Date of Graduation


Document Type


Degree Type



Davis College of Agriculture, Natural Resources and Design



Committee Chair

Sven Verlinden.


Season extension methods have been used in many climates and crops for centuries on all scales of vegetable production. Our research compared the effect of six season extension methods on soil and ambient temperatures and yields of warm and cool season vegetables in organic production. The methods under investigation in field plots were row cover, row cover with water tubes, low tunnel, low tunnel with water tubes, and a control for comparison, which were all replicated three times in field plots. The cold frame, and cold frame with water buffer treatments were replicated once in separate structures. Radishes, lettuce, peppers, tomatoes, and arugula were grown in the spring and fall of 2006 and the spring of 2007. Plantings were scheduled according to the level of protection expected for each treatment. Air and soil temperatures were measured throughout the growing seasons. Both early (harvested before the control) and total fruit, root, and leaf yields were recorded. Air and soil temperatures in the experimental treatments were generally higher than the control. Cold frame temperatures were the highest, followed by row covers and low tunnel temperatures, which were sometimes similar to the control. The inclusion of water in plastic tubes showed trends toward increased temperatures, but these trends were rarely significant. The total yields for warm season crops in the field plot treatments were higher than the control. Cool season crops in the field plot treatments did not show differences only trends towards increased yield because of their lower temperature requirements. The total yield in the two cold frame treatments was higher than the field plot treatments in all crops for both years. Early fruit yields were higher for the warm season crops in the field plots and in the cold frames, with much higher early yields observed in the cold frames. The water tubes in the field plots significantly increased yields in pepper crops for both years even though temperature was not always affected. Harvests were extended for up to four weeks in the spring. These results show potential for extended growth and profitability, especially in warm season vegetable crops using season extension methods. Yield increases were most pronounced in the pepper crop. Cold frame treatments showed the highest yield and profitability. Row covers with water tubes would be a lower cost alternative to cold frames if lower initial costs are desired.