Food for essential constituents, but, unfortunately for the farmer, 

 plants they do not require any disclosure whatever as to the 

 232 availability of the most valuable content, viz., Nitrogen; 

 hence, the attempt to state a formula on the bags, or on 

 the tags attached to the latter, is a wholly incomplete 

 affair. As an example, we may take a fertilizer whose 

 formula is 4-8-10, that is, one containing 4 per cent, of 

 Nitrogen, 8 per cent, of phosphoric acid and 10 per cent, 

 of potash. 



Materials of various qualities and grades are em- 

 ployed for the preparation of so-called complete fer- 

 tilizers, as may be seen from the following list: 



Aside from these materials, there are others that are 

 occasionally employed by mixers to furnish filler. 



Availability in Fertilizers. 



In the making of complete goods from the various 

 straight fertilizers the mixer is largely guided by the 

 cost, as well as the quality of the latter. The question 

 of quality is particularly important, since no^ high grade 

 fertilizer can be made from inferior ingredients. The 

 conception of quality has been gradually developed by 

 investigators and farmers and the term Availability is 

 commonly employed when the value of straight or mixed 

 fertilizers is considered. We call a fertilizer Available 

 when the Nitrogen, phosphoric acid or potash contained 



