Virginia is a net deficit state in corn and soybeans. The purpose of this study is to determine when during the crop year this deficit occurs, the relationship among production, consumption, and storage to determine if storage is a limiting factor, and why Virginia does not increase its production of these grains to meet the needs of its livestock poultry industries. Three sectors are considered in the study. These are the livestock and poultry industries which are the consumers of corn and soybeans, the corn and soybean production sector, and the storage sector. Trends in livestock and poultry show that from the 1965-1969 period to the 1975-1979 period there have been increases in the number of animals consuming feed and, in most cases, decreases in per head consumption of feed. Changes in production show increases in both acreage harvested as well as yields per acre over the same period. The result of these changes is a decrease in the corn deficit and relatively little change in the soybean deficit. Storage capacity has also been increased. On a state-wide basis, storage is adequate to meet the needs of the producers; whereas, in some regions it proves restrictive. A study of the movement of corn and soybeans indicates the costs of shipping these grains within the state are, for the most part, more expensive than importing the needed quantities from the Mid-West. / Master of Science

A model to predict the daily green leaf area index (GLAI) for corn has been developed for Indiana conditions. Using daily maximum and minimum temperatures the GLAI was predicted for the vegetative stage, reproductive and grain filling stage, and the leaf senescing stage of corn. Predictions of GLAI for corn can be made on a daily basis from the day corn is planted until it is harvested for grain. The GLAI model was tested under Virginia conditions using green leaf area measurements collected from corn plants grown on Davidson silty clay loam, Davidson silty clay, and Mayodan sandy loam soils in the Piedmont region of the State. Maximum and minimum temperature data were also collected at the three sites. Measurements were made for two growing seasons using corn hybrid Pioneer 3369A, three plant population densities and two irrigation schedules. Short duration temperature data were also collected to compare with the daily maximum and minimum temperature data for the Mayodan site. Also a combination of soil temperature at 10 cm depth and air temperatures were used for the temperature functions accumulated from date of planting at the Mayodan site. Results of this study show that the predicted and measured GLAI values compare favorably under irrigated conditions on the Davidson soil. The results were not as favorable on the irrigated corn on the Mayodan soil. When the corn is subjected to severe moisture stress on either soil, GLAI cannot be predicted with this model. Short duration temperature data resulted in a better prediction of GLAI on the Mayodan soil. When applying nitrogen fertilizer to the corn through the irrigation system through the grain filling stage, the measured GLAI values compared favorably with the predicted GLAI values. However, the application of nitrogen and sulfur fertilizer together resulted in GLAI being maintained above that predicted for a longer period of time during the grain filling stage before its decline. / Ph. D.