June, 1940] Experiments With Potatoes 33 



New Hampshire, potatoes planted on different dates were later tested for 

 quality. The variety used in this test was Green Mountain, planted on 



TABLE XXXIV. Quality tests of potatoes planted at different dates, 



1939, Greenland, N. H. 



Date of planting Date of harvest No. tubers tested Quality rating 



Alav 12 October 15 200 82.2 



June 5 October 15 350 89.0 



lulv 1 October 15 270 92.1 



July 1 September 15 10 81.5 



similar land and fertilized in exactly the same way. The season was very 

 dry and potatoes planted May 12 suffered materially from drouth, yield- 

 ing only about one-third as much as those which were planted June 5. 

 while those which were planted June 5 outyielded those planted July 1. 

 Potatoes from May 12 planting showed much "second growth"; those 

 planted June 5 exhibited some second growth, but the July 1 planting was 

 free from this condition. 



Quality ratings of potatoes from the various plantings dug October 15 

 show a higher figure for the July 1 planting, which was the planting that 

 suffered least from adverse weather conditions, while those planted May 12 

 have the lowest rating. A few potatoes dug September 15 from the lot 

 planted July 1 exhibit a quality rating about ten ]~»oints lower than those 

 which were left in the ground and allowed to approach maturity undis- 

 turbed. These data seem to show that any factor which may delay growth 

 in midseason may influence starch formation to such an extent that later 

 amendments cannot be made, and that maturity is doubtless a factor of 

 some importance in determining equality ratings or starch formation. 



With respect to second growth, some "dumb-bell" shape tubers were 

 divided at the line of constriction and subjected to these tests. The seed 

 end of such potatoes proved to have a much higher specific gravity than 

 the stem end. Of samples tested this difference amounted to about 30 

 points in the quality rating, or about 85 for the seed end, 55 for the 

 stem end, and 70 for the potato as a whole. 



The evidence is fairly convincing that there are inherent differences in 

 quality ratings among varieties, as well as variations due to climatic fac- 

 tors, date of planting, and maturity ; and while there is some ground for 

 the belief that certain fertilizers may contribute to variations in potato 

 quality, the fundamental causes underlying the wide variations that have 

 been encountered within a variety still await adec|uate explanation. From 

 reference to Tables XXVI H and XXIX for example, which give the dis- 

 tribution of the potatoes of the samples tested under the various specific 

 gravities, wide variation within each samples is apparent. Tests of pota- 

 toes from the same hill indicate that these variations are to be found there 

 as well and while a given hill or sample ma}' have a high average quality 

 rating, individual tubers within the group may have a relatively low rating. 

 Whether this is due to a difference in time of setting of the tubers, the 

 ability of one potato in the hill to secure a more adequate food supply 

 than another, or whether the position of the potato in the soil with regard 

 to depth that might influence the temperature and the proper assimilation 

 of food materials, has not yet been determined. 



