226 POTATOES 



potatoes an annual rotation is possible. As soon as the early crop 

 is harvested a winter cover crop is started. This is turned under 

 as green manure before planting the next crop of potatoes in the 

 spring. For late potatoes, which may occupy the ground until 

 nearly freezing time, a longer rotation is necessary. 



The growth of potatoes without commercial fertilizers is very 

 successfully carried on if an annual crop of green manure is plowed 

 under and barnyard manure is liberally used. When these con- 

 ditions are not secured commercial fertilizer may be profitably 

 used. This is practically true for the growth of early potatoes. 

 For such a crop on a good sandy loam, growers often use as much 

 as 800 to 1200 pounds per acre of the following mixture: Nitrate 

 of soda, 100 pounds; sulfate of ammonia, 100; bone tankage, 100; 

 acid phosphate, 500; and sulfate or muriate of potash, 200. This 

 mixture has a formula of about 4:8:10. If green manure and some 

 barnyard manure are used the chief fertilizer to be purchased 

 would be acid phosphate, or rock phosphate. 



The use of lime on potato soils is not to be recommended. If 

 it be applied the year that the potato crop is grown it is likely to 

 cause a development of the scab disease. 



Preparation of Soil. Potatoes prefer a loose, open soil, and 

 to secure this it is common to plow the field in the spring not 

 long before time for planting. The plowing should be as deep 

 as possible without turning up too much of the poor subsoil. 

 Deep tillage disk plows prepare the soil well by thoroughly mix- 

 ing all parts together. Deep plowing is always better suited to 

 rich soils. If an ordinary turning plow is used the ground should 

 be disked before planting. This treatment is also beneficial when 

 the field has been plowed the preceding fall. After this a smooth- 

 ing harrow may be used. 



Seed Potatoes. Much attention should be given by potato 

 growers to the matter of good tubers for seed. In Chapter 

 III the hill-row method of improving the yield is described. 

 Southern growers often buy seed potatoes from northern states. 

 This is because the southern-grown seed has a tendency to ' 'run 

 out," and the yield is often less than with northern-grown 

 potatoes. Many carloads of seed are shipped to the South from 

 Minnesota, Wisconsin, Michigan, Maine and New York. Another 

 cause for using northern-grown seed is the inability to store seed 

 potatoes from one season until the next. Storage companies take 

 advantage of this and are able to buy southern-grown potatoes, 



