Economic value of crop residues in African smallholder agriculture

This paper contributes to our understanding of the use and management of crop residues in East African highlands and farmers' decision-making associated with this important on-farm resource. Using the data from a socio-economic and household production survey of a sample of 310 households in 15 villages in western Kenya conducted in 2011-2012, the analysis shows that the decision to allocate maize residues to organic fertilizer and the amount of such allocation among Kenyan farmers is in uenced by the quantity of maize residues produced, as well as conventional inputs into production such as labor and chemical fertilizer. However, such allocation decisions may be independent of other competing uses of residues { livestock feed and cooking fuel. The value of maize residues as an input into crop production is also estimated

Reconciling Food, Energy, And Environmental Outcomes: Three Essays On The Economics Of Biomass Management In Western Kenya

This dissertation explores human-environment interactions, focusing on on-farm biological resources (biomass) and crop residues, in particular, and how they can meet the competing demands of food production, energy generation, and environmental conservation in SubSaharan Africa. The empirical setting is rural western Kenya, where maize residues, one of the largest sources of on-farm biomass, constitute a large portion of livestock diets, contribute to household energy needs, and are fundamental in maintaining and improving soil fertility. The three dissertation essays analyze the uses and value of crop residues in tropical smallholder agriculture from several di↵erent perspectives and using di↵erent methodological approaches, all based on data from the western Kenyan highlands. The first essay (Chapter 2) treats non-marketed crop residues as factors of household production, accounting for their long-term benefits when used for soil fertility management. Empirically, the essay estimates a household-level maize production function and calculates the shadow value of maize residues as suggested by the theoretical framework and empirical estimates. This estimated value is substantial-$0.06-08 per kilogram and$208 per average farm-and is higher for poorer households. The second essay (Chapter 3) analyzes crop residue use in an intertemporal setting and develops a dynamic bioeconomic model of agricultural households. The model combines an econometrically estimated production function and a calibrated soil carbon flow equation in a maximum principle framework to determine the optimal application rates of mineral fertilizer and crop residues. The results yield an estimated equilibrium value of soil carbon in the research area-$138 per metric ton-and highlight the significant local private benefits of soil carbon sequestration, and the potential to simultaneously increase food production and sequester carbon. Finally, the third essay (Chapter 4) considers one of the primary challenges in small-scale second-generation biofuel development-the provision of feedstocks. The essay estimates the potential availability and cost of purchasing maize residues from smallholder farmers and transporting them to a hypothetical small-scale pyrolysis-biochar plant in western Kenya. Feedstock provision costs depend on regionally specific agro-ecological and socio-economic conditions, with implications for economic viability in Kenya and, by extension, other rural settings

Local Standards, Behavioral Adjustments, and Welfare: Evaluating California\u27s Ocean-Going Vessel Fuel Rule

We examine how behavioral adjustments by regulated vessels affect welfare outcomes of a local fuel sulfur standard targeting particulate matter pollution from maritime transport. Our analysis combines one-minute scale data of vessel locations with location-specific marginal damages to obtain voyage-level measures of welfare outcomes. Exploiting the introduction of California\u27s Ocean-Going Vessel Fuel Rule, we find sharp reductions in fuel consumption in the regulated area and a considerable emission spillover in unregulated waters. Despite these adjustments, the rule generates net benefits of close to $1 billion over 29 months because the emission spillovers occur in low marginal damage areas

Agricultural productivity and soil carbon dynamics: a bio-economic model

The strong link between poverty, natural resources and the environment is apparent in smallholder agriculture: farmers are making repeated land use and management decisions while facing diverse resource endowments and significant environmental constraints on production. To investigate the likely effects of changes in agricultural practices on the natural resource base and on farmer welfare, we develop a bio-economic dynamic model of agricultural households in the western Kenya highlands. Our modeling framework extends economic farm household models to incorporate the dynamic nature of natural resource management and its implications for household welfare, and to permit a meaningful interface with biophysical processes through soil carbon management. Using an eight-year panel data set, the model combines econometrically estimated production and soil carbon flow equations in a dynamic programming framework. We use the model to determine the optimal management of the farming system over time in terms of the quantity of mineral fertilizer and crop residues to apply, taking into consideration initial resource endowments and prices. Understanding how soil resources respond to the combined applications of mineral and organic resources is important for improved resource allocation at the farm level and for national agricultural policy decisions

Perceived, measured, and estimated soil fertility in east Africa: Implications for farmers and researchers

Bringing together emerging lessons from biophysical and social sciences as well as newly available data, we take stock of what can be learned about the relationship among perceived soil fertility, measured soil fertility, and farmer management practices in east Africa. We identify the correlates of Kenyan and Tanzanian maize farmers’ reported perceptions of soil fertility and assess the extent to which these subjective assessments reflect measured soil chemistry. Our results offer evidence that farmers base their perceptions of soil quality and soil type on crop yields. We also find that, in Kenya, farmers’ reported soil type is a reasonable predictor of several objective soil fertility indicators while farmer-reported soil quality is not. In addition, in exploring the extent to which publicly available soil data are adequate to capture local soil chemistry realities, we find that there is still immense value to the time-consuming collection of soil samples where highly accurate soil measures are important to research objectives. However, in the estimation of agricultural production or profit functions, where the focus is on averages and where there is low variability in the soil properties, there may be limited value to including any soil information in the analysis

Fuelwood Source Substitution and Shadow Prices in Western Kenya

Deforestation in Sub-Saharan Africa remains a substantial problem. Increasing scarcity of fuelwood can be significant burden to households, as fuelwood is a key component of the energy profile of a rural Sub-Saharan household. However, households do not only collect their fuelwood from off-farm, but also produce it on-farm and purchase it from the market. This paper studies substitution between fuelwood sources for rural Kenyan households. Conducting analysis using shadow prices for household fuelwood in a non-separable theoretical framework, we find that strict gender divisions in household labor contribute to a lack of substitution between fuelwood sources. Because fuelwood production on the farm is more sustainable than off-farm collection, gender divisions inhibit reforestation efforts in this area. This paper finds a direct linkage between women and environmental well-being, and concludes that reforestation efforts in SSA will likely be ineffective until labor substitution between genders increase

Paying for agricultural information in Malawi: the role of soil heterogeneity

We examine the relationship between soil heterogeneity and investment in learning among farmers in Central Malawi using an experimental approach. Soil heterogeneity may both impede social learning and encourage experimentation. In our experiment, farmers contribute towards the purchase of a single soil test in the village in a threshold public goods game. This soil tests provides farmers with valuable and actionable information. By randomly varying the plot selected for soil testing we establish the role of soil heterogeneity. We find that farmers contribute more when they perceive soils to be more similar to their own plot, but also free ride on others whose soils they perceive as similar. This free riding increases in larger groups of farmers with similar soils. Despite this, all villages consistently contribute enough to purchase the soil test.</p