oak forest (brown forest soil in Lower Saxony, Germany) and southern tundra (cryozem in the area of Tal’nik Station near the city of Vorkuta) were studied in a model experiment. A sharp rise in the N2O emission reaching 350–670 μg N/m2 per h was recorded during the thawing of the brown forest soil, and the loss of nitrogen initiated by the freezing-thawing cycles comprised 74% of the total N2O emission during the whole experiment. No significant fluxes of N2O from the tundra soil were recorded during the experiment.  相似文献   

17.
The influence of crop residues with different C: N ratios on the N2O emission from differently managed loamy sand soddy-podzolic soils was studied in a 50-day laboratory experiment. The application of crop residues into the soil increased the N2O emission from the soil. The N2O emission was lower from the poorly managed soil as compared to the soil with the high degree of cultivation. The crop residues form the following decreasing sequence in terms of their effect on the cumulative N2O flow: cabbage > red clover > perennial grasses > straw of spring wheat. The composting of crop residues with a wide C: N ratio for 50 days did not exceed the critical value of the emission factor (1.25%), whereas, in the composting of crop residues with a narrow C: N ratio, the critical value of the emission factor was 1.3–2.0 times higher.  相似文献   

18.
Summary The hypotheses that disruption of soil structure increases mineralization rates in loams and clays more than in sandy soils and that this increase can be used to estimate the fraction of physically protected organic matter were tested. C and N mineralization was measured in undisturbed, and in finely and coarsely sieved moist or dried/remoistened soil. Fine sieving caused a temporary increase in mineralization. The relative increase in mineralization was much larger in loams and clays than in sandy soils and much larger for N than for C. The combination of remoistening and sieving of the soil gave a further increase in the mineralization flush after the disturbance. Again, the extra flush was larger in loams and clays than in sandy soils, and larger for N than for C. In loams and clays, small pores constituted a higher percentage of the total pore space than in sandy soils. The fraction of small pores explained more than 50% of the variation in the N mineralization rate between soils. There was also a good correlation between the small-pore fraction and the relative increase in N mineralization with fine sieving. For C, these relations were not clear. It is suggested that a large part of the organic matter that was present in the small pores could not be reached by microorganisms, and was therefore physically protected against decomposition. Fine sieving exposed part of this fraction to decomposition. This physically protected organic matter had a lower C: N ratio than the rest of the soil organic matter. The increase in N mineralization after fine sieving can be regarded as a measure of physically protected organic matter.  相似文献   

19.

Purpose  

A large amount of nitrogen (N) fertilizers has been broadcasted over soil surface for reliable crop production. Unfortunately, the broadcasted N vulnerable to volatilization and leaching can lead to serious environmental problems. As a new approach to mitigate N loss of broadcasted fertilizers, massive intercalation of urea into montmorillonite (MMT) was recently proposed to innovatively enhance the urea use efficiency. This study focuses on demonstrating the behaviors of the urea intercalated into MMT in soils.  相似文献   

20.
Altered soil nutrient cycling under future climate scenarios may affect pasture production and fertilizer management. We conducted a controlled-environment study to test the hypothesis that long-term exposure of pasture to enriched carbon dioxide (CO2) would lower soil nutrient availability. Perennial ryegrass was grown for 9 weeks under ambient and enriched (ambient + 120 ppm) CO2 concentrations in soil collected from an 11.5-year free air CO2 enrichment experiment in a grazed pasture in New Zealand. Nitrogen (N) and phosphorus (P) fertilizers were applied in a full factorial design at rates of 0, 12.5, 25 or 50 kg N ha−1 and 0, 17.5 or 35 kg P ha−1. Compared to ambient CO2, under enriched CO2 without P fertilizer, total plant biomass did not respond to N fertilizer, and tissue N/P ratio was increased indicating that P was co-limiting. This limitation was alleviated with the lowest rate of P fertilizer (17.5 kg P ha−1). Plant biomass in both CO2 treatments increased with increasing N fertilizer when sufficient P was available. Greater inputs of P fertilizer may be required to prevent yield suppression under enriched CO2 and to stimulate any response to N.  相似文献   

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