A STUDY OF FACTORS INFLUENCING THE YIELD OF POTATOES 1247 



Stone (1905), in a carefully controlled experiment covering six years 

 at the Cornell station, compared the yields of potatoes from cultivating 

 three, four, five, six, seven, eight, nine, eleven, and thirteen times during 

 the season. During these years he obtained average yields favoring 

 seven, eight, and nine cultivations, by from 8 to 100 bushels per acre. 

 The plots were replicated from two to four times. Stone's tests showed 

 clearly that under the conditions of his experiment it was possible to culti- 

 vate beyond the limit of maximum production. Emerson (1907) compared 

 yields from what he called poor, medium, and thoro cultivation. Under 

 poor tillage, the land was harrowed three times and cultivated twice, the 

 land not being kept free from weeds even early in the season. Under 

 medium tillage, the land was harrowed three times and cultivated four 

 times, the weeds growing only in the rows after the crop was nearly ripe. 

 Under thoro tillage, four harro wings and six cultivations were given, no 

 weeds being allowed to grow. The yield of the medium-cultivated crop 

 exceeded that from poor tillage by 60 per cent and that from thoro tillage 

 by about 9 per cent. Emerson concluded (1) that tillage can be overdone, 

 (2) that cultivation to control weeds only is sufficient, and (3) that, in 

 eastern Nebraska, two or three harrowings and five or six cultivations are 

 sufficient for potatoes. 



The high frequency of cultivation recorded for some of the regions 

 included in this study must not be construed to mean that this frequency 

 applies only to operations with a cultivator. As already explained, all 

 operations which stir the soil and control weeds after planting are included. 

 Inasmuch as the rate of planting and the value of manure and fertilizer 

 have already been shown to be very influential on yield, frequency of 

 cultivation is here studied for each region in connection with these factors. 



Frequency of cultivation on Long Island 



Long Island is the only region, of the four surveyed, in which the Hal- 

 lock weeder is used extensively. This implement is used principally just 

 before or just after the crop comes up. Having a broad sweep, it removes 

 very efficiently those small weed seedlings which develop between planting 

 time and the time at which the plants come up. Since the entire crop in 

 this region is planted in drills, cross cultivation is impossible and much 

 hand hoeing is therefore done to remove the weeds that develop during 

 the growing season. Many growers reported also hand pulling of weeds. 

 These operations, in addition to the usual cultivations between the rows, 

 resulted in the highest frequency of cultivation in this region, the average 

 in 1912 being 10.9 times. 



The relation of this factor to yield, under constant rates of planting, 

 is shown in table 75. The averages for the 329 farms listed in this table 

 indicate that in 1912 it did not pay to cultivate more than ten times. 

 In fact, these averages seem to indicate that frequency of cultivation above 



