486 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



sandy loam of North Carolina, the Clyde loam and Dunkirk clay of 

 New York, the Dutchess loam of New Jersey, the Frankstown loam 

 of Pennsylvania, the Clarksville stony loam and Greenville loam of 

 Alabama, the Clarksville silt loam of Kentucky, and the Dekalb silt 

 loam of West Virginia, etc. In all these soil types the response to 

 diflferent fertilizers was studied and the fact det(>rmined whether the 

 soil was in need of liming and whether it responded most to a nitrog- 

 enous, a potassic, or a phosphatic fertilizer and what was the best 

 ratio of these constituents. In addition to the lines of work here 

 enumerated, a number of other lines are in ])rogress in the labora- 

 tory and in the field bearing on the influence of fertilizers on soils 

 and other soil ameliorations. 



SOIL- WATER INVESTIGATIONS, 1910-11. 



Field investigations were conducted early in the year, chiefly in 

 Kansas and Colorado, and office researches were continued during 

 subsequent months. The field work brought out more clearly than 

 before the natural development of the soil-forming deposits and 

 the topographic features of the central plains region, together with 

 the relations between the soils and the ground water. Through this 

 region the subsoils and underlying formations are permeated by a 

 body of moisture collected largely in the Rocky Mountains and per- 

 colating slowly (at rates determined by perviousness of the mate- 

 rials) eastward at depths below the surface, varying with the topo- 

 graphic configuration, this subterranean water generally saturating 

 the strata and forming a sort of reservoir supplying artesian and 

 other wells and approaching the surface to within reach of capil- 

 larity, thereby supplementing the local rainfall. Several of the 

 formations permeated by the subterranean waters abound in soluble 

 minerals (salt, gypsum, etc.), which are slowly dissolved and either 

 washed out in the springs, to be carried off through surface streams, or 

 swept seaward at depths beneath the surface. Such solvent action of 

 subterranean waters is well known, but in the central plains region 

 the proportion of soluble matter is so large and so related to other 

 factors that its removal becomes a distinctive geologic agency. As 

 the solution of rock matter proceeds the strata are weakened, and 

 from time to time they slump beneath their own weight and that of 

 the superposed deposits in such manner as to warp the strata, and 

 frequently produce depressions (ranging from steep-sided pits to ill- 

 defined basins) of the surface, when the local run-off following 

 storms accumulates within these depressions and gradually fills them 

 with silt eroded from the rims and neighboring uplands. So char- 

 acteristic is this process, that the general surface over thousands of 

 square miles (excepting the immediate valleys of the few rivers, like 

 the Arkansas, fed chiefly from the mountains) is of a distinctive 

 topographic type — coalescing basins and low divides forming an 

 irregular surface without continuous seaward slopes. The condi- 

 tions by which this topography was produced have existed for ages — 

 indeed, throughout the greater part of the vast interval since the 

 Cretaceous — and during these ages the progressive slumping in the 

 deep-lying strata, with the subsequent warping of the surface and 

 shifting of local areas of erosion and deposition, have resulted in an 



