276 ILLINOIS STATE DAIRYMEN'S ASSOCIATION 



Phosphoric acid is found in different forms in the commei- 

 cial fertilizers offered for sale in the state, viz, in combinations 

 with calcium, magnesium, iron, or aluminum; some of these 

 compounds are soluble and others insoluble. Vv^e distinguish 

 in fertilizer analyses between soluble, reverted, and total phos- 

 phoric acid. Mono-calcium phosphate (containing soluble phos- 

 phoric acid) is soluble in water; di-calcium phosphate (coniani- 

 ing reverted phosphoric acid) is insoluble in water, but soluble 

 in a strong warm solution of ammonium citrate, while the tri- 

 calcium phosphate (containing insoluble phosphoric acid) is 

 not appreciably soluble in either of these liquids. The phosphoric 

 acid contained in raw bone, bone meal, or rock phosphate is in 

 the form of tri-calcium phosphate. When applied to the soil 

 in a fine-ground condition, it is gradually dissolved by the soil 

 moisture and the juices of the plant roots and thus rendered 

 available to plants. Coarse-ground bone, on the other hand, 

 is but slowly decomposed in the soil and therefore of but little 

 value for crop production the first season. Super-phosphates con- 

 tain both water-soluble and citrate-soluble phosphoric acid. 

 Broadly speaking, both of these kinds of phosphoric acid are of 

 about equal value to plants. The phosphoric acid in basic slag 

 (odorless phosphate) is largely soluble in ammonium-citrate so- 

 lution. Available phosphoric acid means the sum of water- 

 soluble and reverted phosphoric acid, and represents the phos- 

 phoric acid of immediate value to plants. The results of the 

 analyses are calculated on a basis of the content of phosphoric 

 anhydrid (P205). 



Potash is readily soluble in water in the compounds usea as 

 potassic fertilizers in our state. Potash is obtained in wood 

 ashes, largely in the form of carbonate, or in various imported 

 potash salts, like crude kainit (containing 12-13 per cent pot- 

 ash), potassium muriate, sulfate, silicate, etc. Since muriates 

 (chlorids) have an injurious effect on the quality of certain 

 crops, notpbly tobacco and potatoes, the use of potash salts free 

 from muriate is in some cases desirable or even essential. The 

 results of the analyses are figured on a basis of the content of 

 potassium oxid (K20). 



