Roman Hüppi

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Hüppi

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Roman

ORCID

0000-0001-8815-7835

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Publications 1 - 10 of 12

Carbon Dioxide Removal Policies for a Net Zero Switzerland and Beyond. Policy Pathways and Visions
Brazzola, Nicoletta; Eberenz, Samuel; Honegger, Matthias; et al. (2023)
CDR Swiss White Paper
Effect of biochar and liming on soil nitrous oxide emissions from a temperate maize cropping system
Hüppi, Roman; Felber, Raphael; Neftel, Albrecht; et al. (2015)
Soil
Biochar, a carbon-rich, porous pyrolysis product of organic residues may positively affect plant yield and can, owing to its inherent stability, promote soil carbon sequestration when amended to agricultural soils. Another possible effect of biochar is the reduction in emissions of nitrous oxide (N2O). A number of laboratory incubations have shown significantly reduced N2O emissions from soil when mixed with biochar. Emission measurements under field conditions however are more scarce and show weaker or no reductions, or even increases in N2O emissions. One of the hypothesised mechanisms for reduced N2O emissions from soil is owing to the increase in soil pH following the application of alkaline biochar. To test the effect of biochar on N2O emissions in a temperate maize cropping system, we set up a field trial with a 20t ha−1 biochar treatment, a limestone treatment adjusted to the same pH as the biochar treatment (pH 6.5), and a control treatment without any addition (pH 6.1). An automated static chamber system measured N2O emissions for each replicate plot (n = 3) every 3.6 h over the course of 8 months. The field was conventionally fertilised at a rate of 160 kg N ha−1 in three applications of 40, 80 and 40 kg N ha−1 as ammonium nitrate. Cumulative N2O emissions were 52 % smaller in the biochar compared to the control treatment. However, the effect of the treatments overall was not statistically significant (p = 0.27) because of the large variability in the data set. Limed soils emitted similar mean cumulative amounts of N2O as the control. There is no evidence that reduced N2O emissions with biochar relative to the control is solely caused by a higher soil pH.
Soil greenhouse gas fluxes following tropical deforestation for fertilizer-intensive sugarcane cultivation in northwestern Uganda
Tamale, Joseph; Van Straaten, Oliver; Hüppi, Roman; et al. (2022)
EGUsphere
Deforestation followed by fertilizer intensive agriculture is widely recognized as a significant contributor to anthropogenic greenhouse gas emissions (GHG), particularly carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). However, empirical studies focusing on soil GHG flux dynamics from deforestation hotspots in the tropics are still limited creating major uncertainties for constraining global GHG budgets. In this study, we investigated how deforestation for fertilizer intensive sugarcane cultivation in Uganda affects soil-borne GHGs. Therefore, soil GHG fluxes were measured in a primary forest and in a completely randomized experiment premised in the neighboring sugarcane fields with different fertilizer regimes, representing both smallholder and industrial-scale sugarcane farm management. Despite the use of different fertilization rates (low, standard, and high) as treatments for the sugarcane CRD experiment, neither auxiliary controls nor soil GHG fluxes significantly differed among the CRD treatments. Soil respiration was higher in the sugarcane than in the forest, which we attribute to the increased autotrophic respiration from the sugarcane’s fine root biomass and the likely exposure of the sugarcane’s larger soil organic carbon stocks to microbial decomposition through ploughing operations. The forest soils were a stronger net sink of CH4 than the sugarcane soils despite forest soils having both higher bulk densities and larger water-filled pore space (WFPS), and we suspect that this was due to alteration of the methanotroph abundance upon the conversion. Soil N2O emissions were smaller in the sugarcane than in the forest, which was surprising, but most likely resulted from the excess N being lost either through leaching or uptake by the sugarcane crop. Only seasonal variability in WFPS, among the auxiliary controls, affected CH4 uptake at both sites and soil CO2 effluxes in the sugarcane. Noteworthy, soil N2O fluxes from both sites were unaltered by the seasonality-mediated changes in auxiliary controls. All the findings put together suggest that forest conversion for sugarcane cultivation alters soil GHG fluxes by increasing soil CO2 emissions and reducing both soil CH4 sink strength and soil N2O emissions.
Editorial: Agricultural diversification: Benefits and barriers for sustainable soil management
Francaviglia, Rosa; Almagro, María; Lehtonen, Heikki; et al. (2022)
Frontiers in Environmental Science
Crop Diversification in Viticulture with Aromatic Plants: Effects of Intercropping on Grapevine Productivity in a Steep-Slope Vineyard in the Mosel Area, Germany
Dittrich, Felix; Iserloh, Thomas; Treseler, Cord-Henrich; et al. (2021)
Agriculture
The effects of intercropping grapevine with aromatic plants are investigated using a multi-disciplinary approach. Selected results are presented that address the extent to which crop diversification by intercropping impacts grapevine yield and must quality, as well as soil water and mineral nutrients (NO3-N, NH4-N, plant-available K and P). The experimental field was a commercial steep-slope vineyard with shallow soils characterized by a high presence of coarse rock fragments in the Mosel area of Germany. The field experiment was set up as randomized block design. Rows were either cultivated with Riesling (Vitis vinifera L.) as a monocrop or intercropped with Origanum vulgare or Thymus vulgaris. Regarding soil moisture and nutrient levels, the topsoil (0–0.1 m) was more affected by intercropping than the subsoil (0.1–0.3 m). Gravimetric moisture was consistently lower in the intercropped topsoil. While NO3-N was almost unaffected by crop diversification, NH4-N, K, and P were uniformly reduced in topsoil. Significant differences in grapevine yield and must quality were dominantly attributable to climate variables, rather than to the treatments. Yield stabilization due to intercropping with thyme and oregano seems possible with sufficient rainfall or by irrigation. The long-term effects of intercropping on grapevine growth need further monitoring.
Nutrient limitations regulate soil greenhouse gas fluxes from tropical forests: evidence from an ecosystem-scale nutrient manipulation experiment in Uganda
Tamale, Joseph; Hüppi, Roman; Griepentrog, Marco; et al. (2021)
Soil Discussions
Tropical forests contribute significantly to the emission and uptake of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). However, studies on the soil environmental controls of greenhouse gases (GHGs) from African tropical forest ecosystems are still rare. The aim of this study was to disentangle the regulation effect of soil nutrients on soil GHG fluxes in a tropical forest in northwestern Uganda. Therefore, a large-scale nutrient manipulation experiment (NME) based on 40 m × 40 m plots with different nutrient addition treatments (nitrogen (N), phosphorus (P), N + P, and control) was established. Soil CO2, CH4, and N2O fluxes were measured monthly using permanently installed static chambers for 14 months. Total soil CO2 fluxes were partitioned into autotrophic and heterotrophic components through a root trenching treatment. In addition, soil temperature, soil water content, and mineral N were measured in parallel to GHG fluxes. N addition (N, N + P) resulted in significantly higher N2O fluxes in the transitory phase (0–28 days after fertilization, p < 0.01), because N fertilization likely increased soil N beyond the microbial immobilization and plant nutritional demands leaving the excess to be nitrified or denitrified. Prolonged N fertilization however, did not elicit a significant response in background (measured more than 28 days after fertilization) N2O fluxes. P fertilization marginally and significantly increased transitory (p = 0.052) and background (p = 0.010) CH4 consumption, probably because it enhanced methanotrophic activity. Addition of N and P together (N + P) resulted in larger CO2 fluxes in the transitory phase (p = 0.010), suggesting a possible co-limitation of N and P on soil respiration. Heterotrophic (microbial) CO2 effluxes were significantly higher than the autotrophic (root) CO2 effluxes (p < 0.001) across all treatment plots with microbes contributing about three times more to the total soil CO2 effluxes compared to roots (p < 0.001). However, neither heterotrophic nor autotrophic respiration significantly differed between treatments. The results from this study suggest that the feedback of tropical forests to the global soil GHG budget could be disproportionately altered by changes in N and P availability in these biomes.
Relationship between greenhouse gas emissions and changes in soil gas diffusivity in a field experiment with biochar and lime
Keller, Thomas; Hüppi, Roman; Leifeld, Jens (2019)
Journal of Plant Nutrition and Soil Science
Evaluating the role soil nutrients play in regulating soil greenhouse gas fluxes from the pristine tropical forests: evidence from a nutrient manipulation experiment in Uganda
Tamale, Joseph; Hüppi, Roman; Griepentrog, Marco; et al. (2021)
EGUsphere
The exchange of the climate-relevant greenhouse gases (GHGs) at the soil-atmospheric interface is regulated by both abiotic and biotic controls. However, evidence on nutrient limitations of soil GHG fluxes from African tropical forest ecosystems is still rare. Therefore, an ecosystem-scale nutrient manipulation experiment (NME) consisting of nitrogen (N), phosphorus (P), N + P, and control treatments was set up in a tropical forest in northwestern Uganda. Soil carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) fluxes were measured monthly using static vented chambers for 14 months. A root trenching treatment was also done in all the experimental plots in order to disentangle the contribution of root and microbial respiration to total soil CO2 effluxes. In parallel to soil GHG flux measurements, soil temperature, soil moisture, and mineral N were determined. Lifting the N limitation on the soil nitrifiers and denitrifiers through N fertilization significantly increased N2O fluxes in N, and N + P addition plots in the transitory phase (0-28 days after N fertilization, p < 0.01). However, sustained N fertilization did not significantly affect background (measured more than 28 days after fertilization) N2O fluxes. Alleviation of the P limitation on soil methanotrophs through P fertilization marginally and significantly increased CH4 consumption in the transitory (p = 0.052) and background (p = 0.010) phases, respectively. Simultaneous addition of N and P (N + P) significantly affected transitory soil CO2 effluxes (p = 0.010), suggesting a possible co-limitation of N and P on soil respiration. Microbial CO2 effluxes were significantly larger than root CO2 effluxes (p < 0.001) across all treatment plots so was the contribution of microbial respiration to the total soil CO2 effluxes (about 70 %, p < 0.001). Despite the fact that soil respiration was affected through N + P fertilization, neither heterotrophic nor autotrophic respiration significantly differed in either the N + P or the other treatments. Overall, the study findings suggest that the contribution of tropical forests to the global soil GHG budget could be altered by changes in N and P availability in these biomes.
Soil Nitrous Oxide Emission and Methane Exchange From Diversified Cropping Systems in Pannonian Region
Hüppi, Roman; Horváth, László; Dezső, József; et al. (2022)
Frontiers in Environmental Science
Diversified farming systems are promoted to improve ecosystem services in agriculture while maintaining productivity. Intercropping could improve soil quality, the stability of yields and climate resilience. Whether direct emissions of greenhouse gases from soil are reduced as well, depends on the specific measures of diversification. Here, we determined the greenhouse gas emissions from soils of two diversification experiments in the Pannonian climate of Hungary. Firstly, in an asparagus field, oat and field pea was introduced as intercrop between the asparagus berms. Secondly, grass and aromatic herbs were intercropped in a vineyard between the grape rows. The results show that especially for nitrous oxide, average treatment emissions can increase with additional legumes (+252% with intercropped field peas) but decrease with aromatic herbs (−66%). No significant changes were found for methane exchange. This shows that, while other ecosystem services can be increased by intercropping, changes in soil greenhouse gas emissions by intercropping are highly context dependent.
Emissions of nitrous oxide and methane after field application of liquid organic fertilizers and biochar
Efosa, Norah; Krause, Hans-Martin; Hüppi, Roman; et al. (2023)
Agriculture, Ecosystems & Environment
The use of anaerobic digestates as fertilizer is proposed as a means to close agricultural nutrient cycles. However, digestates have higher inorganic nitrogen contents than raw manures, which could translate into increased emissions of potent greenhouse gases such as nitrous oxide (N2O) and methane (CH4). To mitigate these emissions, the addition of biochar with high nutrient absorption capacity is suggested. To quantify the effects of anaerobic digestion and biochar amendment on N2O and CH4 emissions, we conducted a study over 33 months with four different crops (silage maize, winter wheat, winter barley, and forage grass). We measured soil parameters such as mineral nitrogen, moisture, and temperature. The N2O emissions after application of digestates were generally similar to those observed after cattle slurry or mineral fertilizer application. The highest N2O emissions were observed in the first year of the experiment during maize cultivation and were strongly influenced by high soil nitrate concentrations, which were likely linked to enhanced soil organic N mineralization after ley termination. The CH4 emissions were mostly negative. The addition of biochar to co-digested manure before application at an annual rate of 2 t ha− 1 had no effect on N2O emissions but led to short-lived CH4 peaks from organic fertilizers directly after spreading. We conclude that digestates do not promote larger N2O emissions than mineral fertilizers or cattle slurry, and that biochar addition to digestates in small application quantities does not reduce N2O emissions but bears the risk of CH4 release.

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Roman Hüppi

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