NITROGENOUS FERTILIZERS FOR TOBACCO 3 



second highest quantity of nitrogen, and then decreased about 5.4 percent 

 between this point and the maximum quantity of nitrogen. The percentage of 

 "darks," taken collectively, steadily but slowly increased between the lowest 

 and highest quantities of nitrogen, although the percentage of "long darks" 

 reached a maximum with 164.7 pounds. Collectively, the percentage of 

 "seconds" did not vary a great deal from one treatment to another, although 

 there was a steady and marked increase in the percentage of "long seconds" 

 from the lowest to the highest amount of nitrogen. The percentage of 

 "fillers" and "brokes" decreased from the lowest to the highest quantity of 

 nitrogen, but there was little decline in the percentage of these grades be- 

 tween the next highest and highest quantities. 



Tleld Grade Crop 

 Index Index 



17E0 .400 600 



1500 .350 600 



1250 .300 400 



Pounds of Nitrogen 



Figure 1. 



Variations in Yield, Grade Index, and Crop Index of Tobacco with 

 Increasing Quantities of Nitrogen. 



Since the market value of a cigar-wrapper type of tobacco such as was 

 grown in this experiment is determined not only by the grade index but also 

 by the size of the crop, the crop index, which is the product of yield in pounds 

 per acre and the grade index, must be taken as the final criterion in adjudging 

 the economic value of a given factor of production. It may be seen from the 

 table and graph that the maximum crop index was reached with the second 

 highest quantity of nitrogen, 164.7 pounds. The first increment of nitrogen 

 raised the crop index 23.9 percent, and the second increased it 18.9 percent. 

 However, the nitrogen increments were not equal, and, as the graph shows, 

 the rate of increase was slightly greater with the second than with the first 

 increment. 



