Emission of Gas and Dust from Livestock
SOIL APPLICATION OF ACIDIFIED SLURRY AS ALTERNATIVE TO RAW CATTLE-SLURRY INJECTION TO MINIMISE GASEOUS EMISSIONS IN MEDITERANEAN CONDITIONS
FANGUEIRO, D.1, PEREIRA, J.L.S.2, SURGY, S.1, VASCONCELOS, E.1, COUTINHO, J.3
1 LEAF, Instituto Superior de Agronomia, Universidade de Lisboa, Lisboa, Portugal
2 ESAV, Polytechnic Institute of Viseu, Portugal
3 Chemistry Centre, University of Trás-os-Montes and Alto Douro, Vila Real, Portugal
ABSTRACT: The objective of this study was to compare N and C emissions from two contrasting soils following band application of acidified cattle-slurry (ASS) or raw cattle-slurry injection (SI) in Mediterranean conditions. Band application of raw cattle-slurry followed by incorporation (SS) was also considered as the traditional method and the impact of acidified slurry incorporation in soil following band application was also tested (AS). For this, a double cropping system (maize followed by oat) was run over 3-years in 1 m×1 m plots from a sandy (S) and a sandy-loam (SL) soil. The NH3 fluxes were measured by the dynamic chamber technique during the first 96 h after slurry application, while the N2O, CO2 and CH4 fluxes were measured during the whole experiment by the closed chamber technique. The results showed that slurry acidification has no negative impact on N2O emissions with similar values observed in SS, AS and ASS during both oat and maize growth while significantly higher values were observed in SI than in other amended treatments during maize growth . When considering cumulative GHG emissions, no significant differences were observed between SI, AS and ASS in both soils indicating that application of acidified slurry has no negative impact on GHG emissions. Thus, band application of acidified slurry can be considered as a good alternative to slurry injection to minimise gaseous emissions at field scale in Mediterranean conditions.
Keywords: Acidification, Cattle-slurry, Gaseous emissions, Injection, Mitigation strategy
INTRODUCTION: Nowadays, slurry injection is the recommended method to minimise NH3
emissions but its impact on other gases as N2O is not clear and such technique is not always applicable, namely in stony soils or small plots. Slurry acidification is efficient to minimise NH3 emissions along the slurry management chain but application of acidified slurry is still limited to Denmark and other countries from North Europe (Fangueiro et al., 2015a).
Information about the impact of acidified slurry application to soil on gaseous emissions (NH3 and GHG) in Mediterranean conditions are still scarce or inexistent. Our main hypothesis is that band application of acidified slurry is almost as efficient as slurry injection to minimise gaseous emissions at field scale. Hence, the objective of the present study was to compare NH3 and GHG emissions from two different soils following band application of acidified cattle-slurry (ASS) or raw cattle-slurry injection (H=100 mm) (SI) in Mediterranean conditions. Band application of raw cattle-slurry followed by incorporation (H=20 mm) (SS) was also considered as the traditional method and the impact of acidified slurry incorporation in soil following band application was also tested (AS). An unfertilised plot (Control) was included.
1. MATERIAL AND METHODS:
1.1. Experimental: The experiment was carried out at the Instituto Superior de Agronomia (Lisboa, Portugal) (Figure 1). A double-cropping forage system producing oat (November to
Mitigation strategies
Mars) and maize (May to July) was run over 3-years (September-2012 to July-2015) in 1 m×1 m plots from a sandy (Haplic Arenosol) (S) and a sandy loam (Haplic Cambisol) (SL) soil. The rates of slurries applied were ca. 90 kg N ha-1 in November (oat crop) and ca. 170 kg N ha-1 in May (maize crop). The slurry acidification was performed by addition of concentrated sulphuric acid to reach a final pH of 5.5 (Fangueiro et al., 2015b). Experimental conditions used here were similar to those described in (Fangueiro et al., 2015c).
Figure 1. Location of the field experiment (latitude: 38.708059º, longitude: -9.185058º).
1.2. Measurements and data analysis: The NH3 fluxes were measured during the first 96 h after soil amendment before the sowing of each forage crop, by the dynamic chamber technique using acid traps (0.05 M H3PO4). The N2O, CO2 and CH4 fluxes were measured daily in the first 7 days after application and then every 3 days until harvest of each forage crop, by the closed chamber technique with gas concentration determination by gas chromatography (GC-2014, Shimadzu) (Fangueiro et al., 2015c). Data were subjected to analysis of variance and Tukey comparisons of means tests were carried out using the statistical software package Statistix.
2. RESULTS AND DISCUSSION:
2.1. Ammonia emissions: The average amount of NH3 emitted from each treatment in each
Sandy soil
Figure 2. Average amount of NH3 emitted during each crop growth and during the whole experiment. Error bars represent the standard error values used for comparison in the Tukey test at each crop (n=3).
2.2. Greenhouse gases emissions: The dynamics of N2O emissions were different in both soils when comparing amended treatments (data not showed): SI led to higher and earlier peaks of N2O relative to AS or ASS. During maize cycle, the highest (p<0.05) N2O emissions were measured in SI but, during oat cycle, N2O emission rates observed in SS, SI, AS and ASS were not significantly different (P<0.05) (Figure 3). Thus, it can be concluded that slurry acidification has no negative impact on N2O emissions after soil application and that it can even decrease N2O emissions relative to SI during maize growth. The cumulative GHG emissions observed in amended treatments (Figure 4) were not significantly different (P<0.05) during oat growth in both soils and during maize growth in the sandy soil. However, in the sandy loam soil, SI and AS led to significantly higher values than in SS. Hence, in this last case, it might be of interest to incorporate the acidified slurry applied on soil surface to minimize GHG emissions.
Figure 3. Average amount of N2O emitted during each crop growth and during the whole experiment. Error bars represent the standard error values used for comparison in the Tukey test at each crop (n=3).
Figure 4. Average value of cumulative GHG emissions observed for each crop. Error bars represent the standard error values used for comparison in the Tukey test at each crop (n=3).
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3. CONCLUSION: Band application of acidified raw slurry (AWS) is as efficient as slurry injection to minimise NH3 emissions and there is no need to immediate soil incorporation.
Raw slurry injection increased N2O emissions during maize growth while AWS application led to emissions similar to non acidified slurry applied on soil surface. Furthermore, a delay or reduction/inhibition of nitrification occurred in soil amended with AWS. The increase of methane emissions relative to WSS observed in WSI and AWSS but not in AWSM indicated that AWS incorporation immediately after soil application might contribute to minimize CH4 emissions. It can then be concluded that band application of acidified raw slurry followed by incorporation is a potential alternative to raw slurry injection relative to the gaseous emissions issue but an overall evaluation is still required to avoid potential pollution swapping.
Acknowledgements: The study was funded by project PTDC/AGR-PRO/119428/2010.
REFERENCES:
Fangueiro D., Hjorth M., Gioelli F., 2015a. Acidification of animal slurry - a review. J. Environ.
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Fangueiro D., Pereira J., Bichana A., Surgy S., Cabral F., Coutinho J., 2015b. Effects of cattle-slurry treatment by acidification and separation on nitrogen dynamics and global warming potential after soil surface application to an acidic soil. J. Environ. Manag., 162, 1-8.
Fangueiro D., Surgy S., Fraga I., Cabral F., Coutinho J., 2015c. Band application of treated cattle slurry as an alternative to slurry injection: Implications for gaseous emissions, soil quality and plant growth. Agric. Ecosyst. Environ., 211, 102-111.
INCLUSION OF OLIVE CAKE IN FATTENING PIG FEEDS: EFFECTS ON AMMONIA AND