June, 1940] Experiments With Potatoes 11 



TABLE VI. Effects of lime on 3-year average yields of 

 Jackson farm potatoes, 1930-193- 



It will be noted here that a decrease in yield was shown with the two 

 tons of lime appHcation, and an increase with four tons, although neither 

 difference is significant. In the treatment in which two tons of lime were 

 applied with the fertilizer carrying no potash, the difference of -193 bushels 

 is highly significant. In comparing the yields in this series with the 4-8-0 

 treatment, Table I, it is apparent that the yield of potatoes in limed plots 

 was depressed more than on the series with no lime, the actual yield for 

 the 4-8-0 series during the three years covered by Table VI being 223 

 bushels per acre, or an increase on the plots which had no lime over those 

 which received lime of 30 bushels per acre. This difference was consistent 

 through the years, the unlimed plots always outyielding the limed ones. 



It would appear from these facts that lime serves to depress potash 

 availability, and since potash was omitted from the fertilizer altogether, 

 this depression was serious enough to cause rather large yield differences. 



A great deal of potato scab developed on these plots limed at the two 

 and four ton rates. 



Upon revamping the Jackson farm experiment in 1934, plots were in- 

 cluded which received 500 and 1000 pounds of ground limestone per acre, 

 while all the plots which had previously received two and four tons of 

 limestone were continued during the next six-year period. On the four 

 ton plots, however, aluminum sulphate and sulphur were used on the halves 

 of each plot as acidulating substances to counteract the effects of lime in 

 promoting scab. Yield records are given in Table VII on all these limed 

 series. 



TABLE VII. Effects of lime and fertilizer on 6-year average yields 

 of Jackson farm potatoes, 1934-1939. 



Treatment Yield per acre P. E. Difif. from check P. E. 



The chief interest, perhaps, in using lime in a potato rotation is to 



encourage better hay growth and to produce more crop residues or green 



manures to plow under. While a great deal more clover was produced 



on all the limed plots and increases in hay yields were rather large, it does 



not appear that the lime benefited the potato crop either directly or in- 



I directly through increasing crop residues. Perhaps it should again be noted 



I that in both these tests the first hay crop was cut and removed, but the 



I second crop was plowed under. In both these tests the 500 and 1000 pound 



