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1.
Denitrification rates are often greater in no-till than in tilled soils and net soil-surface greenhouse gas emissions could be increased by enhanced soil N 2O emissions following adoption of no-till. The objective of this study was to summarize published experimental results to assess whether the response of soil N 2O fluxes to the adoption of no-till is influenced by soil aeration. A total of 25 field studies presenting direct comparisons between conventional tillage and no-till (approximately 45 site-years of data) were reviewed and grouped according to soil aeration status estimated using drainage class and precipitation during the growing season. The summary showed that no-till generally increased N 2O emissions in poorly-aerated soils but was neutral in soils with good and medium aeration. On average, soil N 2O emissions under no-till were 0.06 kg N ha −1 lower, 0.12 kg N ha −1 higher and 2.00 kg N ha −1 higher than under tilled soils with good, medium and poor aeration, respectively. Our results therefore suggest that the impact of no-till on N 2O emissions is small in well-aerated soils but most often positive in soils where aeration is reduced by conditions or properties restricting drainage. Considering typical soil C gains following adoption of no-till, we conclude that increased N 2O losses may result in a negative greenhouse gas balance for many poorly-drained fine-textured agricultural soils under no-till located in regions with a humid climate. 相似文献
2.
Nitrous oxide (N 2O) is a greenhouse gas and agricultural soils are major sources of atmospheric N 2O. Its emissions from soils make up the largest part in the global N 2O budget. Research was carried out at the experimental fields of the Leibniz-Institute of Agricultural Engineering Potsdam-Bornim (ATB). Different types (mineral and wood ash) and levels (0, 75 and 150 kg N ha −1) of fertilization were applied to annual (rape, rye, triticale and hemp) and perennial (poplar and willow) plants every year. N 2O flux measurements were performed 4 times a week by means of gas flux chambers and an automated gas chromatograph between 2003 and 2005. Soil samples were also taken close to the corresponding measuring rings. Soil nitrate and ammonium were measured in soil extracts.N 2O emissions had a peak after N fertilization in spring, after plant harvest in summer and during the freezing–thawing periods in winter. Both fertilization and plant types significantly altered N 2O emission. The maximum N 2O emission rate detected was 1081 μg N 2O m −2 h −1 in 2004. The mean annual N 2O emissions from the annual plants were more than twofold greater than those of perennial plants (4.3 kg ha −1 vs. 1.9 kg ha −1). During January, N 2O fluxes considerably increased in all treatments due to freezing–thawing cycles. Fertilization together with annual cropping doubled the N 2O emissions compared to perennial crops indicating that N use efficiency was greater for perennial plants. Fertilizer-derived N 2O fluxes constituted about 32% (willow) to 67% (rape/rye) of total soil N 2O flux. Concurrent measurements of soil water content, NO 3 and NH 4 support the conclusion that nitrification is main source of N 2O loss from the study soils. The mean soil NO 3-N values of soils during the study for fertilized soils were 1.6 and 0.9 mg NO 3-N kg −1 for 150 and 75 kg N ha −1 fertilization, respectively. This value reduced to 0.5 mg NO 3-N kg −1 for non-fertilized soils. 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 (CO 2), nitrous oxide (N 2O) and methane (CH 4) 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 N 2O 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 CO 2 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.
Field operations of tillage and residue incorporation could have potentially important influences on N-trace gas fluxes, though poorly quantified. Here we studied the effects of straw incorporation in the preceding rice season and no-tillage prior to wheat sowing on nitric oxide (NO) and nitrous oxide (N 2O) emissions during the non-rice period of a typical rice-wheat rotation in the Yangtze River Delta. Compared to conventional management practice (no straw incorporation along with rotary harrowing tillage to 10 cm before wheat sowing), straw incorporation alone decreased cumulative N 2O emissions over the entire non-rice period by 32% (1.53 vs. 2.24 kg N ha -1, P < 0.05) but did not affect NO emissions (0.88 vs. 0.87 kg N ha −1). In contrast, no-tillage alone increased N 2O emissions by 75% ( P < 0.05) while reducing NO emissions by 48% ( P < 0.01). Combination of no-tillage and straw incorporation led to no change in N 2O emissions but a reduction in NO emissions compared to the conventional management regime. The direct N 2O emission factors (EF ds) of applied nitrogen fertilizers during the non-rice season ranged from 0.29% to 1.35% with a coefficient of variation (CV) as large as 68% among the investigated management regimes. The EF ds for NO ranged from 0.13% to 0.32% with a CV of 50%. Adoption of these new EF ds will allow us to account for management effects on N-trace gas emissions when calculating emission inventories. Nevertheless, it is noteworthy that the uncertainty remains high, since the effects of soil properties such as texture or pH on management practices are not yet well defined. 相似文献
5.
Nitrogen amendment followed by flooding irrigation is a general management practice for a wheat–maize rotation in the North China Plain, which may favor nitrification and denitrification. Consequently, high emissions of nitrous oxide (N 2O) and nitric oxide (NO) are hypothesized to occur. To test this hypothesis, we performed year-round field measurements of N 2O and NO fluxes from irrigated wheat–maize fields on a calcareous soil applied with all crop residues using a static, opaque chamber measuring system. To interpret the field data, laboratory experiments using intact soil cores with added carbon (glucose) and nitrogen (nitrate, ammonium) substrates were performed. Our field measurements showed that pulse emissions after fertilization and irrigation/rainfall contributed to 73% and 88% of the annual N 2O and NO emissions, respectively. Soil moisture and mineral nitrogen contents significantly affected the emissions of both gases. Annual emissions from fields fertilized at the conventional rate (600 kg N ha −1 yr −1) totaled 4.0 ± 0.2 and 3.0 ± 0.2 kg N ha −1 yr −1 for N 2O and NO, respectively, while those from unfertilized fields were much lower (0.5 ± 0.02 kg N ha −1 yr −1 and 0.4 ± 0.05 kg N ha −1 yr −1, respectively). Direct emission factors (EF ds) of N 2O and NO for the fertilizer nitrogen were estimated to be 0.59 ± 0.04% and 0.44 ± 0.04%, respectively. By summarizing the results of our study and others, we recommended specific EF ds (N 2O: 0.54 ± 0.09%; NO: 0.45 ± 0.04%) for estimating emissions from irrigated croplands on calcareous soils with organic carbon ranging from 5 to 16 g kg −1. Nitrification dominated the processes driving the emissions of both gases following fertilization. It was evident that insufficient available carbon limited microbial denitrification and thus N 2O emission. This implicates that efforts to enhance carbon sink in calcareous soils likely increase their N 2O emissions. 相似文献
6.
PurposeThe aim of this research was to quantify the effect of plantain (Plantago lanceolata L.) on soil nitrification rate, functional gene abundance of soil ammonia oxidisers, and the concomitant effect on nitrous oxide emissions from urine patches in a shallow, free-draining soil in Canterbury during late autumn/winter season. Materials and methodsUrine was collected from dairy cows grazing either ryegrass/white clover (RGWC), 30% plantain (P30) mixed in with RGWC or 100% plantain (P100) pasture, and applied at two rates (700 or 450 kg N ha?1) to intact soil blocks growing either RGWC, P30 or P100 pasture. Results and discussionResults showed that increased plantain content reduced N-concentration in urine from 7.2 in RGWC urine to 4.5 and 3.7 g N L?1 in P30 and P100 urine, respectively. Total N2O emissions and emission factors (EF3) from urine-treated pastures were low, <?2 kg N ha?1 and <?0.22%, respectively. Urine application at the lower urine N-loading rate of 450 kg N ha?1 (i.e. representative of that in a P30 urine patch) resulted in 30% lower N2O emissions (P?<?0.01) and 35% lower soil nitrate concentrations (P?<?0.001) compared to those at the higher urine loading rate of 700 kg N ha?1 (i.e. representative of that in a RGWC urine patch). Increasing plantain content in the pasture sward from 0 to 30% and 100% with urine N applied at the same loading rate did not reduce N2O emissions or nitrification compared to the standard ryegrass-white clover pasture. Cow urine derived from the different pasture diets had no effect on N2O emissions, N transformation or ammonia-oxidiser abundance in soil compared to the RGWC urine applied at the same rate. ConclusionsThe main effect of plantain in this study appears to be related to the reduction in urine N-loading rate, rather than factors related to urine properties or plantain-soil interactions. 相似文献
7.
This study provides a comparative assessment of greenhouse gas (GHG) emissions when converting a reclaimed minesoil that was previously under meadow to miscanthus ( Miscanthus × giganteus ) and maize ( Zea mays L.) land uses in Ohio, USA. Additionally, effluent from an anaerobic digester at rates of 0, 75, 150, and 225 kg N ha −1 rates was also assessed for C and nutrient fertilization. Results from the study show that land use conversion to maize had the highest net release of GHG equivalent of 6·6 Mg CO 2equ ha −1 y −1, on average, across effluent application rates. Under miscanthus land use with no and high effluent application rates, net GHG equivalent on average was 4·3 Mg CO 2equ ha −1 y −1, which was larger when compared with that under the meadow land use (1·6 Mg CO 2equ ha −1 y −1). Miscanthus land use under medium rates of effluent application had similar net GHG equivalent (7·1 Mg CO 2equ ha −1 y −1) to the maize land use. The application of effluent did increase CO 2–C and N 2O–N emissions; but increases in above‐ground–below‐ground biomass production (1·6 Mg C ha −1) in the meadow land use and C input from effluent retained in the soil in the miscanthus and maize land uses offset most of the effluent‐induced GHG equivalent emissions. Contribution of cumulative N 2O–N to GHG equivalent emissions in general was 11% when no effluent was applied and 22% when effluent was applied across land uses. Findings from this study show that land use changes from antecedent meadow to maize and miscanthus during the first year of establishment would result in net increase of GHG emissions. Published 2017. This article is a U.S. Government work and is in the public domain in the USA 相似文献
8.
Nitrous oxide (N 2O) and methane (CH 4) emitted by anthropogenic activities have been linked to the observed and predicted climate change. Conservation tillage practices such as no-tillage (NT) have potential to increase C sequestration in agricultural soils but patterns of N 2O and CH 4 emissions associated with NT practices are variable. Thus, the objective of this study was to evaluate the effects of tillage practices on N 2O and CH 4 emissions in long-term continuous corn ( Zea mays) plots. The study was conducted on continuous corn experimental plots established in 1962 on a Crosby silt loam (fine, mixed, mesic Aeric Ochraqualf) in Ohio. The experimental design consisted of NT, chisel till (CT) and moldboard plow till (MT) treatments arranged in a randomized block design with four replications. The N 2O and CH 4 fluxes were measured for 1-year at 2-week intervals during growing season and at 4-week intervals during the off season. Long-term NT practice significantly decreased soil bulk density ( ρb) and increased total N concentration of the 0–15 cm layer compared to MT and CT. Generally, NT treatment contained higher soil moisture contents and lower soil temperatures in the surface soil than CT and MT during summer, spring and autumn. Average daily fluxes and annual N 2O emissions were more in MT (0.67 mg m −2 d −1 and 1.82 kg N ha −1 year −1) and CT (0.74 mg m −2 d −1 and 1.96 kg N ha −1 year −1) than NT (0.29 mg m −2 d −1 and 0.94 kg N ha −1 year −1). On average, NT was a sink for CH 4, oxidizing 0.32 kg CH 4-C ha −1 year −1, while MT and CT were sources of CH 4 emitting 2.76 and 2.27 kg CH 4-C ha −1 year −1, respectively. Lower N 2O emission and increased CH 4 oxidation in the NT practice are attributed to decrease in surface ρb, suggesting increased gaseous exchange. The N 2O flux was strongly correlated with precipitation, air and soil temperatures, but not with gravimetric moisture content. Data from this study suggested that adoption of long-term NT under continuous corn cropping system in the U.S. Corn Belt region may reduce GWP associated with N 2O and CH 4 emissions by approximately 50% compared to MT and CT management. 相似文献
9.
Quantifying the nitrous oxide (N 2O) and nitric oxide (NO) fluxes emitted from croplands remains a major challenge. Field measurements in different climates, soil and agricultural conditions are still scarce and emissions are generally assessed from a small number of measurements. In this study, we report continuously measured N 2O and NO fluxes with a high temporal resolution over a 2-year crop sequence of barley and maize in northern France. Measurements were carried out using 6 automatic chambers at a rate of 16 mean flux measurements per day. Additional laboratory measurements on soil cores were conducted to study the response of NO and N 2O emissions to environmental conditions.The detection limit of the chamber setup was found to be 3 ng N m −2 s −1 for N 2O and 0.1 ng N m −2 s −1 for NO. Nitrous oxide fluxes were higher than the threshold 37% of the time, while they were 72% of the time for NO fluxes.The cumulated annual NO and N 2O emissions were 1.7 kg N 2O-N ha −1 and 0.5 kg NO-N ha −1 in 2007, but 2.9 kg N 2O-N ha −1 and 0.7 kg NO-N ha −1 in 2008. These inter-annual differences were largely related to crop types and to their respective management practices. The forms, amounts and timing of nitrogen applications and the mineralization of organic matter by incorporation of crop residues were found to be the main factor controlling the emissions peaks. The inter-annual variability was also due to different weather conditions encountered in 2007 and 2008. In 2007, the fractioned N inputs applied on barley (54 kg ha −1 in March and in April) did not generate N 2O emissions peaks because of the low rainfall during the spring. However, the significant rainfall observed in the summer and fall of 2007, promoted rapid decomposition of barley residues which caused high levels of N 2O emissions. In 2008, the application of dairy cattle slurry and mineral fertilizer before the emergence of maize (107 kg N min ha −1 or 130 kg N tot ha −1 in all) coincided with large rainfalls promoting both NO and N 2O emissions, which remained high until early summer.Laboratory measurements corroborated the field observations: NO fluxes were maximum at a water-filled pore space (WFPS) of around 27% while N 2O fluxes were optimal at 68% WFPS, with a maximum potentially 14 times larger than for NO. 相似文献
10.
Conservation tillage practices are widely used to protect against soil erosion and soil C losses, whereas winter cover crops are used mainly to protect against N losses during autumn and winter. For the greenhouse gas balance of a cropping system the effect of reduced tillage and cover crops on N 2O emissions may be more important than the effect on soil C. This study monitored emissions of N 2O between September 2008 and May 2009 in three tillage treatments, i.e., conventional tillage (CT), reduced tillage (RT) and direct drilling (DD), all with (+CC) or without (−CC) fodder radish as a winter cover crop. Cover crop growth, soil mineral N dynamics, and other soil characteristics were recorded. Furthermore, soil concentrations of N 2O were determined eight times during the monitoring period using permanently installed needles. There was little evidence for effects of the cover crop on soil mineral N. Following spring tillage and slurry application soil mineral N was dominated by the input from slurry. Nitrous oxide emissions during autumn, winter and early spring remained low, although higher emissions from +CC treatments were indicated after freezing events. Following spring tillage and slurry application by direct injection N 2O emissions were stimulated in all tillage treatments, reaching 250-400 μg N m −2 h −1 except in the CT + CC treatment, where emissions peaked at 900 μg N m −2 h −1. Accumulated emissions ranged from 1.6 to 3.9 kg N 2O ha −1. A strong positive interaction between cover crop and tillage was observed. Soil concentration profiles of N 2O showed a significant accumulation of N 2O in CT relative to RT and DD treatments after spring tillage and slurry application, and a positive interaction between slurry and cover crop residues. A comparison in early May of N 2O emissions with flux estimates based on soil concentration profiles indicated that much of the N 2O emitted was produced near the soil surface. 相似文献
11.
Agricultural intensification has led to the use of very high inputs of nitrogen fertilizers into cultivated land. As a consequence of this, nitrous oxide (N 2O) emissions have increased significantly. Nowadays, the challenge is to mitigate these emissions in order to reduce global warming. Addition of nitrification inhibitors (NI) to fertilizers can reduce the losses of N 2O to the atmosphere, but field studies have shown that their efficiency varies depending greatly on the environmental conditions. Soil water content and temperature are key factors controlling N 2O emissions from soils and they seem to be also key parameters responsible for the variation in nitrification inhibitors efficiency. We present a laboratory study aimed at evaluating the effectiveness of the nitrification inhibitor 3,4-dimethylpyrazol phosphate (DMPP) at three different temperatures (10, 15 and 20 °C) and three soil water contents (40%, 60% and 80% of WFPS) on N 2O emissions following the application of 1.2 mg N kg −1 dry soil (equivalent to 140 kg N ha −1). Also the CO 2 and CH 4 emissions were followed to see the possible side effects of DMPP on the overall microbial activities. Nitrogen was applied either as ammonium sulfate nitrate (ASN) or as ENTEC 26 (ASN + DMPP). The application of ENTEC 26 was effective reducing N 2O losses up to the levels of an unfertilized control treatment in all conditions. Nevertheless, the percentage of reduction induced by DMPP in the ENTEC treatment with respect to the ASN varied from 3% to 45% depending on temperature and soil water content conditions. At 40% of WFPS, when nitrification is expected to be the main process producing N 2O, the increase of N 2O emissions in ASN together with temperature provoked an increase in DMPP efficiency reducing these emissions from 17% up to 42%. Contrarily, at 80% of WFPS, when denitrification is expected to be the main source of N 2O, emissions after ASN application decreased with temperature, which induced a decrease from 45% to 23% in the efficiency of DMPP reducing N 2O losses. Overall, the results obtained in this study suggest that DMPP performance regarding N 2O emissions reduction would be the best in cold and wet conditions. Neither CO 2 emissions nor CH 4 emissions were affected by the use of DMPP at the different soil water contents and temperatures. 相似文献
12.
Nitrous oxide emitted from urine patches is a key source of agricultural greenhouse gas emissions. A better understanding of the complex soil environmental and biochemical regulation of urine-N transformations in wet soils is needed to predict N 2O emissions from grazing and also to develop targeted mitigation technologies. Soil aeration, gas diffusion and drainage are key factors regulating N transformations and are affected by compaction during grazing. To understand how soil compaction from animal treading influences N transformations of urine in wet soils, we applied pressures of 0, 220 and 400 kPa to repacked soil cores, followed by 15N-labeled synthetic urine, and then subjected the cores to three successive saturation–drainage cycles on tension tables from 0 to 10 kPa.Compaction had a relatively small effect on soil bulk density (increasing from 0.81 to 0.88 Mg m −3), but strongly affected the pore size distribution. Compaction reduced both total soil porosity and macroporosity. It also affected the pore size distribution, principally by decreasing the proportion of 30–60 μm and 60–100 μm pores and increasing the proportion of micropores (<30 μm).Rates of urine-N transformations, emissions of N 2 and N 2O, and the N 2O to N 2 ratio were affected by the saturation/drainage cycles and degree of compaction. During the first saturation–drainage cycle, production of both N 2O and N 2 was low (<0.4 mg N m −2 h −1), probably because of anaerobic conditions inhibiting nitrification. In the second saturation/drainage cycle, the predominant product was N 2 at all compaction rates. By the third cycle, with increasing availability of mineral-N substrates, N 2O was the dominant product in the uncompacted (max = 4.70 mg N m −2 h −1) and 220 kPa compacted soils (max = 7.65 mg N m −2 h −1) with lower amounts of N 2 produced, while N 2 was produced in similar quantities to N 2O (max = 3.11 mg N m −2 h −1) in the 400 kPa compacted soil. Reduced macroporosity in the most compacted soil contributed to more sustained N 2 and N 2O production as the soils drained. In addition, compaction affected the rate of change of soil pH and DOC, both of which affected the N 2O to N 2 ratio.Denitrification during drainage and re-saturation may make a large contribution to soil N 2O emissions. Improving soil drainage and adopting grazing management practices that avoid soil compaction while increasing macroporosity will reduce total N 2O and N 2 emissions. 相似文献
13.
Few studies address nutrient cycling during the transition period (e.g., 1–4 years following conversion) from standard to some form of conservation tillage. This study compares the influence of minimum versus standard tillage on changes in soil nitrogen (N) stabilization, nitrous oxide (N 2O) emissions, short-term N cycling, and crop N use efficiency 1 year after tillage conversion in conventional (i.e., synthetic fertilizer-N only), low-input (i.e., alternating annual synthetic fertilizer- and cover crop-N), and organic (i.e., manure- and cover crop-N) irrigated, maize–tomato systems in California. To understand the mechanisms governing N cycling in these systems, we traced 15N-labeled fertilizer/cover crop into the maize grain, whole soil, and three soil fractions: macroaggregates (>250 μm), microaggregates (53–250 μm) and silt-and-clay (<53 μm). We found a cropping system effect on soil N new (i.e., N derived from 15N-fertilizer or - 15N-cover crop), with 173 kg N new ha −1 in the conventional system compared to 71.6 and 69.2 kg N new ha −1 in the low-input and organic systems, respectively. In the conventional system, more N new was found in the microaggregate and silt-and-clay fractions, whereas, the N new of the organic and low-input systems resided mainly in the macroaggregates. Even though no effect of tillage was found on soil aggregation, the minimum tillage systems showed greater soil fraction-N new than the standard tillage systems, suggesting greater potential for N stabilization under minimum tillage. Grain-N new was also higher in the minimum versus standard tillage systems. Nevertheless, minimum tillage led to the greatest N 2O emissions (39.5 g N 2O–N ha −1 day −1) from the conventional cropping system, where N turnover was already the fastest among the cropping systems. In contrast, minimum tillage combined with the low-input system (which received the least N ha −1) produced intermediate N 2O emissions, soil N stabilization, and crop N use efficiency. Although total soil N did not change after 1 year of conversion from standard to minimum tillage, our use of stable isotopes permitted the early detection of interactive effects between tillage regimes and cropping systems that determine the trade-offs among N stabilization, N 2O emissions, and N availability. 相似文献
14.
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 N 2O emissions and N 2O/(N 2O+N 2) 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–KNO 3, five split applications of 16 kg ha −1 N–KNO 3. Cumulative N 2O emissions for 22 days were unaffected by fertilization treatments at 32% water-filled pore space (WFPS). At 100% and 120%
WFPS, cumulative N 2O emissions were highest from soil fertilized with KNO 3. The split application of N fertilizers decreased N 2O emissions compared to a single initial application only when KNO 3 was applied to a saturated soil, at 100% WFPS. Emissions of N 2O were very low after the application of urea, similar to those found at unfertilized soil. Average N 2O/(N 2O+N 2) ratio values were significantly affected by moisture levels ( p = 0.015), being the lowest at 120% WFPS. The N 2O/(N 2O+N 2) ratio averaged 0.2 in unfertilized soil and 0.5 in fertilized soil, although these differences were not statistically significant. 相似文献
16.
Soil moisture and gaseous N-flux (N 2O, N 2) dynamics in Costa Rican coffee plantations were successively simulated using a mechanistic model (PASTIS) and two process-based models (NGAS and NOE). Two fertilized (250 kg N ha −1 y −1) coffee plantations were considered, namely a monoculture and a system shaded by the N 2 fixing legume species Inga densiflora. In situ N 2O fluxes were previously measured in these plantations. NGAS and NOE used specific microbial activities for the soils. To parameterize NGAS, we estimated N mineralization via in situ incubations and the contribution of heterotrophic soil respiration to total soil respiration. Potential denitrification rates and the proportion of denitrified N emitted as N 2O were measured in the laboratory to define the values of NOE parameters, as well as nitrification rates and related N 2O production rates for parameterizing both models. Soil moisture and both NGAS and NOE N 2O fluxes were best modelled on an hourly time step. Soil moisture dynamics were satisfactorily simulated by PASTIS. Simulated N 2O fluxes by both NGAS and NOE (3.2 and 2.1 kg N ha −1 y −1 for NGAS; 7.1 and 3.7 kg N ha −1 y −1 for NOE, for the monoculture and shaded plantations respectively) were within a factor of about 2 of the observed annual fluxes (4.3 and 5.8 kg N ha −1 y −1, for the monoculture and shaded plantations respectively). Statistical indicators of association and coincidence between simulated and measured values were satisfactory for both models. Nevertheless, the two models differed greatly in describing the nitrification and denitrification processes. Some of the algorithms in the model NGAS were apparently not applicable to these tropical acidic Andosols. Therefore, more detailed information about microbial processes in different agroecosystems would be needed, notably if process-oriented models were to be used for testing strategies for mitigating N 2O emissions. 相似文献
17.
The effects of compost application on soil carbon sequestration potential and carbon budget of a tropical sandy soil was studied. Greenhouse gas emissions from soil surface and agricultural inputs (fertiliser and fossil fuel uses) were evaluated. The origin of soil organic carbon was identified by using stable carbon isotope. The CO 2, CH 4 and N 2O emissions from soil were estimated in hill evergreen forest (NF) plot as reference, and in the corn cultivation plots with compost application rate at 30 Mg ha −1 y −1 (LC), and at 50 Mg ha −1 y −1 (HC). The total C emissions from soil surface were 8·54, 10·14 and 9·86 Mg C ha −1 y −1 for NF, HC and LC soils, respectively. Total N 2O emissions from HC and LC plots (2·56 and 3·47 kg N 2O ha −1 y −1) were significantly higher than from the NF plot (1·47 kg N 2O ha −1 y −1). Total CO 2 emissions from fuel uses of fertiliser, irrigation and machinery were about 10 per cent of total CO 2 emissions. For soil carbon storage, since 1983, it has been increased significantly (12 Mg ha −1) under the application of 50 Mg ha −1 y −1 of compost but not with 30 Mg ha −1 y −1. The net C budget when balancing out carbon inputs and outputs from soil for NF, HC and LC soils were +3·24, −2·50 and +2·07 Mg C ha −1 y −1, respectively. Stable isotope of carbon (δ 13C value) indicates that most of the increased soil carbon is derived from the compost inputs and/or corn biomass. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
18.
Intensive vegetable crop systems are rapidly developing, with consequences for greenhouse gas (GHGs) emissions, nitrogen leaching and soil carbon. We undertook a field trial to explore the effect of biochar application (0, 10, 20 and 40 t ha −1) on these factors in lettuce, water spinach and ice plant rotation. Our results show that the 20 and 40 t ha −1 soil treatments resulted in the SOC content being 26.3% and 29.8% higher than the control (0 t ha −1), respectively, with significant differences among all treatments ( p < .05). Biochar application caused N 2O emissions to decrease during the lettuce and water spinach seasons, by 1.5%–33.6% and 12.4%–40.5%, respectively, compared the control, with the 20 t ha −1 application rate resulting in the lowest N 2O emissions. Biochar also decreased the dissolved nitrogen (DN) concentration in leachate by 9.8%–36.2%, following a 7.3%–19.9% reduction in dissolved nitrogen in the soil. Similarly, biochar decreased the nitrate (NO 3−) concentrations in leachate by 3.9%–30.2%, following a 3.8%–16.7% reduction in the soil nitrate level. Overall, straw biochar applied at rate of 20 t ha −1 produced the lowest N 2O emissions and N leaching, while, increasing soil carbon. 相似文献
19.
In a 2-year field study, denitrification loss was measured from an irrigated sandy-clay loam under cotton receiving urea-N
at 158–173 kg ha –1. An acetylene inhibition-soil core method was employed for the direct measurement of denitrification, considering also the
N 2O entrapped in the soil. Taking into account the N 2O evolved from soil cores and that entrapped in the soil, a total of 65.7 kg N ha –1 and 64.4 kg N ha –1 was lost due to denitrification during the 1995 and 1996 cotton-growing seasons, respectively. Most (>70%) of the denitrification
loss occurred during June–August, a period characterized by high soil temperatures and heavy monsoon rains. On average, 35%
of the denitrification-N 2O was found entrapped in the soil and the amount of entrapped N 2O was significantly correlated with head space N 2O concentration and with water-filled pore space. 15N-balance during the 1996 growing season revealed a loss of 71.8 kg N ha –1. It was concluded that a substantial proportion of the fertilizer-N applied to irrigated cotton is lost under the semiarid
subtropical climatic conditions prevailing in the Central Punjab region of Pakistan and that denitrification is the major
N loss process under irrigated cotton in this region.
Received: 8 March 1999 相似文献
20.
The objective of this study is to evaluate different agricultural land‐use practices in terms of N leaching and to give recommendations for a sustainable agriculture on sandy soils in Middle Germany. Soil mineral N (N min) and leachate N were quantified at a sandy soil in N Saxony during 3 years. Two treatments were applied: intensive (I)—using inorganic and organic fertilizer and pesticides, and organic (O)—exclusively using organic fertilizer, legume‐based crop rotation, and no pesticides. Split application of mineral fertilizers did not result in substantial N losses at treatment I. Legumes induced a considerable increase of soil mineral N and particularly of leachate mineral N (N min_perc) at treatment O. High N min_perc concentrations (up to 78 mg N L –1) were observed during as well as after the cultivation of legumes. These high N min_perc concentrations are the reason why clearly higher N min_perc losses were determined at treatment O (62 kg N ha –1 y –1) compared to treatment I (23 kg N ha –1 y –1). At both treatments, the quantity of N losses was strongly affected by the precipitation rates. Concentrations and losses of dissolved organic N (DON perc) were assessed as above average at both treatments. The results suggest that the DON perc concentration is influenced by precipitation, soil coverage, and organic fertilizers. Higher values were determined in the percolation water of treatment O. The average annual DON perc losses amounted to 15 kg N ha –1 at I and to 32 kg N ha –1 at O. The average monthly percentage of DON perc losses on the loss of the dissolved total N of percolation water (DTN perc) ranged between <1% and 55% at O and between 2% and 56% at I. For the whole measuring period of 29 months, the relative amounts of DON perc of DTN perc (21% at O and 25% at I) were more or less the same for both treatments. The results show that DON perc can contribute significantly to the total N loss, confirming the importance to consider this N fraction in N‐leaching studies. It was concluded that at sandy sites, a split application of mineral fertilizers, as applied at treatment I, seems to be more expedient for limiting the N leaching losses than legume‐based crop rotations. 相似文献
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