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  • Manure management to improve soil structure and food security and mitigate greenhouse gas emission
    Manure management to improve soil structure and food security and mitigate greenhouse gas emission Ndambi, Asaah; Pelster, David; Butterbach-Bahl, Klaus
  • The impact of management and climate on soil nitric oxide fluxes from arable land in the Southern Ukraine
    The impact of management and climate on soil nitric oxide fluxes from arable land in the Southern Ukraine Medinets, S.; Gasche, R.; Skiba, U.; Medinets, V.; Butterbach-Bahl, Klaus NO fluxes from soils are a significant source for tropospheric NOx, though global and regional estimates of the soil source strength are constrained by the paucity of measurements. In a continuous 18 month effort (2012–2014) soil NO fluxes from an intensively managed arable site in the black soil region of the Southern Ukraine (Odessa region) were measured using an automated dynamic chamber system. Measurements revealed three periods of peak NO emissions (fertigation, re-wetting of soils, and to a lower extend during winter), with a pulse emission peak during soil re-wetting in summer of 88.4 μg N m−2 h−1. The mean annual NO flux was 5.1 ± 8.9 μg N m−2 h−1 and total annual NO emissions were 0.44 ± 0.78 kg N ha−1 yr−1. The fertilizer induced emission factor for NO was 0.63% under beetroot. The combined effect of soil temperature, soil moisture and soil DIN (NH4+ and NO3−) concentrations were identified as drivers of the temporal and spatial variability of soil NO fluxes. This work shows that long-term measurements are needed for estimating annual fluxes and the importance of soils as a source for tropospheric NOx as the contribution of different seasons and crop growing periods to the annual budget differed markedly.
  • Methane and nitrous oxide emissions from cattle excreta on an East African grassland
    Methane and nitrous oxide emissions from cattle excreta on an East African grassland Pelster, David; Gisore, B.; Goopy, J.P.; Korir, D.; Koske, J.K.; Rufino, Mariana C.; Butterbach-Bahl, Klaus Greenhouse gas (GHG) emission measurements from livestock excreta in Africa are limited. We measured CH4 and N2O emissions from excreta of six Boran (Bos indicus) and six Friesian (Bos taurus) steers near Nairobi, Kenya. The steers were fed one of three diets (T1 [chaffed wheat straw], T2 [T1 + Calliandra calothyrsus Meissner – 0.2% live weight per day], and T3 [T1 + calliandra – 0.4% live weight every 2 d]). The T1 diet is similar in quality to typical diets in the region. Calliandra is a leguminous fodder tree promoted as a feed supplement. Fresh feces and urine were applied to grasslands and emissions measured using static chambers. Cumulative 28-d fecal emissions were 302 ± 52.4 and 95 ± 13.8 mg CH4–C kg−1 dry matter for Friesen and Boran steers, respectively, and 11.5 ± 4.26 and 24.7 ± 8.32 mg N2O–N kg−1 dry matter for Friesian and Boran steers, respectively. For urine from Friesian steers, the N2O emissions were 2.8 ± 0.64 mg N2O–N 100 mL urine−1. The CH4 emission factors (EFs) (246 ± 49.5 and 87 ± 12.7 g CH4–C yr−1 animal−1 for Friesan and Boran, respectively) were lower than the International Panel on Climate Change EFs (750 g CH4–C animal−1 yr−1), whereas the N2O EFs (0.1 and 0.2% for the Friesian and Boran feces, respectively, and 1.2% for urine) were also lower than International Panel on Climate Change estimates. The low N content of the excreta likely caused the low emissions and indicates that current models probably overestimate CH4 and N2O emissions from African livestock manure.
  • Supplementation with Calliandra calothyrsus improves nitrogen retention in cattle fed low-protein diets
    Supplementation with Calliandra calothyrsus improves nitrogen retention in cattle fed low-protein diets Korir, D.; Goopy, J.P.; Gachuiri, C.; Butterbach-Bahl, Klaus; Eckard, R.; Anderson, C. Ruminant productivity in the tropical Africa has remained low despite decades of research on animal nutrition and introduction of new breeds of animals mainly because of low-quality feeds available, especially during the dry season that is inefficiently utilised. This results in prolonged time for animals to mature and increased nutrient excretion to the environment. We conducted a study using yearling steers (n = 12, liveweight (LW) = 161.8 ± 10.89 kg) in a 3 × 3 Latin square to evaluate the effect of protein supplementation and supplementation frequency on intake, digestibility, nitrogen (N) retention and microbial N supply in cattle consuming low-protein diets. The steers were maintained on ad libitumwheat straw (DM = 877 ± 5 g/kg, crude protein (CP) = 20.0 ± 1.1 g/kg), with supplemental protein supplied as air-driedCalliandra calothyrsus leaves (DM = 897 ± 3 g/kg, CP = 257.5 ± 4.1 g/kg on a DM basis). Samples of basal diet, supplement, refusals, faecal matter and urine were collected and analysed per treatment. Supplementation increased intakes by the steers (P < 0.001), with no difference between the two supplementation frequencies (P > 0.404). Steers lost bodyweight (P < 0.05) on all treatments, but less so when supplemented. Nitrogen losses was reduced (P < 0.001) with supplementation (–33.3% vs 15.7%, s.e.m. 0.06). The increased N balance in animals receiving supplemented diets indicated that N retention actually improves with increased protein supplementation in animals fed low-protein diets, implying that improving protein supply to animals fed submaintenance diets will not only ameliorate production losses, but will actually decrease non-enteric greenhouse gas production and environmental N losses per animal product unit obtained.
  • Vines of the sweet potato (Ipomea batatas): A valuable feed supplement for ruminants in small holder systems
    Vines of the sweet potato (Ipomea batatas): A valuable feed supplement for ruminants in small holder systems Goopy, J.P.; Gakige, J.; Korir, D.; Kvacic, M.; Butterbach-Bahl, Klaus Availability of suitable feed, and in particular sources of protein-rich food, is a major constraint to increasing the productivity of smallholders in sub-Saharan Africa it is difficult to justify diverting land from growing crops for human consumption. The roots of the sweet potato are a high energy cash crop, and the leaves and vines (SPV), usually treated as rubbish, are high in protein and have been identified as a valuable livestock feed.
  • Long-term assessment of soil and water conservation measures (Fanya-juu terraces) on soil organic matter in South Eastern Kenya
    Long-term assessment of soil and water conservation measures (Fanya-juu terraces) on soil organic matter in South Eastern Kenya Saiz, G.; Wandera, F.M.; Pelster, David; Ngetich, W.; Okalebo, J.R.; Rufino, Mariana C.; Butterbach-Bahl, Klaus A comprehensive assessment of soil organic matter (SOM) dynamics in semi-arid agrosystems implementing soil and water conservation (SWC) measures is still lacking despite their extent, ecological and economic significance. Therefore, we assessed the long-term impact of a commonly used SWC technique (Fanya-juu terracing) on SOM-related properties in South Eastern Kenya. A soil sampling campaign was conducted in a replicated stratified random manner on three land uses that had been continuously managed for over 30 years. Samples were analyzed for organic carbon and nitrogen contents, δ13C, δ15N, pH and texture. Compared to sites implementing conventional agriculture, the establishment of SWC structures in this erosion-prone landscape resulted in the recovery of SOM levels comparable to those observed in neighboring semi-natural ecosystems. Sites under conventional agriculture practices contained 20 Mg C ha− 1 (0.85 m), while sites with SWC measures and those hosting semi-natural vegetation stored above a third more. There were significant differences in soil C/N ratios as well as in δ13C and δ15N values between SWC cultivation practices classified according to the presence or absence of trees. The presence of woody vegetation in sites with SWC structures had a strong impact on the spatial variability of SOM-related properties. There was also a significant negative relationship between δ15N values and C/N ratios across the different land uses. Our findings indicate the existence of contrasting SOM dynamics caused by vegetation-related effects, and provide suggestions for enhancing SOM storage in agricultural sites implementing SWC measures.
  • Manure management in the (sub-)tropics; Training manual for extension workers
    Manure management in the (sub-)tropics; Training manual for extension workers Teenstra, E.; Buisonjé, F. de; Ndambi, A.; Pelster, David Having identified a general lack of knowledge about the value of livestock manure and integrated manure management at multiple levels in government and society, a concerted action led to the compilation of a training manual for extension workers on manure management in the (sub-)tropics. Covering the whole manure chain, from animal excretion to the final application, the manual describes the basic principles of integrated manure management. Although much information originates from more temperate regions, the manual focusses on farm practices in the tropics and subtropics.
  • How to target climate-smart agriculture? Concept and application of the consensus-driven decision support framework “targetCSA”
    How to target climate-smart agriculture? Concept and application of the consensus-driven decision support framework “targetCSA” Brandt, P.; Kvakić, M.; Butterbach-Bahl, Klaus; Rufino, Mariana C. Planning for agricultural adaptation and mitigation has to lean on informed decision-making processes. Stakeholder involvement, consensus building and the integration of comprehensive and reliable information represent crucial, yet challenging, pillars for successful outcomes. The spatially-explicit multi-criteria decision support framework “targetCSA” presented here aims to aid the targeting of climate-smart agriculture (CSA) at the national level. This framework integrates quantitative, spatially-explicit information such as vulnerability indicators (e.g. soil organic matter, literacy rate and market access) and proxies for CSA practices (e.g. soil fertility improvement, water harvesting and agroforestry) as well as qualitative opinions on these targeting criteria from a broad range of stakeholders. The analytic hierarchy process and a goal optimization approach are utilized to quantify collective, consensus-oriented stakeholder preferences on vulnerability indicators and CSA practices. Spatially-explicit vulnerability and CSA data are aggregated and coupled with stakeholder preferences deriving vulnerability and CSA suitability indices. Based on these indices, relevant regions with the potential to implement CSA practices are identified. “targetCSA” was exemplarily applied in Kenya exploring group-specific and overall consensus-based solutions of stakeholder opinions on vulnerability and CSA under different consensus scenarios. In this example, 32 experts from four stakeholder groups who participated in two surveys were included. The subsequent analyses not only revealed consistently regions with high CSA potential but also highlighted different high potential areas depending on the applied consensus scenario. Thus, this framework allows stakeholders to explore the consequences of scenarios that reflect opinions of the majority and minority or are based on a balance between them. “targetCSA” and the application example contribute valuable insights to the development of policy and planning tools to consensually target and implement CSA.

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