Linear economic models were utilized to predict effects of various environmental control policies on individual firms. Four different linear models were specified and in some instances relatively minor changes in specification were made which resulted in additional sub-models. Models varied as to numbers and types of fixed factors, variable cost relationships, market products, and fixed factor requirements. Once each model or sub-model was described five or six policies were theoretically applied to that model. Policies used were: taxing market products, taxing variable factors, taxing a non-market externality (external diseconomy), a standard on the quality of the externality, subsidizing variable factors and subsidizing fixed factors. It was assumed that the non-market externality would be produced in a fixed ratio with market products. Furthermore, the assumption was made that alternative production techniques were available to the firm. The important aspect of the various techniques was that the proportion of the externality generated by a market product varied by production method. Consequently, strong emphasis in the analysis was placed on determining whether or not a given policy could induce the firm to switch to a lower externality generating production method. In addition to the strictly theoretical analysis a linear irrigated farm model was described. The farm model produced irrigation return flows which were considered to be creating stream pollution. From the theoretical analysis likely policies for controlling return flows were ascertained. Some of these policies were then applied to the farm model. Specifically, a water tax (variable factor tax) and a constraint on delivered water were administered to the farm model. Based on the theoretical analysis taxing market products did not appear to be a particularly desirable policy. For some models, the market product tax actually increased externality production. A tax on externality production (effluent tax) seemed to give the most consistent effects of all policies across all models. The externality tax either reduced or had no effect on externality production. The biggest shortcoming of the externality tax appeared to be administrative. Before the tax can be used the externality must be identifiable as to source. Consequently, a search was made for policies which generated results similar to the externality tax yet were not subject to the same administrative problem. It appeared that under specific conditions a variable factor tax, a tax on specialized fixed factors or a combination of a tax-subsidy scheme could be effective alternative policies. However, these latter policies, if improperly applied could result in increased externality production. Taxes as high as 65 cents per acre inch of water were applied to the farm model. Depending on assumed conditions the water tax resulted in reduced irrigation return flows. When labor was constrained tax levels needed to be higher to reduce return flows compared to the case where labor was not constrained. Placing a restraint on delivered water also reduced return flows. Again, when labor was constrained this policy was not as effective as when labor was unconstrained. The water tax policy reduced net returns to the farm model considerably more than the constraint on delivered water. The main difference in net revenues was attributable to the total water tax bill rather than reductions from other added costs and/or enterprise changes. / Graduation date: 1972

Thesis (Ph. D. (Plant Production))--University of Pretoria, 2001. / Adobe Acrobat Reader needed to open files.

Nitrogen (N) cycling involves the gains, losses, and transformations of N from sources such as soil organic matter, crop residues, and fertilizers. These sources are the primary N supplies potentially available to non-leguminous crops. Through the use of a stable N isotope tracer (¹⁵N), transformations among various soil N pools can be studied. We conducted three separate studies using ¹⁵N. Two studies dealt with methodologies of ¹⁵N use and analysis, while the third study investigated mineralization of ¹⁵N labeled crop residues under field conditions. The first study evaluated a new apparatus for applying ¹⁵N by fertigation to subplots under buried drip irrigation. We determined that this method was an effective means of uniformly applying tracers using buried drip irrigation. The second study evaluated a new method for fine-grinding soils based on particle size distribution and variability of organic N and ¹⁵N analyses. Soils of varying texture were rapidly ground to achieve acceptable analytical precision for N and ¹⁵N analysis. The objectives of the third experiment were to: (i) evaluate mineralization of inorganic N from ¹⁵N -labeled crop residues with different C/N ratios and at different loading rates and (ii) evaluate the influence of residue loading rate and type on the percent net mineralization from ¹⁵N-labeled crop residues in a basin irrigated wheat cropping system in Southern Arizona. Mineralization of crop residues in this hyperthermic soil was rapid and was often followed by periods of re-immobilization. Net end-of-season mineralization of residue N was 30-50% for lettuce, and 30-40% for wheat.

Project Completion Report, OWRT Project No. A-050-ARIZ. / Agreement No. 14-31-0001-5003 / Project Dates: July 1974 - June 1976. / The work upon which this publication was based was supported in part by funds provided by the Office of Water Research and Technology (A-050-ARIZ), U.S. Department of the Interior, Washington, D.C., as authorized by the Water Research and Development Act of 1978. / INTRODUCTION: The use of treated sewage effluent by the Buckeye Irrigation Company began with 800 acre -feet in 1962 and had increased to 40,000 a.f. by 1968. The effluent was diverted by the Buckeye Irrigation Company from the Gila River approximately seven miles below the City of Phoenix 91st Avenue treatment plant, as it became available at their diversion point. Natural streamflow, used in earlier years, had virtually stopped due to upstream development except in heavy runoff years such as 1941. The ground water in the district of the Buckeye Irrigation Company is relatively high in dissolved solids. The quality of the treated effluent is better. In 1971 the company signed a 40 -year contract with Phoenix to assure its use of 30,000 a.f. of effluent per year. The effluent is mixed with native ground water to bring the total water applied on the 18,000-acre district up to approximately 90,000 a.f. (Halpenny, 1973). The treated effluent use by the Buckeye Irrigation Company is the largest in the State of Arizona and one of the largest land applications of treated effluent in the United States. It is unique in that it is being utilized by an irrigation district. Most other uses have been by city operated farms or private farms under a single ownership. In spite of its uniqueness the effects of effluent use by the Buckeye Irrigation District had not, prior to this research, been well documented. This documentation was made in order to improve the general knowledge needed to extend this type of use to other areas in the state and nation. "Widespread consideration and utilization of land application cannot be made until such time as adequate information concerning the technique involved is made available. The experience gained by those who have successfully utilized this wastewater management should be used... specific evaluation of established systems in the various climatic zones would appear to be more fruitful than new research installations for determining long term effects on soils, vegetation, ground water and the indigenous ecology..." (Sullivan, et al., 1973). During the two year research period most of the initial objectives were achieved. The original specific objectives were: 1. To identify changes during an extended period of application of treated wastewater to irrigated fields in: a. irrigation practices b. cropping patterns c. fertilization practices d. crop yield response and quality e. quality of irrigation water, and f. soil properties. 2. To make a preliminary evaluation of the effects of the use of effluent on ground-water conditions. 3. To make a preliminary evaluation of changes in water costs and farm profits.

No description available.

Thesis (M.S. - Agricultural Economics)--University of Arizona, 1985. / Includes bibliographical references (leaves 114-115).

Thesis (M.Ag.Sc.)--University of Adelaide, Dept. of Agricultural Business, 1997. / Bibliography: leaves 146-153.

Thesis (P.h. D.)--University of Colorado, 1982. / Includes bibliographical references (leaves [231]-240).

Thesis (M. Dev. Studies (Development Studies))--University of the Free State, 2002. / Word processed copy. Includes bibliographical references (leaves 73-78).

Thesis (M.Inst.Agrar.)(Agricultural Economics)--University of Pretoria, 2005. / Includes summary. Title from opening screen (viewed March 20, 2006). Includes bibliographical references (leaf 61).