14 MASS. EXPERIMENT STATION BULLETIN 346 



Summary and Conclusions 



Four experiments were conducted in the use of nitrogenous fertilizers in 

 growing Havana Seed tobacco, a cigar-wrapper type. The effects of the fol- 

 lowing factors on yield and grading quality were studied: 1. Quantity of 

 nitrogen applied. 2. Form of nitrogen applied. 3. Ratio of organic to in- 

 organic nitrogen. 4. Method of applying fertilizer. The results of the ex- 

 periments are summarized as follows: 



1. Nitrogen was applied at the rate of 61.8, 123.5, 164.7, and 205.9 pounds 

 per acre. The highest average yield of tobacco was obtained from the largest 

 quantity of nitrogen, but the highest grade index resulted from the use of 

 164.7 pounds. The crop index, the product of yield times grade index, by 

 means of which the crops were evaluated, was highest for this rate (164.7) also. 



2. Four forms of nitrogen, as found in nitrate of soda, sulfate of ammonia, 

 calcium cyanamid, and urea, were compared with each other and with that 

 in a standard mixture. Only one half the nitrogen in the fertilizer was supplied 

 by these carriers, the remainder coming from cottonseed meal. Nitrate of 

 soda gave the best results as measured by the crop index. All carriers pro- 

 duced high yields. The grade index of tobacco grown with sulfate of ammonia 

 was lowest. 



3. An experiment was conducted in which the ratio of organic nitrogen, 

 supplied by cottonseed meal, to inorganic nitrogen, consisting of equal parts 

 from nitrate of soda and ammonium sulfate, varied from 1:7 to 1:1. Good 

 yields and good quality of tobacco were obtained from all treatments, with 

 only insignificant differences in results. A cover crop of oats sown each year 

 may have been an important contributing factor in this experiment. 



4. In comparison with the usual method of broadcast application, fertilizer 

 was placed in bands near the plants at the time of setting, by means of special 

 attachments built onto the transplanter. During the first two years of the 

 experiment the results favored row application; but considering the experi- 

 ment as a whole, broadcast application gave best results. However, the 

 experiment showed that small amounts of fertilizer applied near the plants 

 were proportionately more effective than large amounts broadcast. 



From these experiments it was learned in addition: that the amount and 

 distribution of rainfall during the growing season of tobacco are important 

 factors influencing both yield and grade of tobacco; that for best results a 

 comparatively high level of nitrates must be maintained in the soil during the 

 period of most rapid vegetative growth; and that the form of fertilizer nitro- 

 gen used bears little or no relation to brown root-rot of tobacco. 



The results of these experiments appear to warrant the conclusion that a 

 comparatively high rate of application of fertilizer nitrogen is necessary for 

 growing Havana Seed tobacco of high yield and quality, and that no more 

 than one half and probably as little as one fourth of the nitrogen need come 

 from organic carriers such as cottonseed meal. This recommendation assumes 

 soil and other conditions closely similar to those of these experiments. 



