Dec. 1909.] 



POTASH IN CLAY LOAM SOILS. 



51 



Table X. — Comparative Effect of Lime on Feldspar^ Clay, and 

 Feldspar and Clay Mixed in Water. 



Grams Feldspar. 



Orams Clay. 



Grams Lime. 



Soluble Potassium 

 in Grams. 





 

 30 

 30 

 30 

 30 

 30 

 30 



25 



25 



25 



25 



















.0012 

 .0009 

 .0060 

 .0052 

 .0056 

 .0060 

 .0126 

 .0132 



These three series of experiments show and explain a num- 

 ber of interesting soil conditions. When soils ^re limed the 

 potassium does not become soluble and disappear because of the 

 clay, which in turn reduces the solubility. It is because of the 

 action of the clay that lime does not apparently increase 

 the water soluble potassium in the soils. In certain felds- 

 pathic soils with a low percentage of clay there is little doubt 

 but that the effect of lime would be to largely increase the 

 amount of water soluble potassium. As yet we have not ex- 

 perimented with such soils. The presence of the clay unmistak- 

 ably is >the principal factor in conserving the soil fertility. In 

 addition to absorbing the natural potassium it is elsewhere 

 shown that the same influences are exerted on the artificially 

 supplied potassium fertilizers. Further experiments show that 

 the general effect of nitrate of soda and sodium phosphate is to 

 increase the amount of soluble potassium in the feldspars, but 

 this effect is not evident when these are applied to soils. The 

 general effect of clay seems to be a tendency to lower the solu- 

 bility of the soil minerals. This effect is more easily observed 

 when clay is mixed with lime and water. Under such condi- 

 tions the lime in solution may be only about one thirteenth as 

 much as when lime is dissolved in pure water in the absence of 

 clay. 



LIME AFFECTS THE MOVEMENT OF WATER. 



As has been mentioned elsewhere, a continuous movement of 

 soil water is in progress. After rains the excess of water perco- 

 lates downward through the spaces between the soil grains. At 

 other times the movement of the water is upward toward the 



