High grade sulpliate of potash . , 



Carbonate of potash 



Muriate of potash 



Sulphate of potash-magnesia* . , 



Kainit 



Silicate of potash 



Carnalite 



.Vote. Taken from 1906 .\nnaal Report of Massachusetts Experiment Station. 



The low grade potash fertilizers, kainit, sylvanite, carnalite, and 

 silicate of potash, contain a large bulk of material of little or no 

 value in connection with their relatively small percentage of potash. 

 They naturally furnish a favorite source of potash for low grade 



fertilizers. 



This element, like potassium, is never found in the 

 Phosphorus, free state in nature but is associated with other ele- 

 ments, largely lime, iron and alumina, and usually 

 in a more or less unavailable form. There is little danger of this 

 element being lost by leaching. 



Phosphoric acid is a term applied to a compound of phosphorous 

 and oxygen, expressed chemically as anhydrous (water free) phos- 

 phoric acid (P.jO-). Phosphoric acid is found in larger quantities 

 in grain and seeds than in the leaves and stems of plants. The soil 

 is therefore exhausted of this element most rapidly by a continued 

 system of grain cropping, especially if the grain is sold from 

 the farm. 



The common sources of phosphoric acid, from a commercial stand- 

 point, are phosphate rock, bones, basic slag and guano. Phosphoric 

 acid may be combined with lime in three different forms: (i) as 

 tri-calcic phosphate, commercially known as in,soluble phosphoric 

 acid or bone phosphate of lime, (2) di-calcic phosphate or reverted 

 phosphoric acid and (3) mono-calcic phosphate or soluble phos- 

 phoric acid. 



Insoluble phosphoric acid. This term is applied to a compound 

 consisting of three parts of lime to one part of phosphoric acid ; in 

 this form it is not readily available to plants. South Carolina, 



* Known frequently as low-grade sulphate of potash. 



