Three essays addressing production economics and irrigation: Managing for drought and pests transported in irrigation water.

摘要

his dissertation consists of three essays addressing irrigation issues for two areas of Colorado where irrigated agriculture is predominant. The essays integrate interdisciplinary requirements from agricultural engineering, agronomy and economics.;The first essay uses a FORTRAN alfalfa growth simulation model with alfalfa stem nematode (Ditylenchus dipsaci) (ASN) growth and damage functions incorporated to analyze alfalfa (Medicago sativa L.) production with ASN infestation. The results indicate that growing ASN resistant alfalfa varieties provides higher returns than ASN susceptible alfalfa varieties, although ASN infestation reduces net returns. ASN control activities implemented at the proper time can extend the economic life of an alfalfa stand.;The second essay incorporates the daily biomass from the FORTRAN alfalfa growth simulation model into a spreadsheet for expanded analyses. Independent infected and non-infected alfalfa plant populations were simulated and ASN growth and damage functions were developed. Results show that including a non-host crop in the rotation and planting ASN resistant alfalfa varieties increase returns and provide some control of, but do not eliminate, the ASN. An ASN control activity in the second year of production and multiple ASN control activities increase net returns.;The third essay addresses how agricultural production changes in response to reduced water supplies in the Closed Basin portion of the San Luis Valley of Colorado. A two stage model is developed using the General Algebraic Modeling System (GAMS). The first stage simulates the Doctrine of Prior Appropriation, river flows, net of Rio Grande Compact requirements, and diversions to irrigation ditches to determine the quantity of surface water available for agricultural production. The second stage of the model maximizes net returns to the study area by simulating the cropping patterns on representative agricultural areas.;A 50% reduction in surface water with a full aquifer causes a decline in the value of crop production of