Selecting among alternative production functions, effect of lime cost on optimal nitrogen levels and vertical integration in the West African cotton sector

Scope and Method of Study:This dissertation consists of three essays: The first essay determines the optimal level of N fertilizer for rye-ryegrass pasture using yield functions estimated with different functional forms that assume parameters are either nonstochastic or stochastic. Three yield functions were estimated: linear response plateau, quadratic, and Spillman-Mitscherlich.The second paper determines the effect of considering the cost of lime on recommendations about optimal levels of N. Yield response and soil pH change functions were estimated and used to determine the optimal levels of N and lime. The study also developed a new version of a linear response plateau function that allows the yield plateau to vary by year with respect to nitrogen but not soil pH.The third paper provides an economic explanation of the existence of parastatal vertical integration market structures in the cotton sector of West Africa, and contrasts it with other market structure alternatives in terms of welfare and sector efficiency.Findings and Conclusions:In the first essay, nonstochastic models are rejected in favor of stochastic parameter models. The stochastic models lead to smaller recommended levels of N, but the economic benefits of using fully stochastic models are small since expected profit functions are relatively flat for the stochastic models.In the second essay, considering the cost of lime reduced the optimal level of N by as much as 11.3%. Acidification potential due to N fertilizer increased nonlinearly as N rate increased. N acidification appears to be more severe with N application rates above consumptive potential of the crop than with N that is used by the plant.In the third essay, due to credit and or factor market constraints, vertical integrated cotton parastatals increase sector welfare and efficiency by supplying inputs to overcome credit constraints. Surplus sharing between the grower and the integrator is significantly shifted towards the cotton company. Removing the integrated cotton parastatals in favor of a free market structures would result in little cotton being produced

The Law of the Minimum and Sources of Nonzero Skewness for Crop Yield Distributions

Crop yields are not commonly found to be normally distributed, but the cause of the non-normal distribution is unclear. The non-normality might be due to weather variables and/or an underlying von Liebig law of the minimum (LoM) production function. Our objective is to determine the degree to which an underlying linear response stochastic plateau production function can explain the skewness of Oklahoma wheat yields at varied nitrogen rates. We use farm-level wheat data from a long-term experiment in Oklahoma, which is a unique data set to the literature. The Tembo et al. (2008) production function provides negative skewness at all levels of nitrogen with skewness near zero for both very high and very low levels of nitrogen. Observed skewness for wheat yields, however, is positive. The variation in the plateau by year shows positive skewness. Skewness in yield potential related to weather should be considered as a possible explanation of skewness.linear plateau model, non-normal distributions, skewness, wheat, yield distribution, Production Economics, Risk and Uncertainty, Q10,

Cost of coexistence between BT Maize and Open Pollinated Maze varieties in Lowland Coastal Kenya

The purpose of this study was to assess the spatial distribution of open pollinated maize varieties (OPVs) in lowland coastal Kenya and analyze how this distribution affects the economic and practical feasibility of the implementation of coexistence measures between Bt maize and OPVs. The study used both primary and secondary data. Primary data was spatially generated by a hand held GPS and farmer surveys in lowland coastal Kenya. This data was analyzed using GIS arc view software and the least squares mean procedure. Agroecological zones were used as the reference spatial strata. Secondary data was a review of the existing coexistence studies and economic performance of Bt maize. This information is analyzed and used to determine the economic and practical impacts of the different coexistence measures in lowland coastal Kenya. The findings showed that local maize varieties are popular in the region, most of it grown in zone Cl3 along the coast. However, hybrid and improved varieties are equally popular in Cl4 and Cl5. The size of maize fields didn't differ significantly between zones. The estimated mean size of maize fields across the region was 1.7hec. The distribution of the distances between maize fields was skewed to the right with an estimated mean size of 129.2m across the region. Consistent with Ingram (2000) separation distance recommendations, we found that at separation distance of 100m, 150m and 200m, approximately 48%, 52% and 53%, respectively, of the farmers would not meet the minimum isolation distance requirement. Consistent with Ingram (2000) separation distance recommendations, we found that at separation distance of 100m, 150m and 200m, approximately 48%, 52% and 53%, respectively, of the farmers would not meet the minimum isolation distance requirement. These benefits are partially offset by reduction of GM maize fields to allow for spatial separation. On average across the region, the cost of separation was found to be approximately USD21.2/hec and USD72.1/hec if the minimum separation distance is 150m and 200m respectively. At separation distances of 150m and 200m, the costs of separation represented 27.2% and 92.4%, respectively, of the gross benefits.Department of Agricultural Economic

Effect of Nitrogen Fertilization and Liming on Rye-Ryegrass Yield and Soil pH Dynamics

Using ammonium based nitrogen fertilizers in crop production has been shown to acidify soils. Lime used to correct soil pH is an important cost to producers. Recommendations of the optimal level of nitrogen to apply typically ignore the cost of lime created by nitrogen fertilization. This study was aimed to estimate soil pH change in response to nitrogen and lime application, and determine the effect of considering the cost of lime on recommendations about the optimal level of nitrogen. Yield response and pH functions were estimated and used to determine optimal levels of inputs. The effect of the cost of lime on recommendations about the optimal level of nitrogen was found to be marginal. Nitrogen acidification was found to be more severe with nitrogen application amounts above recommended rates than with nitrogen that is used by the plant.Lime, Nitrogen, Soil pH, Rye-ryegrass, Crop Production/Industries, Production Economics,

The Cost of Coexistence between Bt Maize and Open Pollinated Maize Varieties in Lowland Coastal Kenya

Kenya is currently in the process of introducing genetically modified maize (Bt maize). A major concern is that the Bt gene might cross into local varieties through cross pollination. Current regulatory strategies to ensure coexistence of the two cropping systems at the farm level rely on spatial isolation measures-separation distances and/or buffer zones. However, the interaction of practical measures and costs of spatial isolation with the farmer’s economic incentive to plant a Bt maize crop have not been studied in Kenya. The purpose of this study was to analyze the technical and economic feasibility of the implementation of spatial coexistence measures. Using spatial geo-referenced data from the actual agricultural landscape in lowland coastal Kenya, the study finds that flexible separation distances hold the possibility of ensuring coexistence in the region, but will be difficult to implement. Rigid buffer strips on the other hand are not consistent with the producers’ economic incentive to plant a Bt maize crop.Coexistence, Regulatory, Spatial, Agro-ecological zone, GM crops, Resource /Energy Economics and Policy,

Determining Optimal Levels of Nitrogen Fertilizer Using Random Parameter Models

The parameters of yield response functions can vary by year. Past studies usually assume yield functions are nstochastic ‘‘limited’’ stochastic. In this study, we estimate rye– ryegrass yield functions in which all parameters are random. The three functional forms considered are the linear response plateau, the quadratic, and the Spillman-Mitscherlich. Nonstochastic yield models are rejected in favor of stochastic parameter models. Quadratic functional forms fit the data poorly. Optimal nitrogen application recommendations are calculated for the linear response plateau and Spillman-Mitscherlich. The stochastic models lead to smaller recommended levels of nitrogen, but the economic benefits of using fully stochastic crop yield functions are small because expected profit functions are relatively flat for the stochastic yield functions. Stochastic crop yield functions provide a way of incorporating production, uncertainty into input decisions.cereal rye–ryegrass, Monte Carlo, nitrogen, random parameters, stochastic plateau, Production Economics, Q10, C12, D24,

Determining Optimal Levels of Nitrogen Fertilizer Using Random Parameter Models

The parameters of yield response functions can vary by year. Past studies usually assume yield functions are nonstochastic or ‘limited’ stochastic. In this study, we estimate rye-ryegrass yield functions where all parameters are random. Optimal nitrogen rates are calculated for two yield response functions: linear response plateau and quadratic. Nonstochastic models are rejected in favor of stochastic parameter models. However, the economic benefits of using fully stochastic models are small since optimal nitrogen rates do not differ greatly between stochastic and nonstochastic models.Linear response plateau, Monte Carlo, nitrogen, random parameters, Agricultural and Food Policy, Crop Production/Industries, Farm Management, Production Economics,

The Cost of Coexistence between Bt Maize and Open-Pollinated Maize Varieties in Lowland Coastal Kenya

Although the commercial use of agricultural biotechnology in Africa is significantly lower than in most other parts of the world, several African countries have made significant strides towards introducing GM crops. Kenya has been one of the more progressive African countries, particularly in maize, where testing and development of Bt maize has been ongoing since 1999. As part of the introduction process, biosafety protocols are being developed. The protocols require adequate measures to ensure the coexistence between GM and conventional maize varieties, minimize risks of cross contamination, and preserve the biodiversity of traditional maize varieties. Establishing coexistence between GM and conventional maize imposes additional costs on potential adopters of GM maize, especially in Kenya, where adoption will take place within highly populated smallholder farming communities. This article estimates the costs of establishing coexistence between GM and conventional maize in Kenya's coastal lowlands

Better Together: Improving Food Security and Nutrition by Linking Market and Food Systems

Market-based approaches to food security often increase agricultural productivity and income yet sometimes fail to enhance nutrition. When food security programming combines market and food systems with a specific focus on women and girls, economic and nutrition outcomes benefit. We identify distinctive and shared elements from market and food systems and highlight how they enhance nutrition outcomes when they are combined. We describe food security programming by CARE and World Vision in Bangladesh, Ethiopia, Madagascar, Zambia, and Zimbabwe, demonstrating nutrition gains in food insecure households

Mapping the risk of Rift Valley fever in Uganda using national seroprevalence data from cattle, sheep and goats

Uganda has had repeated outbreaks of Rift Valley fever (RVF) since March 2016 when human and livestock cases were reported in Kabale after a long interval. The disease has a complex and poorly described transmission patterns which involves several mosquito vectors and mammalian hosts (including humans). We conducted a national serosurvey in livestock to determine RVF virus (RVFV) seroprevalence, risk factors, and to develop a risk map that could be used to guide risk-based surveillance and control measures. A total of 3,253 animals from 175 herds were sampled. Serum samples collected were screened at the National Animal Disease Diagnostics and Epidemiology Centre (NADDEC) using a competition multispecies anti-RVF IgG ELISA kit. Data obtained were analyzed using a Bayesian model that utilizes integrated nested Laplace approximation (INLA) and stochastic partial differential equation (SPDE) approaches to estimate posterior distributions of model parameters, and account for spatial autocorrelation. Variables considered included animal level factors (age, sex, species) and multiple environmental data including meteorological factors, soil types, and altitude. A risk map was generated by projecting fitted (mean) values, from a final model that had environmental factors onto a spatial grid that covered the entire domain. The overall RVFV seroprevalence was 11.3% (95% confidence interval: 10.2–12.3%). Higher RVFV seroprevalences were observed in older animals compared to the young, and cattle compared to sheep and goats. RVFV seroprevalence was also higher in areas that had (i) lower precipitation seasonality, (ii) haplic planosols, and (iii) lower cattle density. The risk map generated demonstrated that RVF virus was endemic in several regions including those that have not reported clinical outbreaks in the northeastern part of the country. This work has improved our understanding on spatial distribution of RVFV risk in the country as well as the expected burden of the disease in livestock