62 PLANT SUCCESSION AND CROP PRODUCTION 



farms in the northwestern section are on former prairies now 

 drained, seem more suitable for clover production. In southeastern 

 Ohio the soils are porous enough for the growth of the nodule form- 

 ing bacteria and clover could be doubtless grown with the liberal 

 use of lime and a crop occasionally plowed under for green manure. 



(e) Potatoes 



Potato production in Ohio also centers in the northeastern 

 part. In the United States the potato crop seems to follow popu- 

 lation more than any special climatic or soil factor. We find a small 

 center of potato production near each of the thirty largest cities of 

 the United States. The east coast of Maine, however, is a famous 

 potato center. This points to a northeastern center for potato 

 production. In Ohio the total production of potatoes in 1915 was 

 7,757,169 bushels. The sectional production can be seen from the 

 following : 



Northeastern section 4,039,487 bushels 



Northwestern " 1,499,446 bushels 



Southwestern " 1,351,122 bushels 



Southeastern " 867,114 bushels 



(f) Tobacco 



Tobacco is in many ways one of our most interesting crops. It is 

 extremely susceptible to the environment and assumes many varia- 

 tions in growth form according to the treatment it has received dur- 

 ing cultivation. In the United States, it centers in Kentucky, Vir- 

 ginia, and North Carolina between the corn and cotton belts. Ohio, 

 Pennsylvania, Wisconsin, and Connecticut also engage in tobacco 

 production. In Kentucky while given more attention in cultivation 

 than corn receives, it is grown nevertheless on an extensive system 

 of farming. Farther north it receives a good deal more care, as 

 much often, as vegetables grown on an intensive system would get. 

 In some places in Connecticut it is grown under cloth shelters. 

 These shelters lower the transpiration rate in the daytime. They 

 also decrease the radiation of heat at night, thus maintaining more 

 equable climatic conditions. The shading increases the size and de- 

 creases the thickness of the leaf thus making a product more suit- 

 able for cigar wrappers. 



The Ohio tobacco center is in the southwestern part of the 

 state — a continuation, as has been pointed out, of the Lexington 



