36 PRINCIPLES OF FARM PRACTICE 



Besides, in order to hasten matters acid phosphate may be 

 applied as a phosphate fertilizer for the use of the first season's 

 crop. 



It has recently been suggested that the phosphoric acid of 

 phosphate rock may be made available for plant use by 

 mixing it with calcium sulfate, or land plaster. This claim 

 seems to be supported by some experiments made by the 

 Oregon State Agricultural Experiment Station. If this 

 method should be proved successful by experiments in differ- 

 ent parts of the country under a variety of soil and climatic 

 conditions, it might become worth while in general farm 

 practice. To be of practical value, however, the combined 

 cost of the calcium sulfate and phosphate rock should be 

 less than the cost of acid phosphate enough to yield an equiva- 

 lent amount of phosphoric acid. 



POTASSIUM 



The supply of potassium. Potassium occurs in soils 

 usually in considerable abundance, except in very sandy and 

 muck soils. Not much of it is available because it is in- 

 soluble. It seems to be demonstrated by recent experiments 

 that insoluble potassium may be made available through a 

 liberal supply of organic matter. It is a question whether 

 this method -of supplying potassium may be wholly relied 

 upon to furnish all that is needed by crops. It may be worth 

 trying however, for even if it should fail to render much 

 potassium available, it will leave the soil improved because 

 of the addition of organic matter. 



Potassium occurs in large deposits in a few places in the 

 world, the most extensive being found in Germany and in 

 Alsace, France. Until recently most of our potash fertilizers 



