A STUDY OF FACTORS INFLUENCING THE YIELD OF POTATOES 1171 



TABLE 14. RELATION OF SOIL TYPE TO YIELD ON 253 MONROE COUNTY FARMS IN 1913 



PLOWING 



The study of plowing aS to its bearing on yield is treated under two head- 

 ings time of plowing and depth of plowing. The average date of plow- 

 ing was obtained by averaging the actual dates of plowing for each region. 

 It is recognized, of course, that this date will vary from year to year, 

 depending on seasonal conditions. The only region in the State in which 

 fall plowing was done to any appreciable extent was Franklin and Clinton 

 Counties. To determine the depth of plowing, the grower was in each 

 case asked to give his estimate of the actual depth, in inches, which he 

 plowed for potatoes. 



Time of plowing 



For many years, such advantages as increased liberation of plant food, 

 elimination of injurious insects, and improved soil texture, have been 

 pointed out in favor of fall plowing. Very little experimental evidence 

 has been presented, however. Dickens (1914) has furnished data covering 

 two years of work at five substations in Kansas, all showing a decided 

 increase in yield on fall-plowed as compared to spring-plowed land for 

 potatoes. A summary of the data on the season at which potato land 

 was plowed in each of the surveyed regions in this study is given in 

 table 15: 



