The performance of solid-fuel heaters (4-lb petroleum coke bricks) was unsatisfactory only after a long rainy spell just prior to burning, and then because of difficulties at starting time. However, the quality of the material had not suffered from exposure to prolonged hot, cold, or rainy weather. Although 10 bricks give the same heat output as one oil heater, only 150 bricks per acre were needed for a temperature rise normally produced by 25 oil heaters. In calm conditions a need for extra heaters at all borders became evident. However, a reduction in number of bricks toward the center of the plot appears possible since the temperature increased constantly toward the middle of the heated area in these tests.

This study was conducted under project 400 U. The petroleum coke bricks, manufactured under the label “Tree-Heet” were supplied by the Mobil Oil Corporation.

Richard B. Tyree, Norman Ferrari, Russell H. Pleasants of the Department of Viticulture and Enology, and Fred Lory and Donald Huovinen of the Department of Agricultural Engineering assisted in the field work.