A STUDY OF FACTORS INFLUENCING THE YIELD OF POTATOES 1243 



a slightly higher marketable yield from deep cultivation and a slightly 

 higher total yield from shallow cultivation. 



Information on depth of cultivation in the four regions surveyed, was 

 obtained in relative terms, denoting general depth rather than actual 

 inches. The variation in depth thruout the growing season was noted also. 

 It has therefore not been possible to make any definite correlation of this 

 factor with yield in these studies, because of the fact that much variation 

 in opinion may have existed among growers as to just what constituted 

 deep, medium, or shallow culture. Furthermore, it is a common practice 

 in all four regions to ridge the rows more or less late in the growing season. 

 This practice really amounts to a deep cultivation at the center of the row 

 while little or none is given close to the plants. Altho considerable varia- 

 tion in the depth of cultivation was found at' different times during the 

 growing season, a plurality of the growers practiced relatively deep early- 

 season cultivation and shallow late-season cultivation. This would seem 

 to be good cultural practice, inasmuch as deep tillage early would enlarge 

 the soil area suited to tuber and root development, while shallower tillage 

 later would avoid undue root pruning and disturbance after tuber forma- 

 tion. 



The practice with respect to this factor, and its apparent influence on 

 yield in each of the regions, is shown in table 74. Of the 1290 growers 



TABLE 74. RELATION OF SEASONAL DEPTH OF CULTIVATION TO YIELD IN THE FOUR REGIONS 



SURVEYED 



