June, 1940] Experiments With Potatoes 13 



appears to be at the critical point in this respect, the use of lime is to be 

 recommended in quantities small enough so that they will not encourage 

 potato scab, but in sufficient quantity to give assurance that the soil will 

 not become any more acid than it is at present, and especially so that good 

 hay crops will be produced. 



The limed plots on the Lane Farm, like those of Jackson, show no 

 stimulation on the potato crop. 



In a test on the Ireland farm, Greenland, New Hampshire, on land 

 limed at different rates and on which soybeans had been grown the previous 

 year and plowed under, potato yields were increased, apparently because 

 of the increased growth of the soybeans due to liming and the subsequent 

 decay of this crop in the soil. 



*Uniform fertilization except fur previous lime applications. 



Although the \ields were not large, they nevertheless indicate distinct 

 stimulation to the potato crop from the effect of lime on previous soybean 

 growth. Yields of the soybean crop grown in 1933 on this land had been 

 secured by taking square yard samples from each plot in quadruplicate and 

 reducing them to an air dry condition. Because of the interest in this 

 phase the yields of the 1933 soybean crop are given. 



TABLE X. Effect of lime on yields of soybeans, Ireland farm, 1933. 



Treatment Yield, Air Dry Wt. per Acre 



No Lime 966 lbs. 



1 T. Calcium Lime 1661 lbs. 



2 T. Calcium Lime 1863 lbs. 

 2 T. Magnesium Lime 2108 lbs. 



Varying Amounts of Fertilizer 



During the first two rotations on the Jackson farm, different amounts 

 of fertilizer were applied at rates of one-half ton, one ton, and one and 

 one-half tons of 4-8-7 per acre. Yields are reported in Table XI for these 

 varying amounts of fertilizer. 



TABLE XL Four-year average yields of Jackson farm potatoes 

 with varying amounts of fertilizer, 1933-38. 



These data indicate that response is secured for more than one ton 

 of a 4-8-7 fertilizer under the conditions of this test, but show, of course, 

 that additional amounts of fertilizer bring diminishing returns. Both dif- 

 ferences are highly significant. 



