Models simulating crop growth offer an opportunity to fill important data gaps from experimental plots. Examples include incorporation of many weather conditions as well as alternative management strategies. The simulated data must be reliable, however. This study examined the application of the EPIC growth model to simulate corn (Zea mays L.) yield on the Southern High Plains when water stress was imposed on various dates in the growing season. The EPIC model produced simulated yield distributions with means not significantly (P = 0.05) different from those of the actual data in 2 of the 3 yr considered, and standard deviations of simulated yields similar to those of the actual yields for all 3 yr. Linear regressions of simulated yields on actual yields resulted in slope coefficients not significantly (P = 0.05) different from 1.0 for 2 of the 3 yr. Simulated yields explained 83, 86, and 72% of the variance in actual yields for the 3 yr of measured data. The EPIC model appears useful for further studies of irrigation scheduling for corn.
Traditional methods used to estimate fishing effort that maximizes rent to an open access resource have almost universally assumed all costs are directly proportional to effort. When crews receive a fixed share of gross returns, labor costs are proportional to catch; hence, rent accrues to crews as well as vessel owners under limited entry. A model that allowed costs to be proportional to effort and catch was applied to the Gulf of Mexico shrimp fishery. This study indicates that traditional analysis would result in management schemes that overtax vessels and ignore rent accruing to crews.
The Rio Grande has headwaters in Colorado, flows through New Mexico, and serves as the United States-Mexico border in Texas, emptying into the Gulf of Mexico. Snow melt in Colorado and northern New Mexico constitutes the water river supply for New Mexico and the El Paso region, whereas summer monsoonal flow from the Rio Conchos in Mexico and tributaries, including the Pecos River, provides the Rio Grande flow for southern Texas. The region is mostly semiarid with frequent long-term drought periods but is also characterized by a substantial irrigated agriculture sector and a rapidly growing population. International treaties and interstate compacts provide the rules for allocation of Rio Grande waters between the United States and Mexico and among Colorado, New Mexico, and Texas. Water rights in Texas have been adjudicated, but the adjudication process was based on a wet period; hence, contemporary Rio Grande water rights are overallocated. Issues related to the waters of the Rio Grande include frequent drought, increased municipal demand caused by a rapidly increasing population, supply variability, underdeliveries from Mexico, increasing salinity, inefficient delivery systems, health issues of the population, no economic/financial incentives for farmers to conserve, and water is not typically priced for efficiency. Stakeholders are interested in identifying solutions to limited water supplies while there is increasing demand. There are several activities in place addressing Rio Grande-related water needs, including enhancing delivery distribution efficiency of raw water, conversion of rights from agriculture to urban, improving both agricultural irrigation field distribution and urban use efficiency, developments in desalination, and litigation. None of the solutions are easy or inexpensive, but there are encouraging cooperative attitudes between stakeholders.
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