158 PRINCIPLES OF FARM PRACTICE 



It should result in the development of seed capable of pro- 

 ducing a much higher average yield than that obtained by 

 the usual methods of corn selection. An increase of at least 

 ten bushels per acre is not too much to expect. There is 

 probably no other means of increasing production with as 

 little additional labor and expense as this. 



Four-hill-unit method of improving potatoes by selec- 

 tion. The same principles of selection are used in the 

 tuber-unit method of improving potatoes. The essential 

 features are as follows : 



The initial selection is made in the field of good tubers 

 from high-yielding hills. The tubers selected should each 

 weigh about five ounces, should be entirely free from evi- 

 dences of disease, and should conform to type. 



Each tuber is cut into quarters and planted in four hills, 

 the four hills forming one unit. Other units are planted in 

 the same way, but, to avoid confusion, a greater space is 

 left between units than between the hills of a single unit. 

 For the test plot of the first season at least one hundred 

 units should be started. A system of numbering should be 

 followed in order that an accurate record of each unit may 

 be kept. A careful observation of the plants should be made 

 from time to time, and a record kept of such qualities as 

 vigor, growth, freedom from disease, and of other points 

 that may be of value in determining the best plants. All 

 weak and undesirable units should be eliminated entirely as 

 soon as discovered. This may be done either by checking 

 off their records and paying no more attention to them or by 

 removing the plants entirely. 



Finally, the tubers of each unit are harvested separately 

 and put into a separate bag. Only those tubers of the highest 

 yielding units should be preserved. These should be further 



