scholarly journals The influence of tillage on N<sub>2</sub>O fluxes from an intensively managed grazed grassland in Scotland

2016 ◽  
Vol 13 (16) ◽  
pp. 4811-4821 ◽  
Author(s):  
Nicholas J. Cowan ◽  
Peter E. Levy ◽  
Daniela Famulari ◽  
Margaret Anderson ◽  
Julia Drewer ◽  
...  

Abstract. Intensively managed grass production in high-rainfall temperate climate zones is a globally important source of N2O. Many of these grasslands are occasionally tilled to rejuvenate the sward, and this can lead to increased N2O emissions. This was investigated by comparing N2O fluxes from two adjacent intensively managed grazed grasslands in Scotland, one of which was tilled. A combination of eddy covariance, high-resolution dynamic chamber and static chamber methods was used. N2O emissions from the tilled field increased significantly for several days immediately after ploughing and remained elevated for approximately 2 months after the tillage event contributing to an estimated increase in N2O fluxes of 0.85 ± 0.11 kg N2O-N ha−1. However, any influence on N2O emissions after this period appears to be minimal. The cumulative N2O emissions associated with the tillage event and a fertiliser application of 70 kg N ammonia nitrate from one field were not significantly different from the adjacent untilled field, in which two fertiliser applications of 70 kg N ammonia nitrate occurred during the same period. Total cumulative fluxes calculated for the tilled and untilled fields over the entire 175-day measurement period were 2.14 ± 0.18 and 1.65 ± 1.02 kg N2O-N ha−1, respectively.

2016 ◽  
Author(s):  
N.J. Cowan ◽  
P.E. Levy ◽  
D. Famulari ◽  
M. Anderson ◽  
J. Drewer ◽  
...  

Abstract. Intensively managed grass production in high rainfall temperate climate zones is a globally important source of N2O. Many of these grasslands are occasionally tilled and can lead to increased N2O emissions. This was investigated by comparing N2O fluxes from two adjacent intensively managed grazed grasslands in Scotland, one of which was tilled. A combination of eddy covariance, high resolution dynamic chamber and static chamber methods greatly improved the temporal and spatial coverage of N2O fluxes before and after the tillage event and is recommended to be followed in future studies. Total cumulative fluxes calculated for the tilled and un-tilled fields over the 175 day measurement period were 2.45 ± 0.27 and 2.08 ± 0.23 kg N2O-N ha−1, respectively. N2O emissions from the tilled field increased significantly for several days immediately after ploughing and remained elevated for approximately two months after the tillage event contributing to an estimated increase in N2O fluxes of 1.08 ± 0.14 kg N2O-N ha−1. Cumulative fluxes calculated over a 28 day period in August after the application of 70 kg-N ha−1 as ammonium nitrate to both fields were estimated at 0.42 ± 0.15 and 0.75 ± 0.14 kg N2O N ha−1 for the tilled and un-tilled fields, respectively. The tillage event appears to have substantially increased N2O fluxes from the tilled grassland field over a two month period; however, this increase may have been fractionally offset by a decrease in emissions after the August fertilisation event.


2013 ◽  
Vol 10 (2) ◽  
pp. 2635-2673 ◽  
Author(s):  
D. Imer ◽  
L. Merbold ◽  
W. Eugster ◽  
N. Buchmann

Abstract. A profound understanding of temporal and spatial variabilities of CO2, CH4 and N2O fluxes between terrestrial ecosystems and the atmosphere is needed to reliably quantify these fluxes and to develop future mitigation strategies. For managed grassland ecosystems, temporal and spatial variabilities of these three greenhouse gas (GHG) fluxes are due to environmental drivers as well as to fertilizer applications, grazing and cutting events. To assess how these affect GHG fluxes at Swiss grassland sites, we studied three sites along an altitudinal gradient that corresponds to a management gradient: from 400 m a.s.l. (intensively managed) to 1000 m a.s.l. (moderately intensive managed) to 2000 m a.s.l. (extensively managed). Temporal and spatial variabilities of GHG fluxes were quantified along small-scale transects of 16 static soil chambers at each site. We then established functional relationships between drivers and the observed fluxes on diel and annual time scales. Furthermore, spatial variabilities and their effect on representative site-specific mean chamber GHG fluxes were assessed using geostatistical semivariogram approaches. All three grasslands were N2O sources, with mean annual fluxes ranging from 0.15 to 1.28 nmol m−2 s−1. Contrastingly, all sites were net CH4 sinks, with uptake rates ranging from −0.56 to −0.15 nmol m−2 s−1. Mean annual respiration losses of CO2, as measured with opaque chambers, ranged from 5.2 to 6.5 μmol m−2 s−1. While the environmental drivers and their respective explanatory power for N2O emissions differed considerably among the three grasslands (adjusted r2 ranging from 0.19 to 0.42), CH4 and CO2 fluxes were much better constrained (adjusted r2 ranging from 0.41 to 0.83), in particular by soil water content and air temperature, respectively. Throughout the year, spatial heterogeneity was particularly high for N2O and CH4 fluxes. We found permanent hot spots for N2O emissions and CH4 uptake at the extensively managed site. Including these hot spots in calculating the mean chamber flux was essential to obtain a representative mean flux for this ecosystem. At the intensively managed grassland, management effects clearly dominated over effects of environmental drivers on N2O fluxes. For CO2 and CH4, the importance of management effects did depend on the status of the vegetation.


2014 ◽  
Vol 11 (11) ◽  
pp. 15327-15360
Author(s):  
N. J. Cowan ◽  
P. Norman ◽  
D. Famulari ◽  
P. E. Levy ◽  
D. S. Reay ◽  
...  

Abstract. One hundred N2O flux measurements were made from an area of intensively managed grazed grassland in central Scotland using a high resolution dynamic chamber method. The field contained a variety of features from which N2O fluxes were measured including a manure heap, patches of decaying grass silage, and areas of increased sheep activity. Individual fluxes varied significantly across the field varying from 2 to 79 000 μg N2O-N m−2 h−1. Soil samples were collected at 55 locations to investigate relationships between soil properties and N2O flux. Fluxes of N2O correlated strongly with soil NO3− concentrations. Distribution of NO3− and the high spatial variability of N2O flux across the field are shown to be linked to the distribution of waste from grazing animals and the resultant reactive nitrogen compounds in the soil which are made available for microbiological processes. Features within the field such as shaded areas and manure heaps contained significantly higher available nitrogen than the rest of the field. Although these features only represented 1.1% of the area of the field, they contributed to over 55% of the total estimated daily N2O flux.


2018 ◽  
Vol 15 (18) ◽  
pp. 5519-5543 ◽  
Author(s):  
Kathrin Fuchs ◽  
Lukas Hörtnagl ◽  
Nina Buchmann ◽  
Werner Eugster ◽  
Val Snow ◽  
...  

Abstract. Replacing fertiliser nitrogen with biologically fixed nitrogen (BFN) through legumes has been suggested as a strategy for nitrous oxide (N2O) mitigation from intensively managed grasslands. While current literature provides evidence for an N2O emission reduction effect due to reduced fertiliser input, little is known about the effect of increased legume proportions potentially offsetting these reductions, i.e. by increased N2O emissions from plant residues and root exudates. In order to assess the overall effect of this mitigation strategy on permanent grassland, we performed an in situ experiment and quantified net N2O fluxes and biomass yields in two differently managed grass–clover mixtures. We measured N2O fluxes in an unfertilised parcel with high clover proportions vs. an organically fertilised control parcel with low clover proportions using the eddy covariance (EC) technique over 2 years. Furthermore, we related the measured N2O fluxes to management and environmental drivers. To assess the effect of the mitigation strategy, we measured biomass yields and quantified biologically fixed nitrogen using the 15N natural abundance method. The amount of BFN was similar in both parcels in 2015 (control: 55±5 kg N ha−1 yr−1; clover parcel: 72±5 kg N ha−1 yr−1) due to similar clover proportions (control: 15 % and clover parcel: 21 %), whereas in 2016 BFN was substantially higher in the clover parcel compared to the much lower control (control: 14±2 kg N ha−1 yr−1 with 4 % clover in DM; clover parcel: 130±8 kg N ha−1 yr−1 and 44 % clover). The mitigation management effectively reduced N2O emissions by 54 % and 39 % in 2015 and 2016, respectively, corresponding to 1.0 and 1.6 t ha−1 yr−1 CO2 equivalents. These reductions in N2O emissions can be attributed to the absence of fertilisation on the clover parcel. Differences in clover proportions during periods with no recent management showed no measurable effect on N2O emissions, indicating that the decomposition of plant residues and rhizodeposition did not compensate for the effect of fertiliser reduction on N2O emissions. Annual biomass yields were similar under mitigation management, resulting in a reduction of N2O emission intensities from 0.42 g N2O-N kg−1 DM (control) to 0.28 g N2O-N kg−1 DM (clover parcel) over the 2-year observation period. We conclude that N2O emissions from fertilised grasslands can be effectively reduced without losses in yield by increasing the clover proportion and reducing fertilisation.


2018 ◽  
Author(s):  
Kathrin Fuchs ◽  
Lukas Hörtnagl ◽  
Nina Buchmann ◽  
Werner Eugster ◽  
Valerie Snow ◽  
...  

Abstract. Replacing fertilizer nitrogen with biological nitrogen fixation (BNF) through legumes has been suggested as a strategy for nitrous oxide (N2O) mitigation from intensively managed grasslands. While current literature provides evidence for an N2O emission reduction effect due to reduced fertilizer input, little is known about the effect of increased legume proportions potentially offsetting these reductions, i.e. by increased N2O emissions from plant residues and root exudates. In order to assess the overall effect of this mitigation strategy on permanent grassland, we performed an in-situ experiment to quantify net N2O fluxes and biomass yields in two differently managed grass-clover mixtures. We measured N2O fluxes in an unfertilized parcel with high clover proportions vs. a fertilized control parcel with low clover proportions using the eddy–covariance (EC) technique over two years. Furthermore, we related the measured N2O fluxes to management and environmental drivers. To assess the effect of the mitigation strategy, we measured biomass yields and quantified biologically fixed nitrogen using the 15N natural abundance method. The mitigation management effectively reduced N2O emissions by 54 % and 39 % in 2015 and 2016, respectively. These reductions in N2O emissions can be attributed to the absence of fertilization on the clover parcel. Differences in clover proportions during periods with no recent management showed no measurable effect on N2O emissions, indicating that decomposition of plant residues and rhizodeposition did not compensate the effect of fertilizer reduction on N2O emissions. Annual biomass yields were similar under mitigation management, resulting in a reduction of N2O emission intensities from 0.42 g N2O-N kg−1 DM (control) to 0.28 g N2O-N kg−1 DM (clover parcel) over the two years observation period. We conclude that N2O emissions from fertilized grasslands can be effectively reduced without losses in yield by increasing the clover proportion and reducing fertilization.


2013 ◽  
Vol 10 (9) ◽  
pp. 5931-5945 ◽  
Author(s):  
D. Imer ◽  
L. Merbold ◽  
W. Eugster ◽  
N. Buchmann

Abstract. A profound understanding of temporal and spatial variabilities of soil carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes between terrestrial ecosystems and the atmosphere is needed to reliably quantify these fluxes and to develop future mitigation strategies. For managed grassland ecosystems, temporal and spatial variabilities of these three soil greenhouse gas (GHG) fluxes occur due to changes in environmental drivers as well as fertilizer applications, harvests and grazing. To assess how such changes affect soil GHG fluxes at Swiss grassland sites, we studied three sites along an altitudinal gradient that corresponds to a management gradient: from 400 m a.s.l. (intensively managed) to 1000 m a.s.l. (moderately intensive managed) to 2000 m a.s.l. (extensively managed). The alpine grassland was included to study both effects of extensive management on CH4 and N2O fluxes and the different climate regime occurring at this altitude. Temporal and spatial variabilities of soil GHG fluxes and environmental drivers on various timescales were determined along transects of 16 static soil chambers at each site. All three grasslands were N2O sources, with mean annual soil fluxes ranging from 0.15 to 1.28 nmol m−2 s−1. Contrastingly, all sites were weak CH4 sinks, with soil uptake rates ranging from −0.56 to −0.15 nmol m−2 s−1. Mean annual soil and plant respiration losses of CO2, measured with opaque chambers, ranged from 5.2 to 6.5 μmol m−2 s−1. While the environmental drivers and their respective explanatory power for soil N2O emissions differed considerably among the three grasslands (adjusted r2 ranging from 0.19 to 0.42), CH4 and CO2 soil fluxes were much better constrained (adjusted r2 ranging from 0.46 to 0.80) by soil water content and air temperature, respectively. Throughout the year, spatial heterogeneity was particularly high for soil N2O and CH4 fluxes. We found permanent hot spots for soil N2O emissions as well as locations of permanently lower soil CH4 uptake rates at the extensively managed alpine site. Including hot spots was essential to obtain a representative mean soil flux for the respective ecosystem. At the intensively managed grassland, management effects clearly dominated over effects of environmental drivers on soil N2O fluxes. For CO2 and CH4, the importance of management effects did depend on the status of the vegetation (LAI).


2015 ◽  
Vol 12 (5) ◽  
pp. 1585-1596 ◽  
Author(s):  
N. J. Cowan ◽  
P. Norman ◽  
D. Famulari ◽  
P. E. Levy ◽  
D. S. Reay ◽  
...  

Abstract. One hundred N2O flux measurements were made from an area of intensively managed grazed grassland in central Scotland using a high-resolution dynamic chamber method. The field contained a variety of features from which N2O fluxes were measured including a manure heap, patches of decaying grass silage, and areas of increased sheep activity. Individual fluxes varied significantly across the field varying from 2 to 79 000 μg N2O-N m−2 h−1. Soil samples were collected at 55 locations to investigate relationships between soil properties and N2O flux. Fluxes of N2O correlated strongly with soil NO3- concentrations. Distribution of NO3− and the high spatial variability of N2O flux across the field are shown to be linked to the distribution of waste from grazing animals and the resultant reactive nitrogen compounds in the soil which are made available for microbiological processes. Features within the field such as shaded areas and manure heaps contained significantly higher available nitrogen than the rest of the field. Although these features only represented 1.1% of the area of the field, they contributed to over 55% of the total estimated daily N2O flux.


Parasitology ◽  
2020 ◽  
pp. 1-5
Author(s):  
Chatree Chumnandee ◽  
Nawarat Pha-obnga ◽  
Oskar Werb ◽  
Kai Matuschewski ◽  
Juliane Schaer

Abstract Parasites of the haemosporidian genus Polychromophilus have exclusively been described in bats. These parasites belong to the diverse group of malaria parasites, and Polychromophilus presents the only haemosporidian taxon that infects mammalian hosts in tropical as well as in temperate climate zones. This study provides the first information of Polychromophilus parasites in the lesser Asiatic yellow bat (Scotophilus kuhlii) in Thailand, a common vespertilionid bat species distributed in South and Southeast Asia. The gametocyte blood stages of the parasites could not be assigned to a described morphospecies and molecular analysis revealed that these parasites might represent a distinct Polychromophilus species. In contrast to Plasmodium species, Polychromophilus parasites do not multiply in red blood cells and, thus, do not cause the clinical symptoms of malaria. Parasitological and molecular investigation of haemosporidian parasites of wildlife, such as the neglected genus Polychromophilus, will contribute to a better understanding of the evolution of malaria parasites.


Author(s):  
Qi Wei ◽  
Junzeng Xu ◽  
Linxian Liao ◽  
Yawei Li ◽  
Haiyu Wang ◽  
...  

To reveal the effect of irrigation salinity on soil nitrous oxide (N2O) emission, pot experiments were designed with three irrigation salinity levels (NaCl and CaCl2 of 1, 2.5 and 4 g/L equivalence, Ec = 3.6, 8.1 and 12.7 ds/m), either for 0 kg N/ha (N0) or 120 kg N/ha (N120) nitrogen inputs. N2O emissions from soils irrigated at different salinity levels varied in a similar pattern which was triggered by soil moisture dynamics. Yet, the magnitudes of pulse N2O fluxes were significantly varied, with the peak flux at 5 g/L irrigation salinity level being much higher than at 2 and 8 g/L. Compared to fresh water irrigated soils, cumulative N2O fluxes were reduced by 22.7% and 39.6% (N0), 29.1% and 39.2% (N120) for soils irrigated with 2 and 8 g/L saline water, while they were increased by 87.7% (N0) and 58.3% (N120) for soils irrigated with 5 g/L saline water. These results suggested that the effect degree of salinity on consumption and production of N2O might vary among irrigation salinity ranges. As such, desalinating brackish water to a low salinity level (such as 2 g/L) before it is used for irrigation might be helpful for solving water resources crises and mitigating soil N2O emissions.


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