60 EXPERIMENT STATION. [Jan. 



As compared witli the ]>revioiis year the guarantees have not 

 been as generally maintained. Thirty-six more brands were 

 found deficient in nitrogen and 10 more in available phosphoric 

 acid than for the season of 1910. The brands showing a com- 

 mercial shortage were 17 more than during the previous year; 

 in many cases, however, the commercial deficiency was small, 

 amounting to less than 25 cents j)er ton. 



Table ahowing Commercial Shortages {25 Cents or Over) in Mixed 

 Complete Fertilizers for 1910 and 1911. 



Some brands have suffered serious deficieucies in some ele- 

 ment of plant food without showing any commercial shortage, 

 the deficiency being made up by an overrun of some other cle- 

 ment. This is due, probably, either to carelessness or poor mix- 

 ing rather than a disposition to furnish less plant food value 

 than is called for in the guarantee. It furnishes a condition not 

 to be commended, however, as the fertilizer may be rendered 

 seriously out of balance. 



(h) Quality of Plant Food. 

 (1) Nitrogen. — Sixty or more per cent, of the total nitrogen 

 in the average mixed fertilizer is derived from organic sources, 

 and until recently it has not been possible to tell the consumer 

 much concerning its activity or immediate availability. Hereto- 

 fore there has been published the nitrogen from nitrates and 

 ammoniates as well as the water soluble and water insoluble 

 organic nitrogen. It has seemed evident, however, that some 

 of the brands contained at least a portion of their nitrogen in 

 low-grade forms, but a lack of a suitable method of analysis 

 has rendered it impossible to procure sufficient evidence to defi- 

 nitely substantiate the supposition. In 1910 the chemists in 

 charae of the fertilizer control work in New Eni>'land, New York 



