24 



N. H. AGR. EXPERIMENT STATION. 



[Bulletin 170 



ing the solubility of potassium when feldspar is stirred with clay 

 and calcium oxide follow: 



Table XVIII 



The data in Table XVH and Table XVIII were obtained by 

 placing the different combinations in a thermostat at room tem- 

 perature and stirring until there was no further action. 



These data show conditions which may be met with in soil 

 studies and why it is difficult to eliminate them when making 

 comparisons. The mineral feldspar has a certain solubility as 

 regards potassium when the solvent is pure water. The addi- 

 tion of calcium oxide, sodium nitrate and other salts increases 

 the solubility very greatly. The presence of clay decreases this 

 effect. All soils, except the pure sands, contain some clay, there- 

 fore the solubility of the minerals in the soil is affected by the 

 clay and is different from what would be expected from the pure 

 mineral. At present, it is not known whether the clay decreases 

 the action of the solvent or whether it removes the potassium 

 from solution as rapidly as it dissolves. The latter seems the 

 more probable. 



In the field a number of plots have been under observation. 

 These plots represent nearly all types of New Hampshire soils 

 and were selected with care, particularly in regard to uniformity 

 of soil and cultural conditions. These plots have been fertilized 

 with nitrate of soda, acid phosphate, and sulphate or mu- 

 riate of potash. Where used, nitrogen has been applied at the 



