Hay is one of Virginia's important agricultural crops. It ranks third in dollar value, being exceeded in value only by corn and tobacco. The 1948 hay crop was valued at $46,486,000 according to the Virginia Crop Reporting Service (16), and 1,414,000 acres of land were used to produce approximately 1,823,000 tons of hay. As shown by this report, more acres of Virginia's crop land were used to produce hay in 1948 than any other single crop. By using better agronomic practices the hay yield per acre of land used to produce hay has been gradually increased. The climatic conditions found in the southeastern states are among the nation's most favorable for the production of hay, but these same conditions make it almost impossible to cure high quality hay in the field. The average total rainfall for any one month during the hay curing season is not excessive, but the numerous light showers at short intervals make the field curing of hay very difficult. In many instances, hay crops are almost sufficiently field dried for safe storage in the barn when a light shower falls and causes additional hay losses to occur. In 1942 a survey (1) of hay losses was made on 215 farms in nine Southwest Virginia Counties, with the farmers reporting 25% of their crops lost or damaged because of unfavorable weather. In 1948 a survey was made of the hay losses due to weather hazards in all counties of Virginia. The county agents estimated that 31.6% of Virginia's total hay crop was damaged 25%, 15% was damaged 50%, and 4% was a total loss. This report shows that 50.6% of all hay produced in Virginia was damaged 25% or more. Reports from Virginia hay inspectors indicated that only a very small amount of the field cured hay met the requirements for U.S. No. 1 hay. This means that the annual hay losses in Virginia due to weather hazards have been tremendous when it was cured in the field. Agricultural Engineers in cooperation with many organizations have developed barn hay driers as a means of reducing these hay losses. Farmers have been furnished detailed plans and specifications for installing and operating these driers. At the close of the 1948 hay drying season, there were 487 hay driers in operation on Virginia farms. Eighty-three of these systems were installed in 1948. The same survey shows that 456 units were used to dry long hay, 22 baled hay, and 19 chopped hay. Available data (1) shows that barn dried hay will grade from one to two grades better than field dried hay which is harvested from the same field, the only difference being in the method used in curing. The barn dried hay shows a decided advantage over field dried hay when considering the amount of leaves, green color, carotene and protein content retained. The success farmers have obtained by using the forced ventilation method of curing hay has made hay driers very popular. Hay dryers can 7 be used advantageously on many farms that produce hay. This is particularly true when the hay is stored in mows where electric service is available to operate motors. With this system, each mow is considered separately and the air distribution system must be “tailor-made“ to fit the mow. On some farms, the relative location of buildings and fields, availability of electric service, or methods of storing and feeding hay, are such that the typical barn hay dryer is not adaptable. / Master of Science