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January, 1925
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
93
The Quality of Organic Nitrogen in Fertilizers’ By Firman E. Bear THEOHIOSTATE UNIVERSITY, COLUMBUS, OHIO
HE fertilizer industry desires to be known as a “chemical” rather than as a “scavenger” industry. An examination of the statistics of the sales of fertilizer materials in the United States seems to justify the use of the former term, since a very large percentage of these materials are inorganic compounds, such as calcium phosphate, potassium chloride, and ammonium sulfate. Organic ammoniates, which have long been a “bone of contention” between agronomists and fertilizer salesmen, are not used in such relatively large amounts as was once the case. It has been argued, therefore, that the question of the availability of the nitrogen in the organic ammoniates no longer merits extended consideration. I n a recent article Kadish2 discusses the fertilizer value of the activated sludge which is being produced in Milwaukee and suggests that the quantity of this material that may ultimately be available for fertilizer use may be quite large. (The estimate per capita per annum is placed a t 135 pounds.) Considering also the possibilities in the production of garbage tankage, one wonders whether the fertilizer industry may not be more, rather than less, of a scavenger industry as time goes on. When we remember also that enormous quantities of peat and muck are available for use, it seems doubtful whether we can safely ignore the question of availability of the nitrogen in mixed fertilizers. The present method of testing the quality of organic nitrogen satisfies the requirements in a routine chemical laboratory. By the use of the alkaline and neutral permanganqte tests, organic ammoniates can be classified roughly as to the quality of their nitrogen. At the last meeting of the Association of Official Agricultural Chemists the following statement of interpretation of analyses made by this method was adopted:
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(a) The methods shall be used only on mixed fertilizers containing water-insoluble nitrogen amounting to one-third or more of the total nitrogen found. The nitrogen shall be passed as satisfactory in mixed fertilizers if more than two-thirds of the total nitrogen guaranteed is water-soluble. ( b ) . The water-insoluble nitrogen in mixed fertilizers showing an activity of 50 per cent or more by the alkaline permanganate method, or 75 per cent or more by the neutral permanganate method, shall be classed as “satisfactory.” The nitrogen showing activities below these figures shall be classed as “inferior.”
Subsequently the National Fertilizer Association accepted this interpretation without modification. Unfortunately there is a tendency to confuse the terms “solubility” and “availability.” The foregoing test classifies organic ammoniates on the basis of the solubilities of the nitrogen of their water-insoluble residues in the pcrmanganate solution. The figure thus obtained cannot logically be added to the percentage of water-soluble nitrogen in order to determine the quantity of available nitrogen. Keither solubility in water nor in permanganate solution is a quantitative index of availability. I n addition to the solubility tests there must be some further test which determines the rate a t which the nitrogen becomes usuable to the plant. The only suitable laboratory test so far devised for this purpose is that of nitrate accumulation, and this is not entirely satisfactory. 1 Presented before t h e Division of Fertilizer Chemistry a t t h e 68th Meeting of the American Chemical Society, Ithaca, N. Y.,September 8 t o 13, 1924. 2 A m . Fertilzzer, 60,No. 13,78 (1924).
The following data, secured in a preliminary study of the quality of organic nitrogen in the Soils Laboratory of The Ohio State University, are presented as being of interest in this connection. There is nothing particularly new in the procedures employed, nor do the data permit of drawing any conclusions which have not previously been drawn by other workers. Yet several points are worthy of consideration. For example, 92 per cent of the nitrogen of the cyanamide and 35 per cent of that of the horse manure were soluble in water; yet, by the nitrate accumulation test, the availabilities of the nitrogen in both these substances seemed quite low. The water-soluble nitrogen in the alfalfa was apparently quite easily nitrified. Increasing the amount of water in the soil reduced the nitrate accumulationto verysmall amounts in most cases; yet considerable amounts of the nitrogen of sulfate of ammonia were changed to nitrates a t a water content of 43 per cent. TESTSO F QUALITY O F FERTILIZER NITROGENO Nitrate accumulation as per- Percentage centage of nitrogen added to soils of total with water content varying as nitrogen follows: b soluble in 23% 28% 33% 38% 43% water
Percentage of insoluble nitrogen soluble in permanganate solution
SOURCE OF NITROGEN Ammonium sulfate 112 118 93 27 19 100 Sodiumnitrate 110 115 91 54 49 100 Dried blood 82 81 61 7 4 4 76 Cottonseed meal 69 69 43 5 5 10 67 Activatedsludge 66 66 60 4 4 3 65 Alfalfa hay 60 62 56 6 5 32 28 Muck 39 39 39 5 5 4 41 Garbage tank26 28 20 5 5 15 31 age Cyanamide 7 6 6 5 3 92 .. Horsemanure 4 4 3 4 3 34 30 a Analyses made by Paul H. Mautz. b Twenty milligrams of nitrogen applied in each case. Soil was Wooster silt loam t o which had been added suitable amounts of CaC03 and Caa(PO&. Incubation a t room temperature. Time of accumulation, 3 weeks.
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The writer believes that this problem merits rather extended consideration by agronomists. The researches of Wagner in Germany and of Hartwell and his associates in America, have been of value, but they need to be extended to answer the question as to what one can afford to pay, relatively, for this or that carrier of nitrogen. If, as has been suggested by others, such factors as the crop, the temperature, the texture of the soil, its content of water, its reaction, and perhaps others are involved, we should know more about them. The fertilizer manufacturer is inclined to use from 100 to 200 pounds of organic ammoniates if the analysis permits. Good condition in fertilizers is desirable, but it should be possible to evaluate the nitrogen as such and then to calculate what must be charged against fertilizer condition. The permanganate test is useful, but extended studies of the more important commercial carriers of nitrogen are needed in order to determine the conditions under which they can be used to best advantage. Local Section of American Institute of Chemical Engineers Organized in Chicago-This is the second of such sections to be established, the other one being a t Detroit. The Chicago local section has a membership of about thirty. For the year 1925 the following officers have been chosen: Chairman, F. I ,. Dunlap; Vice Chairman, F. E. Dodge; Secretary-Treasurer, G. B. James.
