1220 EARLE V. HARDENBURG 



a more comprehensive nature have indicated that equivalent amounts of 

 smaller seed pieces, down to a minimum weight of one ounce, planted 

 closer, may give even more efficient results. With an expensive and 

 limited seed supply, the latter type of seed and system of planting would 

 seem advisable. 



Number of eyes 



Many of the older potato growers attach considerable importance to 

 the number of eyes to be left, in cutting seed potatoes. While a few 

 growers cut single-eye pieces, the majority prefer pieces containing two eyes. 

 Whether or not there is any significance in the relation of this factor to 

 yield or to quality of the crop, it is automatically controlled, in practice, 

 by the size of the seed piece, the importance of which has already been 

 discussed. Arthur (1892) showed, in very definite terms, that the yield of 

 large tubers decreases with the use of seed tubers weighing more than 

 four and one-half ounces. His results are in accord with those of many 

 other experiments which show that increasing the number of eyes on the 

 seed piece tends to reduce the average size of the resulting tubers. 



Whipple (1915) studied the influence of thinning to one stalk per hill, 

 in a two-years test of nine varieties planted from two-ounce pieces irre- 

 spective of the number of eyes. Thinning to one sprout improved the 

 market shape and the uniformity of the crop, but Whipple's results do 

 not justify any conclusion that either total or marketable yield was 

 increased by thinning. The cost of thinning was therefore not warranted. 



Ballou (1910) has shown that varieties differ in the number of stalks per 

 hill which will develop from a given size of seed piece. Bovee, having 

 frequent eyes, developed more stalks per hill per unit of seed piece than 

 did Carman No. 3, a variety of few eyes. Ballou obtained an increase 

 in the unmarketable yield from every increase in size of seed piece or 

 number of eyes in both varieties. The most profitable net yield in the 

 Bovee was obtained from two-eye pieces planted at the rate of 15 bushels 

 per acre, and in the Carman No. 3 from half-tuber pieces planted at the 

 rate of 25 bushels per acre. 



Again it remained for Zavitz (1916) to contribute the real test of the 

 influence of eye frequency on yield, by eliminating the factor of size of 

 seed piece. Using one-ounce seed pieces thruout a five-years test, he 

 compared the results from seed pieces containing one, two, three, four, 

 and five eyes, respectively, and found that as the number of eyes increased, 

 the average total yield increased and the percentage of marketable yield 

 decreased. The difference in marketable yield, however, was in no case 

 more than 5 per cent. It is therefore evident from Zavitz 's work that 

 the yield is proportional to the number of stalks per hill, as well as to the 

 size of the seed piece, and that nothing is to be gained by cutting to a 

 certain minimum number in preparing seed for planting. 



