RESPONSE OF POTATOES TO FERTILIZERS 



by Ford S. Prince, Paul T, Blood, and Thomas G. Phillips 



During the past twelve years investigations concerning the response 

 of potatoes to various fertilizer elements have been under way in New 

 Hampshire. The first test of this nature was started in 1928 on the Jack- 

 son farm in East Columbia, near Colebrook, New Hampshire. A second 

 similar experiment was set up on the Lane farm, in Chichester, near Pitts- 

 field, New Hampshire in 1933. 



Both experiments embodied a three-year rotation of potatoes, oats, 

 and hay. In the Jackson farm trial, timothy was included in the hay mix- 

 ture while on the Lane farm clover only was seeded, although both red and 

 alsike clovers were used. The Jackson field has run through four courses 

 of this three-year rotation, while the Lane farm has run through tw^o ; and 

 in both cases, potatoes, oats, and hay have been grown each year. 



Besides fertilizer formulae and rotation problems, inquiries into cer- 

 tain other phases of potato growing have been made. The use of mag- 

 nesium and boron in the fertilizer mixture, the relationship between scab 

 occurrence and soil pH ; and lately, the influence of variety as well as fer- 

 tilizer variations on potato quality have been studied. 



Studies of organic matter have also been made on soil samples taken 

 at the beginning and end of the trials in both cases in order to note the 

 effect of such rotations on the maintenance of organic matter ; and, in addi- 

 tion, to find out what influence the different treatments have had on this 

 important soil component. It is our purpose in this bulletin to discuss 

 these researches, to present data covering any significant facts that have 

 developed, and to draw such conclusions as seem warranted from the work 

 that has been done. 



Description of Soils 



In view of progress made in the soil survey of New Hampshire, we 

 are able to classify and describe the soils of the Jackson and Lane farm 

 fields. In the fortlicoming report of the Coos County soil survey, B. H. 

 Williams. Division of Soil Survey, United States Department of Agricul- 

 ture, describes the ^^VJrthington loam soil found on the Jackson farm thus : 



"Worthington loam. The Worthington loam in cultivated fields has 

 a brown or dark brown surface soil 7 to 8 inches deep (plow depth), which 

 is mellow and inclined to a w^eak crumb structure. This rests upon yel- 

 lowish-brown loam. This, at about 11 to 12 inches depth, passes into 

 olive or greenish-yellow loam of the same structure, which, at 14 or 15 

 inches, passes into greenish-gray, firm, l)ut friable till. The soil through- 

 out is strongly acid. 



"Under forest conditions the Worthington loam has a definite podzol 

 profile development. The gray surface layer beneath the forest litter or 

 (hifif is 1 to 2 inches thick, which changes to a dark brown or cofTee-brown 

 layer about 1 inch thick ; and this, in turn, to a rust-brown layer about 2 

 inches thick, before passing into the yellowish-brown subsoil. Under cul- 

 tivation the gray and brown layers lose their identity through mixing, and 



