Abstracts of Award-Winning Theses

This thesis determines the tradeoff between producer welfare and the provision of environmental benefits, through reduced soil erosion and fertilizer applications, on agricultural working land. A land-use allocation model of two Iowa counties is formulated as a mathematical programming problem, building upon the Takayama and Judge framework. Slope is used to reflect terrain heterogeneity, such that the spatial allocation of land-use practices impacts economic and environmental outcomes via a yield damage function and differentiated rates of soil erosion. The model differs from prior empirical models in that it includes both crop and livestock production, which gives the model the flexibility to choose whether the two activities are optimally nonseparable.
Price policy analysis indicates that the land use allocation is relatively insensitive to changes in commodity prices, i.e., altering commodity-based support payments is insufficient to attain environmental improvements. Several "green" policy instruments are simulated to estimate the cost to producers of reducing environmental damages. Limiting soil erosion with either a regulatory standard or a per unit tax reduces the average return to land by 10%. Shifting current income support payments into a system of payments for conservation land management practices, similar in essence to the Conservation Security Program, cannot attain the same soil erosion reduction with less cost to producers. Overall, the inelastic response of land use practices to commodity prices indicates that targeting the use of productive inputs, as opposed to commodity outputs, may be a more efficient means of attaining environmental improvements.     

Implications of alternative environmental policies on phosphorus loading from poultry litter

Degraded groundwater, impaired swimming, fishing, algae and weed problem are often associated with eutrophication from phosphorus (P) loadings in surface and groundwater. The concentrated growth of poultry industry and over application of litter on pasture lands may lead to excessive nutrient loadings in surface and groundwater. The Cooperative Extension Service recommendation suggests that no poultry litter should be applied if the soil test P exceeds 300 pounds per acre, irrespective of the marginal costs and benefits associated with one more unit of litter application on that piece of land. The objective of this paper is to model the economics of P loadings from poultry litter and analyze the policy implications of Cooperative Extension Service's recommendation on quantity restriction on litter applications with empirical evidence. The results indicate that there exists significant difference in the marginal values of soil between different soil series, indicating that the permit system can achieve the target at a lesser cost. In particular, the society as a whole can gain $2.7 per acre by allocating the litter to soil series 16 instead of soil series 20, provided that the contribution towards groundwater contamination from these two acres are the same.     

Comparison of Costs of Wheat Production in Saskatchewan and the U.S. Northern Plains

This paper compares I989 average variable costs for U.S. northern plains and Saskatchewan spring wheat producers. Producers are divided into three cost groups. There are more statistically significant differences between cost groups within a country than between the two countries. Relative to other producers within the same country, low-cost producers in both countries had higher yields per bushel, most bud lower variable inputs both per acre and per bushel, and most had lower debt loads. In terms of intercountry comparisons, low-cost producers in Saskatchewan and the U.S. northern plains had nearly identical average variable cash costs. While mid- and high-cost Saskatchewan producers had significantly lower average variable cash costs, they were almost entirely offset by higher fixed costs.     

Estimating the joint effect of multiple soil conservation practices: A case study of smallholder farmers in the Lake Naivasha basin,Kenya

The current study seeks to assess the private benefits associated with multiple soil conservation practices (MSCPs) by estimating the marginal value of crop production that can be attributed to such practices. In areas where land degradation associated with soil erosion causes serious agri-environmental challenges such as loss of soil fertility, siltation and eutrophication, a multiple approach to soil conservation is neccessary. However, notwithstanding efforts to encourage adoption of such practices, their uptake remains generally low. Analysing the effect of MSCPs on crop productivity is one of the ways through which the incentives for soil conservation can be explored. To achieve the stated objective, the current study applied propensity score matching and exogenous switching regression techniques to cross-sectional data collected from a random sample of farm households located in Lake Naivasha basin, Kenya. Results indicate that there is a significant positive effect of implementing multiple soil conservation practices on crop productivity. However, we note that whether the additional benefits will cover the opportunity costs associated with the implementation of these practices will depend on farm specific attributes such as slope and the soil conservation effort. In cases where marginal benefits are not substantial to cover opportunity costs for implementation of soil conservation practices, intrinsic or external incentives could be necessary. Policy interventions could focus on offering technical assistance to farmers in selecting soil conservation practices that are best suited to their local condition.     

福州市饮用水源保护区水土流失风险评价

选择植被覆盖度、地形坡度和土地利用类型来进行水土流失的风险度评价;试验区域为福州市第二饮用水源地山仔库区和塘坂库区;利用Landsat-7ETM 的影像,在计算归一化差分植被指数NDVI的基础上估算水源地保护区的植被覆盖度;利用栅格数字高程模型DEM,计算地表坡度;利用土地利用类型图获取保护区各地土地利用类型的分布;根据水利部部颁标准,对植被覆盖度、坡度和土地利用类型进行分级,建立水土流失风险评价模型,并在ArcGIS 9.0软件支持下,对上述各因子进行叠加分析,得到保护区水土流失评价风险评价;结果表明研究区内生态环境总体保护较好,但存在一定的水土流失现象,生态环境保护还需进一步加强.     

The impact of decoupled payments on U.S. cropland values

An extensive literature has shown that various farm programs may influence the value of farmland, but other studies have not examined the cropland price effects of direct, or decoupled, payments separate from countercyclical payments. This study uses nationally representative confidential field‐level panel data with farmer‐reported per‐acre land values. We analyze the impact of decoupled and other farm program payments on farmland values. Using a fixed effects model and controlling for various factors that influence farmland values, we find that an additional dollar of decoupled payments has a large and statistically significant impact on farmland values of about $18 per acre. These results are comparable with similar studies undertaken in Europe.     

Economic Impacts of Technology,Population Growth And Soil Erosion At Watershed Level: The Case Of the Ginchi in Ethiopia

A dynamic bio‐economic model is used to show that, without technological and policy intervention, soil loss levels, income and nutrition could not be substantially or sustainably improved in a highland area of Ethiopia. Although cash incomes could rise by more than 40% over a twelve‐year planning period, average per ha soil losses could be as high as 31 tonnes per ha. With the adoption of an integrated package of new technologies, however, results show the possibility of an average two‐and‐a‐half‐fold increase in cash incomes and a 28% decline in aggregate erosion levels even with a population growth rate of 2.3%. Moreover, a minimum daily calorie intake of 2000 per adult equivalent could be met from on‐farm production with no significant increases in erosion. However, higher rates of growth in nutritional requirements and population introduce significant strains on the watershed system. From a policy perspective, there is a need for a more secure land tenure policy than currently prevailing to facilitate uptake of the new technology package, and a shift from the current livestock management strategy to one that encourages livestock keeping as a commercial enterprise. It would also imply a shift to a more site‐specific approach to land management.     

U.S. Agriculture's Role in a Greenhouse Gas Emission Mitigation World: An Economic Perspective

International agreements are likely to stimulate greenhouse gas mitigation efforts. Agriculture can participate either as a source of emission reductions or as a sink for gas emission storage. Emission trading markets are likely to emerge where agriculture could sell emission offsets. Several agricultural opportunities are available at a cost of $10-25 per ton carbon dioxide. Abatement costs for non-agricultural industries have been estimated to be as much as $200-250 per ton carbon dioxide. In the longer run, agriculture's role may diminish because many agricultural strategies offer only one-time gains and non-agricultural emitters may lower costs through technical change.     

On-site economic evaluation of soil conservation practices in Honduras

Factors affecting the cost to the farmer of employing soil erosion reduction strategics are examined for the steep hillsides near Tegucigalpa, Honduras. Linear programming and MOTAD are used to examine these factors. Results indicate that some modest reductions in erosion can be achieved at little cost to the farmer by reorganizing production, switching rotations, and using contour plowing. These modest reductions still lead to extremely high rates of erosion. Sharper reductions may be achieved at progressively higher costs as erosion control structures are constructed and acreage is left fallow. There is a high cost to the farmer of reducing erosion to ‘sustainable’ levels. A consistent tradeoff emerges between levels of soil conservation, income, and risk; erosion reduction efforts lead to lower incomes and higher risk. The analysis of likely benefits to farmers for erosion reduction shows that even under assumptions of very high yield losses from soil erosion, optimal farm plans still lead to high rates of soil loss, implying a need for policies that internalize externalities if off-farm damages are to be minimized.     

Regional erosion risk mapping for decision support: A case study from West Africa

Effective soil and water management strategies require regional-scale assessment of erosion risk in order to locate prioritized area of intervention. Our study focuses on the Atacora mountain and surrounding areas (covering more than 18% of the total land area of Republic of Benin) which face a serious erosion threat despite their ecological and economic importance. To appraise the level of soil erosion risk of large area, we rely on the Instituto Nacional para la Conservación de la Naturaleza (ICONA) erosion model and use data from geographic information system (GIS). The erosion risk model requires four main inputs, namely, information on slope, lithofacies, land use and vegetation cover. The slope layer computed from ASTER digital elevation model (DEM) and the lithofacies layer inferred from digital pedogeological map are combined to draw soil erodibility map. To build soil protection map, we use land use/land cover layer extracted from LANDSAT 7 ETM + images in addition to vegetation cover layer derived from MODIS NDVI product. The final erosion risk map (with a resolution of 1 arc second) is obtained by overlapping erodibility and soil protection maps. We find that 21.8%, 58.5%, and 19.5% of the study area presents very low to low, medium, and high to very high level of erosion risk, respectively. Moreover, our findings are aggregated at the district-level (administrative unit). We observe that erosion risk is more acute in Boukoumbe district. Kerou, Kobli and Natitingou districts are mildly affected by erosion risk, while Kouande, Materi, Pehunco, Tanguieta and Toucountouna districts face a low risk. Ultimately, the proposed erosion risk map can help researchers and decision makers design and implement effective soil and water management interventions in the study area.     

ECONOMIC RELATIONSHIPS IN MILK PRODUCTION

The paper reports on the statistical aspects of work done on the National Investigation into the Economics of Milk Production in 1965/66. It argues that conclusions draw from the tabulated results of random samples invariably need checking by more rigorous methods. The method of step-wise regression with the introduction of zero-one variables is the principal technique for examining feed input/output relationships and their reflection in economic terms. Five basic dependent variables are considered: yield per cow, stocking density, output per forage acre, utilised starch equivalent per forage acre and margin over feed cost per forage acre. The discussion of the results argues the overwhelming importance of stocking rate in the profitability of milk production and that on many farms concentrates are being used at uneconomic levels. The latter part of the paper considers variation in labour productivity and argues the existence of economies of scale in the use of labour regardless of the system of herd operation.     

四川省土壤侵蚀空间分布规律研究

为了摸清四川省土壤侵蚀空间分布情况,依据全国土壤侵蚀分级系统、强度划分体系,利用GIS分析方法对全省土壤侵蚀类型与强度进行了分析。研究结果表明:①土壤侵蚀类型分水蚀、冻融侵蚀和风蚀三类,但侵蚀类型的空间差异明显,水蚀严重区位于川东,冻融侵蚀作用影响区为川西,风蚀影响区为川北一带;②水力侵蚀为土壤侵蚀最主要的类型,影响面积占总面积的87.7%,冻融次之,风蚀影响面积最小;③侵蚀强度分析显示水力侵蚀强度最大,风蚀强度次之,冻融侵蚀对土壤的破坏程度最小;④土壤侵蚀的分布与地貌、海拔、坡度、坡向等地形因素及与人类的活动密切相关。     

The Influence of Biodiversity Provision on the Cost Structure of Swedish Dairy Farming

Multi‐functionality and the provision of eco‐system services are politically highly prioritised aspects of farming. This study uses a Symmetric Generalised McFadden cost function to analyze the relationship between costs of production and the provision of biodiversity for Swedish milk farms. Biodiversity indicators are based on the number of valuable plant species present at the farm and are modeled as an output in the cost function. The results show that the marginal cost of biodiversity increases with higher provision, and that an increased provision of biodiversity also increases the costs of market commodities such as milk and beef. The upward slope of the marginal cost of biodiversity and its competitive relationship with market goods questions the efficiency of support schemes based on voluntary programmes with a flat‐rate per hectare compensation. Instead, the results support targeted environmental policy schemes with zonings and/or the use of biodiversity indicators.     

Valuing financial,health, and environmental benefits of Bt cotton in Pakistan

Data from a farm survey and choice experiment are used to value the benefits of Bt cotton in Pakistan. Unlike previous research on the economic impacts of Bt, which mostly concentrated on financial benefits in terms of gross margins, we also quantify and monetize health and environmental benefits associated with technology adoption. Due to lower chemical pesticide use on Bt cotton plots, there are significant health advantages in terms of fewer incidents of acute pesticide poisoning, and environmental advantages in terms of higher farmland biodiversity and lower soil and groundwater contamination. Farmers themselves value these positive effects at US$ 79 per acre, of which half is attributable to health and the other half to environmental improvements. Adding average gross margin gains of US$ 204 results in aggregate benefits of US$ 283 per acre, or US$ 1.8 billion for the total Bt cotton area in Pakistan.     

水土保持在城市绿地规划设计中的应用

城市绿地的建设虽然可以在短时间改善城市植被覆盖率,提升人均绿地面积,但是其是否可以起到有效地防治水土流失的作用则是一个关键的问题。通过分析城市绿地可能发生水土流失的原因,探讨了在城市绿地中水土保持措施的布置原则,并且提出了水土保持措施的设计方法,以期为城市绿地规划设计进一步提供科学指导。     

An econometric model for ex ante prediction of wildfire suppression costs

This paper develops an econometric model that can provide predictions of fire suppression costs (per acre and in total) for a given large fire before final fire acreage is known. The model jointly estimates cost per acre and acreage equations via Maximum Likelihood, accounting for sample truncation based on final fire size. Formulas and results are shown for predictions of costs and fire size for wildfires in general, and for large fires in particular. Marginal effects of explanatory variables on cost and acreage are discussed. The distribution of these model predictions illustrates the importance of accounting for sample truncation when generating predicted outcomes based on ex ante information.     

Determination of yield and erosion damage functions using subjectively elicited data: application to smallholder tea in Sri Lanka

Tea has been Sri Lanka's major export earner for several decades. However, soil erosion on tea-producing land has had considerable on-site and off-site effects. This study quantifies soil erosion impacts for smallholder tea farms in Sri Lanka by estimating a yield damage function and an erosion damage function using a subjective elicitation technique. The Mitscherlich-Spillman type of function was found to yield acceptable results. The study indicates that high rates of soil erosion require earlier adoption of soil conservation measures than do low rates of erosion. Sensitivity analysis shows the optimum year to change to a conservation practice is very sensitive to the discount rate but less sensitive to the cost of production and price of tea.     

Quantifying the impact of farmers' social networks on the effectiveness of climate change mitigation policies in agriculture

To reduce agricultural greenhouse gas (GHG) emissions, farmers need to change current farming practices. However, farmers' climate change mitigation behaviour and particularly the role of social and individual characteristics remains poorly understood. Using an agent-based modelling approach, we investigate how knowledge exchange within farmers' social networks affects the adoption of mitigation measures and the effectiveness of a payment per ton of GHG emissions abated. Our simulations are based on census, survey and interview data for 49 Swiss dairy and cattle farms to simulate the effect of social networks on overall GHG reduction and marginal abatement costs. We find that considering social networks increases overall reduction of GHG emissions by 45% at a given payment of 120 Swiss Francs (CHF) per ton of reduced GHG emissions. The per ton payment would have to increase by 380 CHF (i.e., 500 CHF/tCO₂eq) to reach the same overall GHG reduction level without any social network effects. Moreover, marginal abatement costs for emissions are lower when farmers exchange relevant knowledge through social networks. The effectiveness of policy incentives aiming at agricultural climate change mitigation can hence be improved by simultaneously supporting knowledge exchange and opportunities of social learning in farming communities.     

水土流失景观空间自相关与自相似的尺度特征分析——以长汀县根溪河小流域为例

基于遥感、地理信息系统和景观生态学研究方法,对长汀县根溪河小流域水土流失景观格局空间自相关与分形结构及其在不同粒度下的变化特征定量分析表明,水土流失景观中的强度以上流失类型空间自相关最低而自相似性最高;空间自相关性和自相似性依赖于粒度的选择,Moran's I与各种景观类型的FRAC_AM均存在尺度效应;空间自相关随粒度增加呈下降趋势;不同景观类型的自相似性随尺度的变化没有统一规律,但多数第一个较明显的转折点出现在粒度大小为10m处。     

Estimating the economic cost of weeds in Australian annual winter crops

An analysis of the annual costs of weeds in seven winter crops across Australia demonstrated that the most important 15 weed species cause substantial annual costs in both financial and economic terms. Using survey data captured over the 1998–1999 growing season, the financial cost of these weeds in seven crops was estimated to be AU$1,182 million. The main components of this cost were herbicides (AU$571 million), the competitive effects of residual weeds (AU$380 million), and tillage (AU$206 million) while weed contamination of grain was a minor cost (AU$25 million). Across all regions, the most economically important weeds were annual ryegrass, wild oats, and wild radish, although there were regional differences in importance. An economic surplus analysis determined the annual economic cost of weeds in annual winter crops to be AU$1,279 million. This surplus loss represented 17% of the gross value of Australian grain and oilseed production in 1998–1999. Australian grain producers incurred a major loss, with a reduction in producer surplus of AU$1,047 million. Australian grain consumers had a large consumer surplus loss (AU$229 million), while international consumers suffered a small loss and international grain producers gained a small producer surplus from the higher grain prices.