A STUDY OF FACTORS INFLUENCING THE YIELD OF POTATOES 1239 



better depth to plant than 3 inches. Macoun's yields decreased rapidly 

 in the plantings that were deeper than 6 inches. Zavitz (1916), using the 

 clay loam soil at the Ontario station for seven years, planted seed 1, 3, 5, 

 and 7 inches deep, and' practiced level cultivation. He obtained the best, 

 and practically equivalent, yields from planting 3 and 5 inches deep. He 

 noted that when his seed was planted either shallower or deeper than 4 

 inches, the new tubers showed a tendency to develop nearer the 4-inch 

 level than at the depth of planting. 



The evidence presented in the foregoing experiments indicates that, 

 depending to some extent on the soil type and the kind of tillage, the yields 

 are usually better when the seed is planted about 4 inches deep than when 

 it is planted either shallower or deeper. The fact that tubers tend to 

 form near the 4-inch level, irrespective of depth of planting, is in itself an 

 indication that soil moisture and temperature are the most favorable at 

 this depth. While seed planted deeper is normally subjected to tempera- 

 tures too cool for rapid growth, and the resulting crop forms too deep to 

 be dug easily, seed planted less deep is subjected to a greater fluctuation 

 in moisture and temperature, resulting in ill-shaped tubers and very often 

 in a high proportion of sunburned or even blighted tubers. 



In this investigation an attempt was made to determine whether soil 

 type and method of planting have any influence on depth of planting. 

 The average depth of planting in each region, by machine, by hand, and 

 for the region, is shown in table 69: 



TABLE 69. DEPTH OF PLANTING IN THE FOUR REGIONS SURVEYED 



Of the four regions, the deepest planting is found on Long Island and 

 the shallowest in Franklin and Clinton Counties. Inasmuch as the 

 potato soils of these two regions are lighter than those of either Steuben or 

 Monroe County, no influence of soil type on depth of planting is evident 

 in this study. The only significant influence of method of planting on 

 depth is in Franklin and Clinton Counties, where machine-planted potatoes 

 were placed, on the average, 0.7 inch deeper than those planted by hand. 

 Whether or not the average depth of planting shown for each region 



