NITROGENOUS FERTILIZERS FOR GROWING TOBACCO 



By A, B. Beaumont and M. E. Snell^ 



Herein are reported the results of four experiments with tobacco in which 

 the nitrogenous component of the fertilizer used or the method of its applica- 

 tion was the variable factor. Specifically, the elects of the following factors 

 on yield and grading quality were studied: 



1. Quantity of nitrogen applied. 



2. Form of nitrogen applied. 



3. Ratio of organic to inorganic nitrogen. 



4. Method of applying fertilizer. 



The type of tobacco, soil, and general field technic used in these experiments 

 were the same as or closely similar to those used in experiments with cropping 

 systems for tobacco, described in a previous bulletin of this station (4 . Such 

 supplemental details as are necessary for an understanding of the work are 

 presented later in connection with the report on the several experiments. 



Quantity of Nitrogen Applied in Fertilizer^ 



This experiment was started in a preliminary way in 1926. In that year it 

 included a variation in the method of topping tobacco, and therefore the 

 results of 1926 are not included in this report although they were in general 

 alignment with those of the later years, 1927 - 1931. The fertilizer used car- 

 ried 140 pounds of phosphoric acid (P2O5) supplied by precipitated bone; and 

 175 pounds of potash (K2O) of which 26.7 pounds came from cottonseed meal, 

 and the rest was equally divided between sulfate of potash-magnesia and 

 nitrate of potash. The nitrogen in the fertilizer came from the following 

 sources: Iq from cottonseed meal, 1,4 from calurea, about 1'7 from nitrate of 

 potash, and the remainder from nitrate of soda. Nitrogen was applied at the 

 following rates: 61.8, 123.5, 164.7, and 205.9 pounds per acre.' These plots 

 were in quadruplicate and were one fortieth of an acre in size. 



The yield and grade of cured tobacco produced in this experiment for the 

 years 1927-1931 inclusive are presented in Table 1, and shown graphically in 

 Figure 1. The average yields from the different quantities of nitrogen show 

 diminishing returns with increasing amounts, as was to be expected. The 

 yield curve shows the typical sigmoid form for plant growth. Extrapolation 

 of this curve indicates that the maximum yield might be expected with an 

 application of about 250 pounds of nitrogen. 



The curve for the grade index is of the same general type as that for yields, 

 but the maximum was reached with the application of 164.7 pounds. From 

 that point on, the grading quality of the tobacco diminished fairly rapidly. 

 The explanation of this decrease is to be seen in the percentage of the different 

 grades shown in Table 1. The percentage of "lights" (L), "mediums" (M), 

 and "long seconds" (LS), the most influential grades in determining the grade 

 index, taken collectively, increased about 43 percent between the lowest and. 



' Formerly Professor of Agronomy and Technical Assistant, respectively. 



2 This experiment was planned and conducted from 1926 through 1929 by Dr. J. P. Jones. 



' When the experiment was started it was common usage to express the nitrogen content of 

 fertilizers in terms of ammonia (NH3). The amounts of nitrogen used correspond respectively 

 to 75, 150, 200, and 250 pounds of ammonia. 



