Agro-Climatological Investigations— Bensin 203 



50°F. (io°C.) which is the minimum temperature for growing 

 warm-season crops, like tomatoes, beans, etc. 



The small number of thermal units in this subarctic region 

 indicate thermal deficiency, as this is the most important en- 

 vironmental factor limiting the kind and varieties of crop plants 

 adapted for growing here. Only a limited number of crops 

 and varieties could be grown in this region, selected and ad- 

 justed to this environment by careful acclimatization work. 



According to the German plant physiologist Hildebrandt, the 

 amount of thermal units needed for growing grain crops in the 



Table 3.— Number of thermal units— degree days— in degrees of Fahrenheit 



ABC 

 Base Base Base 



32°F. (o°C.) 4i°F. (5°C.) 50°F. (io°C.) Geographical 



June, July, location of 



Station May to September August the station 



University Exp. Station.. 3145 1763 700 64°5i'N.lat. 



i47°52' W. long. 

 Nenana 3177 1778 736 64°33'2N. lat. 



i49°o6' W. long. 

 Fairbanks 3145 1808 726 64°5o' N. lat. 



1 47°43' W. long. 

 Manley Hot Springs 3040 1640 662 65°oo'N. lat. 



i50°oo' W. long. 

 Tanana 2984 1626 644 65 10' N. lat. 



i52°o6' W. long. 

 Mean 3098 1723 693 



temperate zone of Germany could be designated as 28oo°F. 

 (i6oo°C.) for barley and 3828^. (ig6o°C.) for oats. Accord- 

 ing to G. T. Selianinoff, in European Russia the requirements 

 for barley are 3o6o°F. to 450o°F. (i7oo°C. to 25oo°C.), for 

 wheat 3204°F. to 4o86°F. (i78o°C. to 227o°C.) and oats 

 3492 °F. to 45oo°F. (i94o°C. to 23oo°C.). These European 

 standards of thermal units for grains are very near to those of 

 the American temperate zone. In the Wisconsin Agricultural 

 Experiment Station, for example, average used thermal units 

 base 32 °F. for the grains grown in 1944-1948 were as follows: 

 for barley 2929^. 95 days, for wheat 3373°F. 103 days and oats 

 2823°F. 87 days from planting to maturity. 



