Barn and Field Experiments in 1917. 35 



THE POTATO CROP IN ITS RELATION TO SOIL AND 



FERTILIZER. 



If one could only know the exact amount of plant food 

 that a given crop could avail itself of in a given soil the question 

 of application of plant food in the form of a fertilizer would 

 be much simplified. Caribou loam is the potato soil of Aroos- 

 took County. Interspersed with it are patches of greater or 

 less extent of the much less desirable Washburn loam. It is 

 perfectly easy to select typical Caribou loam soils. Will the 

 same fertilizer give the same results — other conditions being as 

 equal as may be — on different fields with this type of soil? 



This Station has made a series of studies upon the need of 

 potash to grow potatoes upon Caribou loam. In 191 7 the divi- 

 sion of Soil Fertility Investigation and the division of Cotton, 

 Truck and Forage Crop Disease Investigations of the Bureau 

 of Plant Industry of the U. S. Department of Agriculture in 

 searching for the probable cause of the "new disease" of pota- 

 toes noticed in 1916 made a series of trials with fertilizers using 

 the triangle scheme that this Station has adopted from them and 

 which is discussed on pages 23 to 26 of this Bulletin. They were 

 interested in comparing results obtained on Caribou loam with 

 those obtained on Washburn. It is interesting to compare the 

 results they obtained on Caribou loam with those obtained by 

 this Station on Aroostook Farm Caribou loam. All of the ex- 

 periments were near Aroostook Farm and had the same weather 

 conditions. The results from Aroostook Farm are given in the 

 column headed A. The other letters refer to the tests made by 

 the Department of Agriculture but the letters used are merely 

 distinguishing but not identifying. They are grouped according 

 to the triangle diagram. (See page 21). 



Hundred weight per acre of potatoes 



Fertilizer treatment 



Three ammonia plots 



157 



95 



93 



39 



Three phosphoric acid plots 



103 



109 



85 



100 



Three potash plots 



115 



123 



116 



79 



Seven check plots 



109 



87 



94 



53 



Six center (Complete) plots 



154 



125 



159 



120 



