Crested wheatgrass arrived in North America at the turn of the twentieth century through the foreign plant exploration missions sponsored by the United States Department of Agriculture. During the first two decades of the new century, scientists tested the grass at agricultural experiment stations. They determined it was useful for grazing and particularly valuable because it could grow in drought conditions with little or no care and would continue to produce high quality feed even after several years of heavy use. Beginning in the 1930s federally sponsored land utilization and agricultural adjustment programs sponsored the use of crested wheatgrass for soil conservation and weed control. The grass protected the soil on the land that had been entered into the acreage reserves and the conservation reserves programs of the federal soil bank. Also in the late 1930s and through the 1960s, rangeland managers used crested wheatgrass to improve forage productivity on public lands that were used for grazing. By the 1970s somewhere between 12 and 20 million acres of crested wheatgrass grew in North America in eleven western states, and in Saskatchewan and Alberta. By 1980 attitudes about agriculture and wilderness had changed in the United States and land management was focused on multiple uses and on protecting ecosystems and native species. Attitudes about grazing and agricultural landscapes had changed and many preferred nonagricultural landscapes and land uses. As a result, crested wheatgrass went from being considered one of the most valuable plants in North America to being considered an invasive weed, in some quarters. Debates in the last 25 years have tried to determine if, where, and how crested wheatgrass belongs in North America. This thesis explains the discourses, or interest groups, that are participating in the current conversation. One impulse is to use empirical evidence to determine whether or not introduced plants like crested wheatgrass belong, but the main contention of this thesis is that empirical studies alone will always be insufficient measures because belonging is also a subjective and experientially or emotionally derived measure.

This study evaluated the potential of using the Surface Energy Balance Algorithm for Land (SEBAL) as a means for estimating evapotranspiration (ET) for local and regional scales in Southern Idaho. The original SEBAL model was refined during this study to provide better estimation of ET in agricultural areas and to make more reliable estimates of ET from other surfaces as well, including mountainous terrain. The modified version of SEBAL used in this study, termed as SEBALID (lD stands for Idaho) includes standardization of the two SEBAL "anchor" pixels, the use of a water balance model to track top soil moisture, adaptation of components of SEBAL for better prediction of the surface energy balance in mountains and sloping terrain, and use of the ratio between actual ET and alfalfa reference evapotranspiration (ETr) as a means for obtaining the temporal integration of instantaneous ET to daily and seasonal values. Validation of the SEBALID model at a local scale was performed by comparing lysimeter ET measurements from the USDA-ARS facility at Kimberly, Idaho, with ET predictions by SEBAL using Landsat 5 TM imagery. Comparison of measured and predicted ET values was challenging due to the resolution of the Landsat thermal band (120m x 120 m) and the relatively small size of the lysimeter fields. In the cases where thermal information was adequate, SEBALID predictions were close to the measured values of ET in the lysimeters. Application of SEBALID at a regional scale was performed using Landsat 7 ETM+ and Landsat 5 TM imagery for the Eastern Snake Plain Aquifer (ESP A) region in Idaho during 2000. The results indicated that SEBALID performed well for predicting daily and seasonal ET for agricultural areas. Some unreasonable results were obtained for desert and basalt areas, due to uncertainties of the prediction of surface parameters. In mountains, even though validation of results was not possible, the values of ET obtained reflected the progress produced by the refinements made to the original SEBAL algorithm.

There are a number of factors that influence crop yield, two of which are soil moisture and fertility.

In the semi-arid west, moisture is often the limiting factor in plant growth. High crop production is dependent upon rainfall and supplemental moisture supplied through irrigation. Plants for these areas, which are most efficient in use of water, other things being equal, would be more desirable.

Wheat is the most important cereal crop in the world. It is the principal staple food in Russia, United States, China, Canada, India and a number of other countries. Covered smut is one of the most serious disease of wheat all over the world. According to Woolman and Humphrey (82) it was known from very early times and is referred to by Theoprastus and other early Greek Roman writers.

Corn occupies from 25 to 30 percent of the crop land harvested in the United States. In recent years the acreage devoted to corn in this country has been decidedly greater than that devoted to any other cultivated crop. In 1944 its dollar value exceeded the combined values of wheat, barley, rye, grain sorghums, and cotton. Although South Dakota lies on the northwestern fringe of the corn belt, the corn crop is one of the most important in that state. Corn production in that area is somewhat unstable because of drought. Corn often fails to reach full maturity before the first frost in the fall. This is particularly true when frost comes unseasonably early. An irrigation project has been proposed for the James River Basin Area of South Dakota. It is a part of the Missouri River Basin Development Project. The introduction of irrigation into this area can somewhat lessen the dangers of drought and early frost. Moisture requirements of the corn crop can be met by proper water applications. In this way the threat of crop failure as a result of drought can be reduced. The corn maturity can be hastened through correct land management and irrigation practices, thus alleviating the danger of early frost. Very little information is available regarding the management of corn grown under irrigation in the Northern Great Plains Region. The problems associated with corn production are peculiar to that area. More complete information is needed concerning the specific needs of the corn crop in the James River Basin. The work reported here shows some of the relationships between the development and growth of corn and soil moisture supply. The objectives of the study were twofold: to determine the periods of corn development in which abundant moisture is most critical, and to determine the effects of a limited moisture supply at various growth stages upon the development and production of hybrid corn. The results of field and greenhouse studies are reported.

The beneficial effects obtained from the application of farmyard manure to the soil have long been known in Utah, but now the point has apparently been reached where it becomes evident that the supply of manure is hardly adequate in some sections where intensive cropping is predicted. The use of commercial fertilizers to increase crop yields is a new practice in Utah agriculture as is shown in Table 1 from an estimate made from data kindly furnished by the Columbia Steel Company, and Porter Walden Company.

Kochia scoparia (L.) Schrad. has had limited use as a forage crop during the past fifteen. years in parts of the western United States, Canada, and Argentina. Erickson and Moxon (1947) reported kochia* to be a good emergency feed for sheep and cattle during dry years in South Dakota. Salguero (1946) said that this species could be utilized in Argentina as silage or pasturage if harvested before flowering. Bell, et al. (1952) in Saskatoon, Canada studied this species in a comparison with other introduced plants and reported that it seemed to have desirable nutrient characteristics for livestock roughage. Plummer (1949) reported beef cattle in Ephraim, Utah had eaten and gained normally on kochia hay.

No other forage crop cultivated in the United States can be used in as many ways as alfalfa. The variety of its uses make it a most useful forage crop. The distribution of alfalfa is world wide and it plays a leading role in the production of livestock and their products. For general feeding of farm animals, alfalfa is unsurpassed. Used for pasture, it has a high capacity, which leads to large gains in grasing animals. If properly rotated and cared for, it adds nitrogen to the soil in a form that is available to plants and thereby increases crop yields. In addition to these assets, alfalfa is a valuable source of essential nutrients and vitamins for livestock.

The gaseous plant hormone ethylene is a small molecule that regulates developmental change. Research was conducted in three areas: sensitivity, synthesis, and alterations to synthesis. Vegetative pea plants were more sensitive than radish plants to atmospheric ethylene. Light intensity did not affect ethylene sensitivity. Ethylene synthesis rates were measured for unstressed cotton, corn, soybean, and tomato plants. The per-plant ethylene synthesis rate ranged from 0.1-80 pmol plant-1 s-1. However, when normalized to net photosynthetic rate, this range was 1-4 µmol of ethylene synthesis per mol of CO2 uptake. Diurnal cycles in ethylene synthesis were present in all crops studied. These cycles were disrupted by drought stress and were attenuated when synthesis rates underwent large changes. Drought stress decreased synthesis in cotton. Flooded corn and soybean had increased synthesis. Blocked perception had no effect on ethylene synthesis or net photosynthetic rate in healthy unstressed plants.