Anthony A. Kimaro

Greenhouse gas fluxes from agricultural soils of Kenya and Tanzania

Knowledge of greenhouse gas (GHG) fluxes in soils is a prerequisite to constrain national, continental, and global GHG budgets. However, data characterizing fluxes from agricultural soils of Africa are markedly limited. We measured carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) fluxes at 10 farmer-managed sites of six crop types for 1 year in Kenya and Tanzania using static chambers and gas chromatography. Cumulative emissions ranged between 3.5–15.9 Mg CO2-C ha−1 yr−1, 0.4–3.9 kg N2O-N ha−1 yr−1, and −1.2–10.1 kg CH4-C ha−1 yr−1, depending on crop type, environmental conditions, and management. Manure inputs increased CO2 (p = 0.03), but not N2O or CH4, emissions. Soil cultivation had no discernable effect on emissions of any of the three gases. Fluxes of CO2 and N2O were 54–208% greater (p < 0.05) during the wet versus the dry seasons for some, but not all, crop types. The heterogeneity and seasonality of fluxes suggest that the available data describing soil fluxes in Africa, based on measurements of limited duration of only a few crop types and agroecological zones, are inadequate to use as a basis for estimating the impact of agricultural soils on GHG budgets. A targeted effort to understand the magnitude and mechanisms underlying African agricultural soil fluxes is necessary to accurately estimate the influence of this source on the global climate system and for determining mitigation strategies.

Expert-based ex-ante assessments of potential social, ecological, and economic impacts of upgrading strategies for improving food security in rural Tanzania using the ScalA-FS approach

Subsistence farmers in sub-Saharan Africa are highly vulnerable to food insecurity given their low adaptive capacity against ecological and socio-economic shocks. Therefore, food security is one of their main challenges. Participatory action research across food value chains (FVCs) can help stabilize and enhance food security by developing upgrading strategies (UPS) that enhance specific aspects of crop production, post-harvest processing, marketing, income generation, and consumption. However, prior to their widespread adoption or upscaling, UPS need holistic understandings of their potential social, ecological, economic, and institutional challenges and opportunities in target areas. This article reports the application of the “ScalA-FS” tool, which assessed the potential success of selected UPS using assessment criteria developed by agricultural scientists and local farmers in a participatory process in Tanzania. This work is embedded in a larger participatory research project conducted in semi-arid and sub-humid ecological settings of the Dodoma and Morogoro regions of Tanzania. Results from the assessment of the potential impact of the UPS differed strongly between the UPS and the social, economic and environmental assessment criteria, but only slightly between semi-arid and sub-humid regions. The positive impacts of food-securing UPS centre on productivity and income generation. Rain water harvesting, fertilizer micro-dosing, optimized weeding, and promotion of kitchen gardens were expected to have the highest impacts after implementation. The ScalA-FS ex-ante assessments provide a knowledge base about potential impacts, as well as the potential bottlenecks to address during the implementation of UPS.

Allanblackia, butterflies and cardamom: sustaining livelihoods alongside biodiversity conservation on the forest–agroforestry interface in the East Usambara Mountains, Tanzania

Win–win outcomes for biodiversity conservation and poverty reduction are the holy grail of integrating conservation and development and are rarely met. Domestication of valued local species and introduction of high valued crops can help prevent depletion of wild resources. We compared three commodities from the forest–agroforestry interface of the East Usambara Mountains in Tanzania at different stages of domestication: (a) Allanblackia stuhlmannii, a local tree with valuable edible kernel oil; (b) butterflies, with an international market chain for pupae sold to butterfly gardens and (c) cardamom (Elettaria cardamomum), an introduced shade tolerant spice from India with established global markets. Data on production systems, institutional set-up and profitability were collected through focus group discussions, interviews with key individual informants and literature review. Cardamom has become a major support for rural livelihoods, generating 9 million USD for 750 tons of product in the area, or 850 USD per year for 10,600 households. Allanblackia and butterflies generate only 1% of that income for the landscape. For Allanblackia (around 20 USD per year for 5000 households), the transition from a forest product collected from the wild to being an agroforestry commodity is in an early but critical stage, where the slow growth of the trees and inadequate research attention to production systems, as well as modest farm gate price, currently limit farmer interest but are the focus of ongoing research. Butterflies (approximately 200 USD per year for 350 households) have had the fastest domestication pathway, with continuous innovation into new products and use, linked to international markets. There is gender-sensitive integration with household tasks and compatibility with homegarden agroforestry systems, while due attention is given to institutional arrangements of its local business scheme. Cardamoms economic success has made it a ‘villain’ to forests conservation, as forest transformation to cardamom agroforestry retains only half of the forest trees, and is a step towards further change. Differences in institutional settings of these three domestication pathways relate to their potential to reconcile biodiversity and livelihood concerns and suggest that a socio-ecological system approach to domestication is a prerequisite for a biological–technical one to achieve societal goals.

Simulated willingness of farmers to adopt fertilizer micro-dosing and rainwater harvesting technologies in semi-arid and sub-humid farming systems in Tanzania

Productivity of African agriculture falls below the global average due mainly to limited use of productivity-enhancing technologies. In Tanzania, smallholders farm without fertilizer on fragile soils in rain-fed areas. Inadequate soil nutrients, nutrient mining, and soil-moisture stress are the main factors limiting crop productivity. Fertilizer micro-dosing (MD) and rainwater harvesting (RWH) through tied ridges appear to be appropriate technologies to help replenish soil nutrients and improve soil moisture for increased crop production. It nonetheless remains unclear whether these technologies can be adopted by smallholder farmers in Tanzania. There have been limited efforts to predict adoption and diffusion of new technologies in Tanzanian agriculture. This paper assesses the willingness of farmers to adopt fertilizer MD with and without tied ridges. Data were obtained from a household baseline study, participatory ex-ante impact assessments, and simulation exercises. Our cross-section analysis used integrated ex-ante assessment tools to understand sustainability and to prioritize and sequence technology adoption and diffusion. Simulation predicted the ex-ante impact of selected technologies, the adoption rate peaks, the likelihood for reaching peaks, and the possible time required to reach peak adoption. Our findings suggest the best paths that technology users should take, while considering factors which affect adoption during research planning, implementation, and testing of the farm level technologies.

Accounting for correlation among environmental covariates improves delineation of extrapolation suitability index for agronomic technological packages

Abstract This paper generates an extrapolation suitability index (ESI) to guide scaling-out of improved maize varieties and inorganic fertilizers. The best-bet technology packages were selected based on yield gap data from trial sites in Tanzania. A modified extrapolation detection algorithm was used to generate maps on two types of dissimilarities between environmental conditions at the reference sites and the outlying projection domain. The two dissimilarity maps were intersected to generate ESI. Accounting for correlation structure among covariates improved estimate of risk of extrapolating technologies. The covariate that highly limited the suitability of specific technology package in each pixel was identified. The impact based spatial targeting index (IBSTI) identified zones that should be prioritized to maximize the potential impacts of scaling-out technology packages. The proposed indices will guide extension agencies in targeting technology packages to suitable environments with high potential impact to increase probability of adoption and reduce risk of failure.