12 



The brands of fertilizer showing a low activity of their water insoluble organic 

 nitrogen were just one-half the number noted during the previous season. The 

 manufacturers involved were four, as against seven in 1925. 



Cost of High-Analysis vs. Low-Analysis Fertilizers. 



Although the above figures are presented largel}^ as a means of effecting a com- 

 parison of similar data from year to year, yet they also serve to emphasize the 

 advantage of purchasing the high-analysis mixtures. 



The purchase of mixed fertiUzers should be governed by content and proportion 

 as well as the actual cost of the plant food elements. Low ton cost on low-analysis 

 mixtures may, and usually does, mean excessive cost for actual plant food received. 

 Ton prices are valuable in comparing mixtures of similar grade. Avoid the low- 

 analysis (less than 14 per cent of available plant food) mixtures. 



Explanation of Tables of Analyses. 



The column headed "Grade of Fertilizer" gives the minimum guarantee of 

 ammonia, available phosphoric acid and potash, always stated in this order. To 

 convert ammonia to equivalent nitrogen, multiply by the factor .82. 



In the table headed "Mixtures Showing a Commercial Shortage of SI or More 

 per Ton," under the heading "Approximate Commercial Valuation per Ton," 

 is found the sum of the valuation of each plant food element calculated on the 

 basis of analysis and trade values adopted for 1926, which appear on a preceding 

 page of the bulletin. 



In the same table, under "Approximate Commercial Shortage per Ton," is 

 shown the commercial valuation of the deficiencies or tests found below the guaran- 

 tee, per ton of fertilizer, the value of overruns being used in all cases to offset 

 valuation of shortages. 



Under "Nitrogen" the column headed "Proportion in Water Soluble Form" 

 includes both the mineral and the water soluble part of the organic nitrogen, both 

 of which are readily available. Under " Quality of Insoluble Nitrogen " in all of the 

 tables of mixed fertilizers, passed indicates an activity of 50 or over by the alkaline 

 and 80 or over by the neutral permanganate method ; inferior indicates an activity 

 below 50 and below 80 by the two laboratory methods. All samples are passed 

 which show an activity of the water insoluble nitrogen of 80 per cent or better by 

 the neutral method, even though they maj^ have shown a test below 50 per cent 

 by the alkaline method. All samples are passed which show the sum of the mineral, 

 water soluble organic, and active water insoluble organic nitrogen equivalent to the 

 minimum guarantee. 



Under "Mixtures Showing a Commercial Shortage of $1 or More per Ton," 

 and "Mixtures Seriously Out of Balance but not having Commercial Shortage," 

 deficiencies are emphasized by boldface type. 



In those tables headed "Mixtures Substantially Complying with Guarantee" 

 in the column marked "Form of Potash," the word muriate means that enough 

 chlorine was found present to unite with all of the potash (K2O) found, and it 



