THE AVAILABILITY OF THE SOIL POTASH IN 

 CLAY AND CLAY LOAM SOILS. 



BY FRED W. MORSE and B. E. CURRY. 



The kinds of soil on which the experiments reported in this 

 bulletin were made are believed to represent the heavy clay or 

 clay loam soil in different parts of the state. They are known to 

 form a large portion of the farms in the vicinity of the experi- 

 ment station, and are recognized by practical men as excellent 

 soils for grass. They were formed from granitic rocks by the 

 grinding action of the glaciers and by weathering, and usually 

 lie upon a foundation of ledge on the uplands and a bed of 

 boulder-clay in the lowlands. In some of the lowland fields 

 the boulder-clay comes so near the surface as to form the subsoil. 



Although these clay loams form a large proportion of the 

 farming land in this vicinity, they are by no means continuous 

 in extent, but are broken by ledge outcrops and knolls or ridges 

 of sandy soil. 



Clay soils formed from granite rocks are naturally rich in 

 compounds of potash because they are principally made by the 

 pulverizing and weathering of the mineral known as feldspar, 

 which is one of the constituents of granite and richest in potash 

 of any of the common minerals. On the other hand, sandy soils 

 are largely formed from quartz, another mineral in the granite, 

 which is harder than the feldspar, does not pulverize as easily 

 and contains no potash. Therefore sandy soils differ widely in 

 chemical composition from clay soils, and the results of these 

 studies on heavy clay loams cannot be applied to light sandy 

 loams. 



A chemical analysis of a soil is of little use, when studied by 

 itself, for showing the needs or capacity of that soil; but it is 

 valuable when taken in connection with field experiments and 

 analyses of crops. Early in the history of the experiment sta- 

 tion several analyses were made of the heavy clay soil of the 

 farm, which showed one per cent, of potash soluble in strong 

 acid. This percentage would be equivalent to twenty tons of 

 potash in the upper foot of an acre of land. This enormous 



