214 Alaskan Science Conference 



were quite encouraging. The crop of pickling cucumbers 

 planted in the tubs was good. In 1949 galvanized iron reflectors 

 painted with aluminum paint were used successfully in the 

 garden for growing beans. In 1950 several types of solar radi- 

 ators and reflectors were successfully tested with various warm- 

 season vegetable crops. Tomatoes, squashes, pumpkins and 

 cucumbers were grown in the tubs and on the ground with 

 radiators and reflectors, and over 100 pounds of tomatoes were 

 harvested. By means of these reflectors and radiators tempera- 

 ture of the soil was increased 15 above the maximum tempera- 

 ture of air near the surface. 



The real aim of the solar radiators and reflectors is to obtain 

 the additional amount of light and heat needed for growing 

 warm-season vegetables in this region and in other parts of 

 Alaska. All these vegetable crops require mean temperatures 

 above 50°F. (io°C), and more intensive light than the normal 

 of subarctic latitudes since they are of subtropical origin. 

 Assuming that the mean temperature for growing tomatoes is 

 6o°F. we need during the months of June, July and August 

 920 degree days (base 5o°F.), while we have only about 700 

 (see Table 3). Therefore it is necessary to increase the tem- 

 perature of air and soil at least 20%. This can be achieved by 

 means of solar radiators and reflectors. Reflectors and radiators 

 and coal dust scattered on the soil surface actually create a 

 convection current surrounding the growing parts of the plant 

 while the heated soil surface stimulates the growth of the root 

 system. Additional light intensity obtained by reflection stimu- 

 lates the photosynthetic activity of the plant and assists in the 

 accumulation of carbohydrates in the plant as manifested by the 

 remarkable increase in leaf area. Aluminum foil could be used 

 to advantage for construction of hot beds, cold frames and 

 green houses in Alaska with solar reflectors. 



Climate and Crops 



In agronomic work with field crops in Alaska environmental 

 climatic factors are of primary importance. Most of this work 

 is inevitably devoted to the acclimatization of the introduced 



