NITROGENOUS FERTILIZERS FOR TOBACCO 13 



The conditions and practices of tobacco culture most comparable with 

 those of the present experiment are to be found at the Tobacco Experiment 

 Station of Connecticut. This station has reported (2) the results of the first 

 three years of an experiment with different quantities of fertilizer nitrogen. 

 Nitrogen was applied at the rates of 100, 150, 200, 250, and 300 pounds per 

 acre. The results were generally similar to those reported in this bulletin. 

 The highest yield was obtained from the largest quantity of nitrogen, but the 

 highest grade index was obtained from an intermediate quantity, namely 200 

 pounds. 



The experiment with the different forms of nitrogen supplying one half the 

 nitrogen while the other half was supplied by cottonseed meal shows that, 

 with the possible exception of ammonium sulfate, any one of the carriers used 

 in the experiment may safely be used to supply at least one half the nitrogen 

 of tobacco fertilizer for a limited period. This statement assumes soil and 

 other conditions closely similar to those under which the experiment was 

 conducted. The excellence of nitrate of soda was shown, which was reflected 

 mainly in the grade index. This evidence should tend to dispel the prejudice 

 against this form of nitrogen which is held in some quarters of the Connecticut 

 Valley. 



The results of the experiment with different ratios of organic and inorganic 

 sources of nitrogen are very interesting as showing to what extent the propor- 

 tion of organic nitrogen may be reduced without reducing the yield and grading 

 quality of the crop. On the basis of only four years' data we are not convinced 

 that it would be sound practice to reduce the percentage of organic nitrogen 

 to the low point (12.5) indicated. However, from this and other experiments 

 conducted at this station, it appears entirely safe to reduce the proportion of 

 organic nitrogen to one half. Very likely, on soils of medium and heavier 

 texture, and when cover crops are grown to supply organic matter, the content 

 of organic matter in the fertilizer may well be reduced to one fourth. 



Inorganic nitrogen and that in the synthetic organic forms such as calcium 

 cyanamid and urea are generally much cheaper, pound for pound, than that 

 in the natural organic forms such as cottonseed meal. Obviously, it is to the 

 advantage of the grower to substitute the cheaper forms of nitrogen in his 

 fertilizer when it can be done without materially reducing the value of the 

 crop. From 1926 to 1936 the average percentage of water-insoluble organic 

 nitrogen in mixed tobacco fertilizers sold in Massachusetts decreased from 

 56.6 percent to 50.4 percent, this decrease being due primarily to the substi- 

 tution of the water-soluble organic forms. In view of the results from the 

 present experiments, this trend in the source of nitrogen in tobacco fertilizer 

 appears to be in the right direction. 



The response to row application of fertilizer was less marked than was 

 expected in view of results from an earlier and similar experiment with corn 

 (7). In the latter experiment, however, fertilizer was used at a much lower 

 rate than with tobacco, and this probably accounts for the difference in the 

 results. Special attention is directed to the attachments devised for row 

 placement of fertilizer in this experiment. By means of these it was possible 

 to place the fertilizer accurately and easily in the desired position. The ma- 

 chine has possibilities for use with other plants than tobacco. 



