406 POPULAR SCIENCE MONTHLY 



Second Year. Grain Crop — Oats. On the Cornell University Farm yields of 

 50 bushels per acre are often secured. 



manner. Such methods are permissible only in a thinly populated 

 country. Some time previous to this some men had noted that in 

 nature the crops grown on a piece of land during a term of years 

 varied, and it is common observation to-day that in the north, hard- 

 wood trees, as oaks, will come in where pines have been cut off. Hem- 

 locks do not succeed hemlocks. And even in grass land marked changes 

 occur in the composition of the herbage. During a period of wet years 

 Eedtop (Agrostis vulgaris) may assume the ascendancy on a piece of 

 land, and lose it just as quickly when an era of dry years occurs. To 

 secure a rotation of crops, it is essential that crops capable of being 

 grown in a district be known and that there be a market for them. 

 Wheat has been and is the pioneer crop of the northwestern parts of 

 this continent. Climatic conditions are important factors in deter- 

 mining the rotation. In Canada, oats, mangels, clover and timothy 

 may be good crops to include, but they would be of little value for the 

 southern states. Cotton, cowpeas and crab grass would be more likely 

 to grow. It was largely lack of knowledge about crops that prevented 

 progress. Clover and turnips were not grown as field crops in Eng- 

 land until about 170 years ago, and even about a hundred years ago, 

 Arthur Young said that probably not more than half the farmers and 

 certainly not over two thirds grew clover, although both turnips and 

 clover were recognized as of value in the sixteenth century, and turnips 

 were used as an article of diet at least as early as 1390. About 1730 

 Lord Townsend introduced on to his barren estate in Norfolk what has 



