June, 1940] Experiments With Potatoes 5 



"The surface 6 inches is brown or dark brown loam, and the sub- 

 soil to the depth of about 18 or 20 inches is yellowish-brown firm loam to 

 silt loam, and between about 20 and 30 inches the subsoil is friable, yel- 

 low, fine sandy loam. The substratum is compact, platy, fine sandy till. 

 It is hard but breaks readily into firm angular plates about ^4 i"ch thick 

 and 3^ inch across." 



It is this compact substratum that imparts good waterholding capacity 

 to the Paxton loam, but at the same time probably renders it somewhat 

 more susceptible to erosion than if the subsoil were loose and more per- 

 meable to water. 



These two soils are similar with respect to crop producing ability, al- 

 though they are derived from slightly different kinds of rock. Worthing- 

 ton is formed from a fine grained schist with some lime influence ; and 

 Paxton from a mica schist which under the same climatic conditions 

 would probably develop into a more acid soil. 



The Worthington soil of the Jackson farm lies at an elevation of 1700 

 feet and is roughly about 125 miles north of the Lane field which has an 

 elevation of only 650 feet above sea level. Under the climatic conditions 

 that prevail, the Jackson field has been more heavily leached so that the 

 soil, unlimed, has a pH value of about 4.8, whereas the pH of the Lane soil 

 is al)0ut 5.2 unlimed. Lower prevailing soil temperatures on the Jackson 

 field permit the accumulation of more organic matter than on the Lane 

 field. 



Rotations 



The rotations followed in these two tests have been very similar. Both 

 fields were divided into plots, and the plots arranged in blocks so that po- 

 tatoes, oats, and hay could be grown each year in the three-year rotation. 

 All the fertilizer used was applied to the potato crop, the oats and hay be- 

 ing grown on any residual fertilizer left from the potato crop, and on the 

 plant food these crops might extract from the soil itself. 



Lime was applied to certain series on the Jackson field at the rate of 

 two and four tons per acre, not immediately preceding the potatoes, but 

 to the oats at the time the oats and clovers were seeded. Only one appli- 

 cation of lime at this rate was made during the first twelve years, but at 

 the end of the six year period lime was applied to other plots at the rate 

 of 500 and 1000 pounds per acre. Again there was but one application 

 made during the second six-year period. On the Lane field, lime was used 

 at the rate of 500 and 1000 pounds, but only once on the limed plots dur- 

 ing the six-year period studied. 



Timothy was used with the clover seedings on the Jackson farm, while 

 on the Lane field an alsike and red clover mixture was used. 



The rotation on the Jackson field prior to 1928 was typical for the 

 region, and consisted of one or two years in potatoes followed by a hay- 

 seeding in oats, which was then left in hay for seven or eight years. Dur- 

 ing the life of the hay stand, it was customary to top-dress the field with 

 manure every year, or at least every two years. 



The previous rotation on the Lane field was similar to that of the 

 Jackson farm, one year or at the most two years in cultivated crops, then 



