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1.
Nitrous oxide (N2O) is a potent greenhouse gas and, in New Zealand, about one‐third of the total greenhouse gas emissions from the agricultural sector are of N2O, mostly derived from animal excreta in grazed pasture soils. The aim of this study was to determine the effectiveness of a nitrification inhibitor, dicyandiamide (DCD), in reducing N2O emissions from animal urine patches in four different soils located in different regions of New Zealand with different soil, climatic and management conditions. The four soils are Templeton fine sandy loam and Lismore stony silt loam in Canterbury in the South Island, Horotiu silt loam in the Waikato region and Taupo pumice sand near Lake Taupo, both in the North Island. Results showed that the application of a fine‐particle suspension nitrification inhibitor, DCD, to grazed pasture soils was very effective in reducing N2O emissions in all four different soils. Total N2O emissions (over 69–137 days) from animal urine patches ranged from 1 to 20.9 kg N2O‐N ha?1 without DCD. These were reduced to 0.31–5.7 kg N2O‐N ha?1 by the use of DCD, representing 61–73% reductions (with an average of 70% reduction). The N2O‐N emission factor from animal urine N, EF3, was reduced from an average of 0.9 to 0.3% by the use of DCD. These results demonstrate the potential of using nitrification inhibitors to mitigate N2O emissions in a wide range of grazed pasture soils under different climatic and management conditions.  相似文献   

2.
Abstract. In grazed dairy pasture systems, a major source of NO3– leached and N2O emitted is the N returned in the urine from the grazing animal. The objective of this study was to use lysimeters to measure directly the effectiveness of a nitrification inhibitor, dicyandiamide (DCD), in decreasing NO3– leaching and N2O emissions from urine patches in a grazed dairy pasture under irrigation. The soil was a free‐draining Lismore stony silt loam (Udic Haplustept loamy skeletal) and the pasture was a mixture of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens). The use of DCD decreased NO3–‐N leaching by 76% for the urine N applied in the autumn, and by 42% for urine N applied in the spring, giving an annual average reduction of 59%. This would reduce the NO3–‐N leaching loss in a grazed paddock from 118 to 46 kg N ha–1 yr–1. The NO3–‐N concentration in the drainage water would be reduced accordingly from 19.7 to 7.7 mg N L–1, with the latter being below the drinking water guideline of 11.3 mg N L–1. Total N2O emissions following two urine applications were reduced from 46 kg N2O‐N ha–1 without DCD to 8.5 kg N2O‐N with DCD, representing an 82% reduction. In addition to the environmental benefits, the use of DCD also increased herbage production by more than 30%, from 11 to 15 t ha–1 yr–1. The use of DCD therefore has the potential to make dairy farming more environmentally sustainable by reducing NO3– leaching and N2O emissions.  相似文献   

3.

Purpose  

Methanotrophs are an important group of methane (CH4)-oxidizing bacteria in the soil, which act as a major sink for the greenhouse gas, CH4. In grazed grassland, one of the ecologically most sensitive areas is the animal urine patch soil, which is a major source of both nitrate (NO3 −) leaching and nitrous oxide (N2O) emissions. Nitrification inhibitors, such as dicyandiamide (DCD), have been used to mitigate NO3 − leaching and N2O emissions in grazed pastures. However, it is not clear if the high nitrogen loading rate in the animal urine patch soil and the use of nitrification inhibitors would have an impact on the abundance of methanotrophs in grazed grassland soils. The purpose of this study was to determine the effect of animal urine and DCD on methanotroph abundance in grazed grassland soils.  相似文献   

4.
 N2O emissions from a transplanted irrigated rice grown on a Typic Ustochrept soil at New Delhi, India, were studied to evaluate the effect of N fertilizers, i.e. urea and (NH4)2SO4, alone and in combination with the nitrification inhibitors dicyandiamide (DCD) and thiosulphate. The addition of urea and (NH4)2SO4 increased N2O emissions considerably when compared to no fertilizer N application (control). N2O measurement in the field was done by a closed-chamber method for a period of 98 days. The application of urea with DCD and thiosulphate reduced N2O fluxes considerably. The highest total N2O-N emission (235 g N2O-N ha–1) was from the (NH4)2SO4 treatment, which was significantly higher than the total N2O-N emission from the urea treatment (160 g N2O-N ha–1). DCD reduced N2O-N emissions by 11% and 26% when applied with urea and(NH4)2SO4, respectively, whereas thiosulphate in combination with urea reduced N2O-N emissions by 9%. Total N2O-N emissions were found to range from 0.08% to 0.14% of applied N. N2O emissions were low during submergence and increased substantially during drainage of standing water. Received: 20 October 1999  相似文献   

5.
Fluxes of N2O were studied in a Norway spruce forest in the southwest of Sweden. Three differently treated catchments were compared: Limed (6 t dolomite ha–1), Nitrex (additional N-deposition corresponding to 35 kg ha–1 year–1, in small doses) and Control (used as control site). The N-retention was still high (95%) after 2years of N-addition at the Nitrex site when the flux measurements were performed. Each catchment contained both well-drained and poorly drained soils (covered with Sphagnum sp.). The emissions of N2O were in general low with both a high spatial and temporal variation for all three sites. The measured emissions were 25, 71 and 96 (gN2O-N ha–1 year–1) for the well-drained Limed, Control and Nitrex sites, respectively. The average emissions of N2O from the wet areas were significantly higher than the well-drained areas within the catchments. For the wet areas the measured emissions were larger: 90, 118 and 254 (g N2O-N ha–1 year–1) for the Limed, Control and Nitrex sites, respectively. Comparison between treatments showed the wet Nitrex site to have a significantly higher emission than all other sites. The increased N-deposition at the Nitrex site increased the N2O emissions by 0.2% of the added N for the well-drained soils and about 1% for the wet areas, compared with the control site. Since the wet areas represented only a small part of the forest, their larger emissions did not contribute significantly to the overall emission of the forest. Neither temperature nor water content of the soil was well correlated with the N2O emissions. Soil gas samples showed that most of the N2O was produced below a 0.3-m depth in the soil. Received: 27 September 1996  相似文献   

6.
 Nitrous oxide (N2O) emissions and methane (CH4) consumption were quantified following cultivation of two contrasting 4-year-old pastures. A clover sward was ploughed (to 150–200 mm depth) while a mixed herb ley sward was either ploughed (to 150–200 mm depth) or rotovated (to 50 mm depth). Cumulative N2O emissions were significantly greater following ploughing of the clover sward, with 4.01 kg N2O-N ha–1 being emitted in a 48-day period. Emissions following ploughing and rotovating of the ley sward were much less and were not statistically different from each other, with 0.26 and 0.17 kg N2O-N ha–1 being measured, respectively, over a 55-day period. The large difference in cumulative N2O between the clover and ley sites is presumably due to the initially higher soil NO3 – content, greater water filled pore space and lower soil pH at the clover site. Results from a denitrification enzyme assay conducted on soils from both sites showed a strong negative relationship (r=–0.82) between soil pH and the N2O:(N2O+N2) ratio. It is suggested that further research is required to determine if control of soil pH may provide a relatively cheap mitigation option for N2O emissions from these soils. There were no significant differences in CH4 oxidation rates due to sward type or form of cultivation. Received: 1 November 1998  相似文献   

7.
Nitrous oxide emission (N2O) from applied fertilizer across the different agricultural landscapes especially those of rainfed area is extremely variable (both spatially and temporally), thus posing the greatest challenge to researchers, modelers, and policy makers to accurately predict N2O emissions. Nitrous oxide emissions from a rainfed, maize-planted, black soil (Udic Mollisols) were monitored in the Harbin State Key Agroecological Experimental Station (Harbin, Heilongjiang Province, China). The four treatments were: a bare soil amended with no N (C0) or with 225?kg?N ha?1 (CN), and maize (Zea mays L.)-planted soils fertilized with no N (P0) or with 225?kg?N ha?1 (PN). Nitrous oxide emissions significantly (P?<?0.05) increased from 141?±?5?g N2O-N?ha?1 (C0) to 570?±?33?g N2O-N?ha?1 (CN) in unplanted soil, and from 209?±?29?g N2O-N?ha?1 (P0) to 884?±?45?g N2O-N?ha?1 (PN) in planted soil. Approximately 75?% of N2O emissions were from fertilizer N applied and the emission factor (EF) of applied fertilizer N as N2O in unplanted and planted soils was 0.19 and 0.30?%, respectively. The presence of maize crop significantly (P?<?0.05) increased the N2O emission by 55?% in the N-fertilized soil but not in the N-unfertilized soil. There was a significant (P?<?0.05) interaction effect of fertilization?×?maize on N2O emissions. Nitrous oxide fluxes were significantly affected by soil moisture and soil temperature (P?<?0.05), with the temperature sensitivity of 1.73–2.24, which together explained 62–76?% of seasonal variation in N2O fluxes. Our results demonstrated that N2O emissions from rainfed arable black soils in Northeast China primarily depended on the application of fertilizer N; however, the EF of fertilizer N as N2O was low, probably due to low precipitation and soil moisture.  相似文献   

8.
Nitrogen (N) losses via nitrate (NO3−) leaching, ammonia (NH3) volatilization and nitrous oxide (N2O) emissions from grazed pastures in New Zealand are one of the major contributors to environmental degradation. The use of N inhibitors (urease and nitrification inhibitors) may have a role in mitigating these N losses. A one-year field experiment was conducted on a permanent dairy-grazed pasture site at Massey University, Palmerston North, New Zealand to quantify these N losses and to assess the effect of N inhibitors in reducing such losses during May 2005-2006. Cow urine at 600 kg N ha−1 rate with or without urease inhibitor N-(n-butyl) thiophosphoric triamide (nBTPT) or (trade name “Agrotain”) (3 L ha−1), nitrification inhibitor dicyandiamide (DCD) (7 kg ha−1) and the use of double inhibitor (DI) containing a combination of both Agrotain and DCD (3:7) were applied to field plots in autumn, spring and summer. Pasture production, NH3 and N2O fluxes, soil mineral N concentrations, microbial biomass C and N, and soil pH were measured following the application of treatments during each season. All measured parameters, except soil microbial biomass C and N, were influenced by the added inhibitors during the three seasons. Agrotain reduced NH3 emissions over urine alone by 29%, 93% and 31% in autumn, spring and summer respectively but had little effect on N2O emission. DCD reduced N2O emission over urine alone by 52%, 39% and 16% in autumn, spring and summer respectively but increased NH3 emission by 56%, 9% and 17% over urine alone during those three seasons. The double inhibitor reduced NH3 by 14%, 78% and 9% and N2O emissions by 37%, 67% and 28% over urine alone in autumn, spring and summer respectively. The double inhibitor also increased pasture dry matter by 10%, 11% and 8% and N uptake by the 17%, 28% and 10% over urine alone during autumn, spring and summer respectively. Changes in soil mineral N and pH suggested a delay in urine-N hydrolysis with Agrotain, and reduced nitrification with DCD. The combination of Agrotain and DCD was more effective in reducing both NH3 and N2O emissions, improving pasture production, controlling urea hydrolysis and retaining N in NH4+ form. These results suggest that the combination of both urease and nitrification inhibitors may have the most potential to reduce N losses if losses are associated with urine and improve pasture production in intensively grazed systems.  相似文献   

9.
Nitrous oxide (N2O) is a potent greenhouse gas, and nitrate () is a water contaminant. In grazed grassland, the major source of both leaching and N2O emissions is nitrogen (N) deposited in animal excreta, particularly in the urine. The objective of this study was to determine the effectiveness of two nitrification inhibitors: (i) a solution of dicyandiamide (DCD) and (ii) a liquid formulation of 3,4‐dimethylpyrazole phosphate (DMPP) for reducing N2O emissions and leaching from urine patch areas in two grazed pasture soils under different environmental conditions. In the Canterbury Templeton soil, the nitrification rate of ammonium from the animal urine applied at 1000 kg N/ha was significantly decreased by the application of DCD (10 kg/ha) and DMPP (5 kg/ha). N2O emissions, measured over a 3‐month period, from dairy cow urine applied to the Canterbury Templeton soil were 1.14 kg N2O‐N/ha, and this was reduced to 0.43 and 0.39 kg N2O‐N/ha by DCD and the liquid DMPP, respectively. These are equivalent to 62–66% reductions in the total N2O emissions. Nitrate leaching losses from dairy cow urine applied to the Waikato Horotiu soil lysimeters were reduced from 628.6 kg ‐N/ha to 400.6 and 451.5 kg ‐N/ha by the application of DCD (10 kg/ha) or DMPP (1 kg/ha), respectively. There was no significant difference between the DCD solution and the liquid DMPP in terms of their effectiveness in reducing N2O emissions or leaching under the experimental conditions of this study. These results suggest that both the liquid formulations of DCD and DMPP have the potential to be used as nitrification inhibitors to reduce N2O emissions and leaching in grazed pasture soils.  相似文献   

10.
Recent lysimeter studies have demonstrated that the nitrification inhibitor, dicyandiamide (DCD), can reduce nitrate (NO) leaching losses from cow urine patches in grazed pasture systems. The objective of this study was to quantify the effects of fine particle suspension (FPS) DCD on soil mineral N components, pasture yield, nutrient uptake and pasture quality under grazed pasture conditions. A field study was conducted on the Lincoln University dairy farm, Canterbury, New Zealand, from 2002 to 2006. FPS DCD was applied to grazed pasture plots at 10 kg ha?1 in early May in addition to applied cow urine patches at a nitrogen (N) loading rate of 1000 kg N ha?1, with DCD reapplied in early August. Soil mineral N levels in the urine patches were monitored. Pasture yield, N and cation concentrations and uptake were measured in treatment urine patches and inter‐urine areas of the pasture. Comparisons were made with control plots which did not receive DCD. NO levels under the DCD‐treated urine patches (0–7.5 cm) were in the order of 10 kg N ha?1 compared with 40–80 kg N ha?1 under untreated patches, and soil ammonium (NH) levels were consistently higher under the DCD‐treated patches. The DCD significantly and consistently increased pasture yield in both the urine patches, and inter‐urine areas of the pasture in all 4 years of the trial. Mean annual dry matter (DM) yields over 4 years were inter‐urine areas, 10.3; inter‐urine + DCD, 12.4; urine, 12.4 and urine +DCD 16.0 t DM ha?1, representing an average DM yield increase of 20 and 29% in inter‐urine and urine patch areas, respectively. On a whole paddock basis, the increase in annual DM yield resulting from DCD application was estimated to be 21%. N, calcium (Ca), magnesium (Mg) and potassium (K) concentrations in pasture were unaffected by treatment with DCD; however, total annual uptake of these nutrients by pasture was significantly higher in all years where DCD had been applied. Pasture DM, protein, carbohydrate, metabolizable energy and fibre levels and sward clover content were not affected by treatment with DCD. The results demonstrate the agronomic value of the DCD treatment in addition to the environmental benefits in a grazed pasture system.  相似文献   

11.
Abstract. Nitrous oxide (N2O) from animal excreta in grazed pasture systems makes up a significant component (c. 10%) of New Zealand's total greenhouse gas inventory. We report an effective method to decrease N2O emissions from animal urine patches by treating the soil with the nitrification inhibitor dicyandiamide (DCD), in a simulated grazed dairy pasture system under spray irrigation. The soil was a free-draining Lismore stony silt loam (Udic Haplustept loamy skeletal) and the pasture was a mixture of perennial ryegrass ( Lolium perenne ) and white clover ( Trifolium repens ). By treating the soil with DCD, N2O emissions were decreased by 76% following urine application in the autumn, from 26.7 kg N2O-N ha−1 without DCD to an average of 6.4 kg N2O-N ha−1 with DCD over the 6-month experimental period. N2O flux was decreased by 78% following urine application in the spring, from 18 kg N2O-N ha−1 without DCD to 3.9 kg N2O-N ha−1 with the application of DCD over the 3-month period. A single application of DCD immediately after urine was sufficient to effectively mitigate N2O emissions from the urine. The results showed that repeated applications of DCD after urine application, or mixing DCD with urine, offered no advantage over a single application of DCD immediately after urine deposition.  相似文献   

12.
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   

13.

Purpose

Dicyandiamide (DCD) has been used commercially in New Zealand to reduce nitrate leaching and N2O emissions in grazed pastures. However, there is a lack of information in the literature on the optimum rate of DCD to achieve the environmental benefits while at the same time reducing the cost of the technology. The objective of this study was to determine the effect of DCD application rate on its effectiveness to inhibit ammonia oxidizer growth and nitrification rate in a grazed pasture soil.

Materials and methods

The soil was a Templeton silt loam (Immature Pallic Soil; Udic Haplustepts) collected from Lincoln University Research Dairy Farm with a mixed pasture consisting of perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) and was incubated alone (control) or with cow urine at 700 kg N/ha with 6 rates of DCD [0, 2.5, 5, 7.5, 10 (applied twice), 15 and 20 kg/ha] in incubation vessels. The incubation vessels were placed randomly in an incubator with a constant temperature of 12 °C. During 112 days of incubation, soil subsamples were taken at different time intervals to measure the concentrations of NO3 ?-N and NH4 +-N and the amoA gene copy numbers of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA).

Results and discussion

DCD applied at all the different rates inhibited nitrification in urine-treated soils, but the effectiveness increased with DCD application rate. In addition, AOB growth and the amounts of nitrate-N in the soil were significantly related to the application rate of DCD. However, AOA population abundance showed no relationship to the application rate of DCD. The DCD rate at which the AOB growth rate and nitrate-N concentration were halved (effective dosage that causes 50 % reduction in nitrification rate, or ED50) was about 10 kg DCD/ha.

Conclusions

These results suggest that DCD applied at relatively low rates still slowed down the nitrification rate, and the current recommended rate of 10 kg DCD/ha for DCD use in New Zealand grazed pastures would result in a 50 % reduction in nitrification rate in this soil. The actual rate of DCD application used would depend on the cost of the product and the environmental and agronomic benefits that would result from its use.  相似文献   

14.

Purpose  

Nitrous oxide emissions from pasture soils account for one third of total agricultural greenhouse gas emissions in New Zealand. The aim of this study was to determine nitrous oxide (N2O) emissions from animal urine patches under summer (with irrigation) and winter conditions as affected by dicyandiamide (DCD) in grazed grassland in New Zealand.  相似文献   

15.
 In this study an inventory of N2O emissions from agriculture in Belgium was made according to the Intergovernmental Panel on Climate Change (IPCC) guidelines. Three sources of N2O were distinguished between: (1) direct N2O emissions from agricultural soils (N2O-direct), (2) N2O emissions due to animal production systems (N2O-animals), and (3) indirect N2O emissions as a result of N losses from agricultural soils (N2O-indirect). In 1996, the total N2O emission from agriculture in Belgium was 12.8×106 kg N2O-N. N2O-direct, N2O-animals and N2O-indirect contributed 60%, 7% and 33%, respectively, to the total N2O emission. The IPCC methodology tended to give an overestimate of the N2O emission from agriculture by 45% when IPCC default values were used instead of country-specific N-input data. Between 1950 and 1996, the total N2O emission from agriculture in Belgium increased from 8.4×106 kg N2O-N to 12.8×106 kg N2O-N. This was an increase of 53%, or about 0.1×106 kg N2O-N-year–1. Received: 25 May 1999  相似文献   

16.
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   

17.
 Nitrous oxide (N2O) emissions were measured from an irrigated sandy-clay loam cropped to maize and wheat, each receiving urea at 100 kg N ha–1. During the maize season (24 August–26 October), N2O emissions ranged between –0.94 and 1.53 g N ha–1 h–1 with peaks during different irrigation cycles (four) ranging between 0.08 and 1.53 g N ha–1 h–1. N2O sink activity during the maize season was recorded on 10 of the 29 sampling occasions and ranged between 0.18 and 0.94 g N ha–1 h–1. N2O emissions during the wheat season (22 November–20 April) varied between –0.85 and 3.27 g N ha–1 h–1, whereas peaks during different irrigation cycles (six) were in the range of 0.05–3.27 g N ha–1 h–1. N2O sink activity was recorded on 14 of the 41 samplings during the wheat season and ranged between 0.01 and 0.87 g N ha–1 h–1. Total N2O emissions were 0.16 and 0.49 kg N ha–1, whereas the total N2O sink activity was 0.04 and 0.06 kg N ha–1 during the maize and wheat seasons, respectively. N2O emissions under maize were significantly correlated with denitrification rate and soil NO3 –-N but not with soil NH4 +-N or soil temperature. Under wheat, however, N2O emissions showed a strong correlation with soil NH4 +-N, soil NO3 –-N and soil temperature but not with the denitrification rate. Under either crop, N2O emissions did not show a significant relationship with water-filled pore space or soil respiration. Received: 11 June 1997  相似文献   

18.
Nitrogen dynamics in different types of pasture in the Austrian Alps   总被引：7，自引：0，他引：7  
 Soil N dynamics were compared in Alpine pastures on two mountains. N-pool sizes and N fluxes were measured relative to N losses via leaching and denitrification in summer. On each mountain, four types of pasture were studied: (1) forest pastures, (2) recently developed pastures formed by forest clearance ("new pastures"), (3) older established pastures, and (4) pastures planted with clover. At both study sites (Scheuchegg and Teufelstein) we obtained similar results. Compared with forest pasture soils, open pasture soils were found to have greater microbial biomass and faster mineralisation potentials, but net field mineralisation rates were slower. In the forest pastures, highest N losses via denitrification were found. Higher potential leaching of NO3 –, estimated by accumulation of NO3 – on ion-exchange resins, in the forest pasture soils suggests lower N uptake by microbes and herbaceous plants compared with open pastures. N2O-production rates of the forest pasture soils at the Scheuchegg site (11.54 μg N2O-N m–2 h–1) were of similar magnitude to those reported for spruce forests without pastures, but at Teufelstein (53.75 μg N2O-N m–2 h–1) they were higher. However, if forest pastures are not overgrazed, no elevated N loss through N2O production and leaching of NO3 – is expected. Denitrification rates in the open pastures (0.83–7.50 μg N2O-N m–2 h–1) were low compared with reports on lowland pastures. In soils of the new pastures, rates of microbial N processes were similar to those in the established pastures, indicating a high capacity of soils to restore their internal N cycle after forest clearance. Received: 19 August 1999  相似文献   

19.
Tools to manage the emission of the greenhouse gas nitrous oxide (N2O), an intermediate of both nitrification and denitrification, from soils are limited. To date, the nitrification inhibitor dicyandiamide (DCD) is one of the most effective tools available to livestock farmers for reducing N2O emissions and minimizing leaching of nitrogen in response to increased urine deposition in grazed pasture systems. Despite its effectiveness in decreasing N losses from animal urine by inhibiting N processes in soils, the effect of DCD on the population structure of denitrifiers and overall bacterial community composition is still uncertain. Here we use three New Zealand dairy-grazed pasture soils to determine the effects of DCD application on microbial community richness and composition at both functional (genes involved in the denitrification process) and phylogenetic (overall bacterial community composition based on 16S rRNA profiling) levels. Results further confirm that the effects on microbial populations are minimal and transient in nature. The impact of DCD on microbial community structure was soil dependent, and a greater effect was attributed to intrinsic soil properties like soil texture, with community response to DCD in combination with urine being comparable to that under urine alone. Addition of DCD to cattle urine also reduced N2O emission between 23 and 67%.  相似文献   

20.

Purpose

Climate change is arguably the biggest environmental challenge facing humanity today. Livestock production systems are a major source of greenhouse gases that contribute to climate change. Nitrous oxide (N2O) is a potent greenhouse gas with a long-term global warming potential 298 times that of carbon dioxide (CO2). Nitrate (NO3 ?) leaching from soil causes water contamination, and this is a major environmental issue worldwide. Agriculture is identified as the dominant source for NO3 ? in surface and ground waters. In grazed grassland systems where animals graze outdoor pastures, most of the N2O and NO3 ? are from nitrogen (N) returned to the soil in the excreta of the grazing animal, particularly the urine. This paper reviews published literature on the use of nitrification inhibitors (NI) to treat grazed pasture soils to mitigate NO3 ? leaching and N2O emissions.

Materials and methods

This paper provides a review on: ammonia oxidisers, including ammonia oxidising bacteria (AOB) and ammonia oxidising archaea (AOA), that are responsible for ammonia oxidation in the urine patch areas of grazed pastures; the effectiveness of NIs, such as dicyandiamide (DCD) and 3,4-dimethylpyrazole phosphate (DMPP), in inhibiting the growth and activity of ammonia oxidisers; the efficacy of DCD and DMPP in reducing NO3 ? leaching and N2O emissions in grazed pastures; additional benefits of using NI in grazed pasture, including increased pasture production, decreased cation leaching and decreased NO3 ? concentrations in plants; and major factors that may affect the efficacy of NIs.

Results and discussion

Research from a number of laboratory and field studies have conclusively demonstrated that treating grazed pasture soils with a NI, such as DCD, is an effective means of reducing NO3 ? leaching and N2O emissions from grazed livestock production systems. Results show that N2O emissions from animal urine-N can be reduced by an average of 57 % and NO3 ? leaching from animal urine patches can be reduced by 30 to 50 %. The NI technology has been shown to be effective under a wide range of soil and environmental conditions. The NI technology also provides other benefits, including increased pasture production, reduced cation (Ca2+, Mg2+ and K+) leaching and reduced NO3 ? concentration in pasture plants which would reduce the risk of NO3 ? poisoning for the animal.

Conclusions

The use of NIs such as DCD to treat grazed pasture soil is a scientifically sound and practically viable technology that can effectively mitigate NO3 ? leaching and N2O emissions in grazed livestock production systems.
  相似文献   

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