11 



Inferior Forms of Organic Nitrogen. 



For the past eighteen years or more the quality of the organic nitrogen in mixed 

 fertilizers has been studied by the agricultural chemist. For the past thirteen years 

 this Station has, in the tabulation of the analytical data on fertilizer inspection, indi- 

 cated the quality of the water insoluble organic nitrogen on all brands analyzed. 

 That this _has_ been at least partly responsible for the improvement in the quality of 

 the organic nitrogen which the fertilizers have contained there can be no question. 

 The two laboratory methods commonly used in studying the activity of the water 

 insoluble nitrogen in fertilizers are known as the "Jones Alkaline Permanganate 

 Method" and the "Street's Neutral Permanganate Method." No one having a cor- 

 rect understanding of the matter disputes the chemist's ability by means of these 

 methods to pick out those brands which contain the more inferior forms of water 

 insoluble organic nitrogen. There does exist, however, considerable difference of opinion 

 as to what the results show and how they shall be interpreted. Nitrogen activity by 

 the laboratory methods does not mean the same thing as nitrogen availability by vege- 

 tation tests. In fact, comparisons made on many samples both at the Rhode Island 

 Agricultural Experiment Station and the Massachusetts Station show that the neutral 

 permanganate method gives much higher figures in activity than does the vegetation 

 test in availability. On the other hand, the alkaline permanganate method not infre- 

 quently, particularly in case of mix-tures containing organic vegetable ammoniates, 

 gives considerably lower figures in activity than does the vegetation test in avail- 

 ability. It is generally understood by the trade and by the control chemist that any 

 fertilizer containing its water insoluble nitrogen in forms to give an activity of less 

 than 80 by the neutral and less than 50 by the alkaline permanganate method shall 

 be considered as containing organic nitrogen of an inferior form. Some chemists who 

 are qualified to speak with authority believe that the passing mark in case of the alka- 

 line method should be raised by five points, making it 55 instead of 50. It is not un- 

 common for two chemists in studying the organic nitrogen activity on the same sample 

 of fertilizer to obtain results which vary from one to three points, and in some cases 

 even more; particularly is this apt to be the case if the type of apparatus used in the 

 two laboratories is different. It might also be said that in this as in almost all opera- 

 tions, experience is an important factor. 



In the 1922 fertilizer inspection in this State two brands of fertilizer representing 

 grades 2-8-2 and 2-8-3 were found by the laboratory methods to contain organic 

 nitrogen of an inferior quality. At the request of the manufacturer the sealed dupli- 

 cate samples, as provided by the law, were forwarded to their chemist for checking 

 purposes, who reported back a test of over 50 activity on one of the brands; the check 

 results were, however, under 55 activity in all cases. A study by us of the results of 

 analysis of grades 2-8-2 and 2-8-3 put out by the manufacturer showed that 14 

 brands and 48 samples of the 2-8-2 grade, and 16 brands and 48 samples of the 2-8-3 

 grade had given activities of water insoluble organic nitrogen between 46 and 54 by 

 the alkaline permanganate method. It seemed worth while, therefore, to study the 

 actual crop producing power of the water insoluble nitrogen in these two tj^pes of fer- 

 tilizer, by the use of vegetation tests, in order to confirm the reliability of the labora- 

 tory methods used in detecting the presence of low-grade organic ammoniates. Plans 

 therefore were made to conduct such tests not only with the two brands in question, 

 but also with the various brands belonging to the same two grades that were put out 

 by this company. 



Vegation Test for Nitrogen Activity. 



The soil used for the experiment was taken from one of the Experiment Station 

 fields. No nitrogen fertilizer or animal manure has been applied to this soil since 

 1890. It has received annually durmg this period, 320 pounds of dissolved boneblack 

 (acidulated phosphate) and 160 pounds of muriate of potash per acre. The only 

 nitrogen which the soil has received for nearly a third of a century has resulted from 

 crop residues or natural sources common to fields under usual farm management. 



One part by weight of this soil was mixed with two parts of sifted sand, and forty- 

 three pounds of this mixture was weighed into each pot. 



