ILRI Mazingira Centre

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Defatted black soldier fly larvae meal as a substitute of soybean meal in dairy cow diets
(Journal Article, 2025-04-15) Braamhaar, D.J.M.; Pellikaan, W.F.; List, D.; Korir, Daniel; Tanga, C.M.; Oosting, S.J.
The replacement of soybean meal (SBM) with insect meal, e.g. black soldier fly larvae meal (BSFLM), as an alternative protein source in livestock feed is gaining traction globally. To date, no in vivo studies have been conducted to test the impact of BSFLM on the milk production of dairy cows. This study quantified the effects of replacing SBM with defatted black soldier fly larvae meal (DBSFLM) in diets of lactating dairy cows on feed intake, milk production and composition, apparent total-tract digestibility, feed- and nitrogen use efficiency. Twelve lactating Holstein-Friesian cows were used in a replicated 3 × 3 Latin square design (18 d per period) with 3 protein treatments: a diet containing SBM as the main protein source (control, SBM); a diet with a 50: 50 mixture of SBM and DBSFLM (SBM: DBSFLM, 50: 50); and a diet with DBSFLM (DBSFLM). Animals were blocked per Latin square based on milk yield (MY), and the amount of concentrate in the diets was adjusted for MY. Diets were provided as a total mixed ration and offered ad libitum. Our results showed no treatment effects (P > 0.05) on milk yield and composition. DM and organic matter (OM) intake were significantly higher (P ≤ 0.003) for cows fed SBM (17.6 and 16.2 kg/d, respectively) compared with DBSFLM (16.6 and 15.1 kg/d, respectively), while DM and OM intake of SBM: DBSFLM (17.5 and 16.0 kg/d, respectively) did not differ from SBM but were higher compared with DBSFLM. CP intake was significantly higher (P = 0.003) for cows fed SBM (2.68 kg/d) compared with both DBSFLM (2.50 kg/d) and SBM: DBSFLM (2.54 kg/d), while CP intake for SBM: DBSFLM did not differ from DBSFLM. Apparent total-tract digestibility of NDF and ADF were significantly lower (P ≤ 0.024) for cows fed SBM (46.7 and 45.6%, respectively) compared with DBSFLM (54.0 and 52.0%, respectively), with SBM: DBSFLM (51.0 and 49.7%, respectively) not differing from either diet. No treatment effects were observed for DM, OM, CP and ether extract digestibility, and feed and nitrogen use efficiency. Incorporating DBSFLM into dairy cow diets did not significantly compromise the milk yield and composition, suggesting its potential to reduce the reliance on SBM and contribute to circular food systems.
The Mazingira Centre analytical services laboratory
(Brochure, 2024-11-30) International Livestock Research Institute
Mazingira cost structure and laboratory analysis procedures
(Internal Document, 2024-10-30) International Livestock Research Institute
ILRI’s work on pig manure management for improving water quality in Uganda
(Presentation, 2024-08-29) Ibrahim, Wanyama; Leitner, Sonja
Toward compatibility with national dairy production and climate goals through locally appropriate mitigation interventions in Kenya
(Journal Article, 2024-10-01) Graham, Michael; Özkan, S.; Arndt, Claudia; González-Quintero, R.; Korir, Daniel; Merbold, Lutz; Mottet, A.; Ndung'u, Phyllis W.; Notenbaert, An Maria Omer; Leitner, Sonja
Greenhouse gas emissions from traditional livestock enclosures in Kenya and options for mitigation
(Presentation, 2024-09-12) Leitner, Sonja; Carbonell, V.; Yuhao Zhu; Butterbach-Bahl, Klaus; Barthel, M.; Mhindu, R.L.; Mutuo, Paul M.; Buchmann, Nina; Merbold, Lutz
Managing emissions and nutrient losses from cattle manure through cascades with carbonized materials in Kenya
(Poster, 2024-09-11) Keino, L.; Yuhao Zhu; Roobroeck, D.; Chebet, Arusey; Oduor, C.O.; Njoroge, R.; Otinga, A.; Hendre, Prasad; Leitner, Sonja
Demonstrating the potential of biochar to reduce nitrogen losses and GHG emissions from manure and improve its fertilizer quality
(Poster, 2024-08-13) Keino, L.; Yuhao Zhu; Roobroeck, D.; Chebet, A.; Oduor, Collins; Njoroge, R.; Otinga, A.; Hendre, P.; Leitner, Sonja
Greenhouse gas emissions from cattle enclosures in semi-arid sub-Saharan Africa: The case of a rangeland in South-Central Kenya
(Journal Article, 2024-06-15) Leitner, Sonja M.; Carbonell, Victoria; Mhindu, Rangarirayi L.; Zhu, Yuhao; Mutuo, Paul; Butterbach-Bahl, Klaus; Merbold, Lutz
Extensive livestock production in pastoral areas supports millions of livestock keepers in Sub-Saharan Africa (SSA). However, it is also linked to environmental externalities such as greenhouse gas (GHG) emissions. Corralling of livestock overnight in fenced enclosures (“bomas” in Kiswahili) is common to protect animals from theft and predation and is practiced across SSA. Boma manure is usually not removed and accumulates over years, making bomas GHG emission hotspots. The following study presents the first full year of CO2, CH4, and N2O emissions measurements from cattle bomas in a savanna ecosystem in Kenya, comparing active (in use) and inactive (i.e., abandoned) bomas. Active bomas were used for 1–3 months before being abandoned and cattle were moved to a new boma. GHG emissions were measured using static chambers inside three replicate bomas and along three 100 m transects from bomas into undisturbed savanna. Compared to savanna background fluxes, it was found that GHG flux rates from bomas were elevated by several orders of magnitude, with mean fluxes of 487 ± 8 mg CO2-C m−2 h−1, 325 ± 11 µg N2O-N m−2 h−1, and 3245 ± 234 µg CH4-C m−2 h−1 for active bomas, and 167 ± 52 mg CO2-C m−2 h−1, 610 ± 186 µg N2O-N m−2 h−1, and 3127 ± 1262 µg CH4-C m−2 h−1 for inactive bomas, while surrounding savanna soils only emitted 22.3 ± 18.2 mg CO2-C m−2 h−1, 2.5 ± 2.2 µg N2O-N m−2 h−1, and 0.1 ± 0.7 µg CH4-C m−2 h−1. Assuming that bomas are used for 45 days per year, annual manure emission factors were 2.43 ± 0.42%N for N2O and 0.49 ± 0.07%C for CH4, which corresponds to 2.64 ± 0.37 g CH4 kg−1 volatile solids (VS). These emission factors were similar to IPCC default values for feedlots for low-producing cattle in warm climates; however, the IPCC only considers emissions in year when bomas are in use and does not account for emissions following boma abandonment. At the farm scale, boma manure contributed little (2.2%) to total CH4 emissions, which were dominated by enteric CH4 emissions (97.6%); but bomas were a substantial source for N2O, contributing over 32% to total N2O emissions on the farm. This calls for the inclusion of active and inactive bomas in the activity data collection for national GHG inventories, as bomas are currently overlooked hotspots for GHG emissions that are not represented in the GHG budgets of African nations. To mitigate GHG emissions, manure should be removed regularly and used as fertilizer to return nutrients to the grassland, preventing nutrient mining and ensuring long-term rangeland productivity and resilience, or it might be used to grow crops and livestock feeds.
Greenhouse gas emissions from sheep excreta deposited onto tropical pastures in Kenya
(Journal Article, 2024-01) Zhu, Yuhao; Butterbach-Bahl, Klaus; Merbold, Lutz; Oduor, Collins; Gakige, Jesse K.; Mwangi, Paul; Leitner, Sonja
To improve the estimate of greenhouse gas emissions (GHG) from tropical rangelands in sub-Saharan Africa, we measured GHG emissions from sheep excreta over two periods of 51 days on a Kenya rangeland. In addition, we measured GHG emissions from potential hotspots in the landscape linked to sheep grazing: overnight enclosures (“bomas”), where sheep are kept at night to protect them from theft and predators, the areas surrounding sheep bomas, and areas surrounding watering troughs. Results showed a short pulse of CO2 fluxes after sheep urine application and a rapid increase of CH4 fluxes following sheep dung application in both rainy and dry season. However, only small increases of N2O fluxes were observed after dung and urine applications compared to controls without excreta. Elevated N2O fluxes mainly coincided with heavy rainfall. Overall, N2O emission factors (EFs) did not vary across excreta type or seasons, but mean N2O EFs for dung (0.01%) and urine patches (0.02%) were only one tenth of the default EFs from the 2019 IPCC Refinement for dry climate. We did, however, find that bomas and watering troughs are sites of herd concentration that are important sources of GHG emissions in the landscape, and that emissions in these locations can remain elevated for months to years, especially when soil moisture is high. This study contributes to more robust estimates of GHG emissions from African livestock systems, which are fundamental to develop targeted mitigation strategies.
Nitrous oxide emission factors for cattle dung and urine deposited onto tropical pastures: A review of field-based studies
(Journal Article, 2021-12) Zhu, Yuhao; Butterbach-Bahl, Klaus; Merbold, Lutz; Leitner, Sonja; Pelster, David E.
Livestock excreta on pastures is an important source of nitrous oxide (N 2 O) emissions, however studies measuring these emissions in tropical regions, particularly Africa, remain limited. Therefore we measured N 2 O emissions from different quantities of dung patches during three observation periods (dry, wet and transition from dry to wet season) and different volumes of urine patches during wet and dry seasons. Dung patches did not stimulate soil N 2 O emissions in any of the three observation periods, while urine application stimulated soil N 2 O emissions during both seasons, with higher emissions observed during the wet season. The dung EFs (0.00–0.03%) and the urine EFs (0.04–0.40%) showed no detectable effects of dung quantity or urine volume. We further synthesized observations from other studies in wet and dry tropical regions, which indicated that the excreta N 2 O EFs were similar to the default values provided in the IPCC 2019 refinement (0.11% vs 0.07% for dung and 0.41% vs 0.32% for urine in dry climates, and 0.13% vs 0.13% for dung and 0.65% vs 0.77% for urine in wet climates). However, sub-Saharan African (SSA) studies had consistently lower EFs, possibly due to the lower urine-N: dung-N ratio in SSA compared with the other tropical regions, suggesting that the refinement may still overestimate excreta emissions in SSA. Moreover, considering the large variations in the summarized tropical excreta N 2 O EFs, from -0.01 to 1.77% for dung and 0.00 to 4.90% for urine, more studies under diverse conditions across tropical regions are recommended. • Excreta N 2 O emission factors not influenced by mass or volume. • Soil type and N partitioning are overlooked factors in national N 2 O inventories. • IPCC 2019 refinement may still overestimate excreta N 2 O emissions in SSA.
Number of chamber measurement locations for accurate quantification of landscape-scale greenhouse gas fluxes: Importance of land use, seasonality, and greenhouse gas type
(Journal Article, 2022-09) Wangari, E.G.; Mwanake, R.M.; Kraus, D.; Werner, C.; Gettel, G.M.; Kiese, Ralf; Breuer, L.; Butterbach-Bahl, Klaus; Houska, T.
Accurate quantification of landscape soil greenhouse gas (GHG) exchange from chamber measurements is challenging due to the high spatial-temporal variability of fluxes, which results in large uncertainties in upscaled regional and global flux estimates. We quantified landscape-scale (6 km2 in central Germany) soil/ecosystem respiration (SR/ER-CO2), methane (CH4), and nitrous oxide (N2O) fluxes at stratified sites with contrasting landscape characteristics using the fast-box chamber technique. We assessed the influence of land use (forest, arable, and grassland), seasonality (spring, summer, and autumn), soil types, and slope on the fluxes. We also evaluated the number of chamber measurement locations required to estimate landscape fluxes within globally significant uncertainty thresholds. The GHG fluxes were strongly influenced by seasonality and land use rather than soil type and slope. The number of chamber measurement locations required for robust landscape-scale flux estimates depended on the magnitude of fluxes, which varied with season, land use, and GHG type. Significant N2O-N flux uncertainties greater than the global mean flux (0.67 kg ha−1 yr−1) occurred if landscape measurements were done at <4 and <22 chamber locations (per km2) in forest and arable ecosystems, respectively, in summer. For CO2 and CH4 fluxes, uncertainties greater than the global median CO2-C flux (7,500 kg ha−1 yr−1) and the global mean forest CH4-C uptake rate (2.81 kg ha−1 yr−1) occurred at <2 forest and <6 arable chamber locations. This finding suggests that more chamber measurement locations are required to assess landscape-scale N2O fluxes than CO2 and CH4, based on these GHG-specific uncertainty thresholds.
Impacts of land cover and management change on top-of-canopy and below-canopy temperatures in Southeastern Kenya
(Journal Article, 2023-05) Abera, T.; Heiskanen, J.; Maeda, E.; Odongo, Vincent O.; Pellikka, P.
Impacts of land cover conversion have been studied well from the top-of-canopy level using satellite observations. Yet, the warming or cooling impacts of land cover and management change (LCMC) from below-canopy level remain less explored. Here, we studied the below-canopy temperature change from field to landscape level across multiple LCMC in southeastern Kenya. To study this, in situ microclimate sensors, satellite observations, and high-resolution below-canopy temperature modelling approaches were used. Our results show that from field to landscape scale, forest to cropland conversion, followed by thicket to cropland change, generate higher surface temperature warming than other conversion types. At field scale, tree loss increases the mean soil temperature (measured at 6 cm below ground) more than the mean below-canopy surface temperature but its impact on the diurnal temperature range was higher on surface temperature than soil temperature in both forest to cropland and thicket to cropland/grassland conversions. At landscape scale, compared with top-of-canopy land surface temperature warming, which was estimated at Landsat overpass time (∼10:30 a.m.), forest to cropland conversion generates ∼3 °C higher below-canopy surface temperature warming. Land management change, through fencing of wildlife conservation areas and limiting mobility of mega browsers, can have an impact on woody cover and induce more below-canopy surface temperature warming than top-of-canopy in comparison with non-conservancy areas. These results indicate that human induced land changes can generate more below-canopy warming than inferred from top-of-canopy satellite observations. Together, the results highlight the importance of considering the climatic impacts of LCMC from both top-of-canopy and below-canopy level for effective mitigation of anthropogenic warming from land surface changes.
Less burping, more meat and milk - how livestock farmers can help tackle the climate crisis
(Blog Post, 2022-11-21) Arndt, Claudia; Hristov, Alexander N.; Dijkstra, J.
Forage quality of species-rich mountain grasslands subjected to zero, PK and NPK mineral fertilization for decades
(Journal Article, 2020-12) Ineichen, Simon; Marquardt, Svenja; Kreuzer, Michael; Reidy, Beat
To maintain species‐rich swards from which forage of a high nutritional quality can be produced, it is essential to adapt grassland fertilization strategies. In this study, we investigated how different long‐term mineral fertilization treatments affect dry‐matter (DM) yield, plant species composition, and nutrient and mineral concentrations of forage from mountain grasslands. During 2 years, forage was sampled from three different long‐term fertilization experiments located at 930 (L), 1,190 (M) and 1,340 (H) m a.s.l. at different sites in Switzerland. At each site, three mineral fertilization treatments (0, PK and NPK) had been maintained for three to six decades, with two (L and M) or three harvests (H) per year. Yield, the botanical composition and concentrations of net energy, utilizable crude protein and different phenolic fractions were determined. Nutrient and mineral concentrations were also determined. For all three sites (L, M and H), unfertilized swards had lower annual DM yields (3.39, 5.17 and 2.73 t/ha) compared to PK (6.33, 7.17 and 4.44 t/ha) and NPK fertilized swards (7.69, 7.22 and 7.44 t/ha), respectively. Long‐term fertilization had little effect on the gross nutrient and phenolic composition, but forage P and K concentration increased. The decades‐long fertilization of either PK or NPK of up to 85 kg N, 80 kg P2O5 and 240 kg K2O/ha reduced plant species richness only at site H. Fertilization of PK may allow to simultaneously increase forage productivity and maintain forage quality in mountain grasslands.
Multimodel evaluation of nitrous oxide emissions from anintensively managed grassland
(Journal Article, 2020-01) Fuchs, K.; Merbold, Lutz; Buchmann, Nina; Bretscher, D.; Brilli, L.; Fitton, N.; Topp, C.F.E.; Klumpp, K.; Lieffering, M.; Martin, R.; Newton, P.C.D.; Rees, R.M.; Rolinski, S.; Smith, P.; Snow, V.
Process‐based models are useful for assessing the impact of changing management practices and climate on yields and greenhouse gas (GHG) emissions from agricultural systems such as grasslands. They can be used to construct national GHG inventories using a Tier 3 approach. However, accurate simulations of nitrous oxide (N2O) fluxes remain challenging. Models are limited by our understanding of soil‐plant‐microbe interactions and the impact of uncertainty in measured input parameters on simulated outputs. To improve model performance, thorough evaluations against in situ measurements are needed. Experimental data of N2O emissions under two management practices (control with typical fertilization versus increased clover and no fertilization) were acquired in a Swiss field experiment. We conducted a multimodel evaluation with three commonly used biogeochemical models (DayCent in two variants, PaSim, APSIM in two variants) comparing four years of data. DayCent was the most accurate model for simulating N2O fluxes on annual timescales, while APSIM was most accurate for daily N2O fluxes. The multimodel ensemble average reduced the error in estimated annual fluxes by 41% compared to an estimate using the Intergovernmental Panel on Climate Change (IPCC)‐derived method for the Swiss agricultural GHG inventory (IPCC‐Swiss), but individual models were not systematically more accurate than IPCC‐Swiss. The model ensemble overestimated the N2O mitigation effect of the clover‐based treatment (measured: 39–45%; ensemble: 52–57%) but was more accurate than IPCC‐Swiss (IPCC‐Swiss: 72–81%). These results suggest that multimodel ensembles are valuable for estimating the impact of climate and management on N2O emissions.
Understanding N2O emissions in African ecosystems: Assessments from a semi-arid Savanna grassland in Senegal and sub-tropical agricultural fields in Kenya
(Journal Article, 2020-11-01) Bigaignon, L; Delon, C; Ndiaye, O; Galy-Lacaux, C; Serça, D; Guérin, F; Tallec, T; Merbold, Lutz; Tagesson, T; Fensholt, R; André, A; Galliau, S
This study is based on the analysis of field-measured nitrous oxide (N2O) emissions from a Sahelian semi-arid grassland site in Senegal (Dahra), tropical humid agricultural plots in Kenya (Mbita region) and simulations using a 1D model designed for semi arid ecosystems in Dahra. This study aims at improving present knowledge and inventories of N2O emissions from the African continent. N2O emissions were larger at the agricultural sites in the Mbita region (range: 0.0 ± 0.0 to 42.1 ± 10.7 ngN m−2 s−1) than at the Dahra site (range: 0.3 ± 0 to 7.4 ± 6.5 ngN m−2 s−1). Soil water and nitrate (NO3−) contents appeared to be the most important drivers of N2O emissions in Dahra at the seasonal scale in both regions. The seasonal pattern of modelled N2O emissions is well represented, though the model performed better during the rainy season than between the rainy and dry seasons. This study highlighted that the water-filled pore space threshold recognised as a trigger for N2O emissions should be reconsidered for semi-arid ecosystems. Based on both measurements and simulated results, an annual N2O budget was estimated for African savanna/grassland and agricultural land ranging between 0.17–0.26 and 1.15–1.20 TgN per year, respectively.
Inferring CO2 fertilization effect based on global monitoring land-atmosphere exchange with a theoretical model
(Journal Article, 2020-08-01) Ueyama, M.; Ichii, Kazuhito; Kobayashi, H.; Kumagai, T.; Beringer, J.; Merbold, Lutz; Euskirchen, E.; Hirano, T.; Belelli, M.L.; Baldocchi, D.; Taku, S.; Mizoguchi, Y.; Ono, K.; Joon, K.; Varlagin, Andrej; Kang, M.; Shimizu, T.; Kosugi, Y.; Bret-Harte, M.; Machimura, T.; Matsuura, Y.; Ohta, T.; Takagi, K.; Takanashi, S.; Yasuda, Y.
Rising atmospheric CO2 concentration ([CO2]) enhances photosynthesis and reduces transpiration at the leaf, ecosystem, and global scale via the CO2 fertilization effect. The CO2 fertilization effect is among the most important processes for predicting the terrestrial carbon budget and future climate, yet it has been elusive to quantify. For evaluating the CO2 fertilization effect on land photosynthesis and transpiration, we developed a technique that isolated this effect from other confounding effects, such as changes in climate, using a noisy time series of observed land-atmosphere CO2 and water vapor exchange. Here, we evaluate the magnitude of this effect from 2000 to 2014 globally based on constraint optimization of gross primary productivity (GPP) and evapotranspiration in a canopy photosynthesis model over 104 global eddy-covariance stations. We found a consistent increase of GPP (0.138 ± 0.007% ppm−1; percentile per rising ppm of [CO2]) and a concomitant decrease in transpiration (−0.073% ± 0.006% ppm−1) due to rising [CO2]. Enhanced GPP from CO2 fertilization after the baseline year 2000 is, on average, 1.2% of global GPP, 12.4 g C m−2 yr−1 or 1.8 Pg C yr−1 at the years from 2001 to 2014. Our result demonstrates that the current increase in [CO2] could potentially explain the recent land CO2 sink at the global scale.
Improving assessments of the three pillars of Climate Smart Agriculture: Current achievements and ideas for the future
(Journal Article, 2020-09-22) Wijk, Mark T. van; Merbold, Lutz; Hammond, James; Butterbach-Bahl, Klaus
In this study we evaluate Climate Smart Agriculture (CSA) assessment tools with regard to their suitability for covering not only biophysical but also socio-economic aspects of CSA, focusing on smallholder household level in Low and Middle Income Countries (LMIC). In this opinion piece we give a concise overview of the most recent developments in measuring key indicators and metrics for the three pillars of CSA (food security, adaptation and mitigation) and give our opinion on how we think this would allow for improvements in the current state of assessing CSA in a smallholder farming context. Our assessment shows that all tools reviewed here have a biophysical lens while looking at productivity, and largely ignore potential social (e.g. food security, gender) and economic (poverty) aspects of the sustainability of intensified production. Mitigation was also analyzed in all approaches but few tools go beyond greenhouse gas emissions to analyse environmental sustainability (for example water quality, soil health, ecosystem services) more generically. Climate change adaptation was the CSA pillar with the weakest representation within the approaches reviewed here. Based on an overview of recent advantages in work focusing on CSA our key recommendations are i) to make better use of recent advances in indicator development for sustainability assessments, including work on quantification of water and land footprints in relation to farm management; ii) to use household level analyses to quantify pathways from productivity towards food security and improved nutrition as well as descripting drivers of adoption of adaptation options; and iii) to use recent advances in system specific quantification of greenhouse gas emissions through both LMIC focused modelling and empirical work.
Closing maize yield gaps in sub-Saharan Africa will boost soil N2O emissions
(Journal Article, 2020-12) Leitner, Sonja; Pelster, David E.; Werner, Christian R.; Merbold, Lutz; Baggs, Elizabeth M.; Mapanda, Farai; Butterbach-Bahl, Klaus

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