162 STORRS AGRICULTURAL EXPERIMENT STATION. 
The total weight of nitrogen is calculated from the weight 
of crop and the percentage of total nitrogen determined. A 
comparison of the amounts of total nitrogen in the same crop 
from different pots with varying amounts of fertilizer nitrogen 
gives an indication of how much the nitrogen in the crop in- 
creased as the nitrogen in the fertilizer was increased. It will 
be observed that as the moisture content of the sample at the 
time of analysis was not determined the comparison must be 
made between the amounts of nitrogen determined in air-dried 
fodders, that is, in the condition in which they are ordinarily 
used. Past experience has shown, however, that different 
samples of the same fodder when thoroughly air-dried under 
similar conditions differ but slightly in moisture content, the 
differences being hardly sufficient to affect materially the de- 
termination of the proportions of protein. For practical pur- 
poses, therefore, the comparison of the proportions of nitrogen 
as determined in the air-dried samples is sufficiently accurate. 
To compare the effects of the different amounts of fertilizer 
nitrogen upon the feeding value of the crops, the percentage of 
protein in the crops from the different pots was estimated by 
the usual method, by multiplying the percentage of nitrogen 
by the factor 6.25, on the assumption that protein contains 16 
per cent. nitrogen. This method of course is not absolutely 
correct, as pointed out on a preceding page (p. 39). For in- 
stance, not all forms of protein contain 16 per cent. nitrogen. 
On the other hand, a portion of the total nitrogen of some 
crops may frequently be in the form of nitrates, because when 
readily available nitrates are abundant in the soil they may be 
taken up by plants more rapidly than they can be built up 
into plant tissue, and may thus be present unchanged in con- 
siderable amounts,* especially if the plant is harvested in pre- 
mature stages of growth. These nitrates are of no value as 
food for animals. As shown in Table 19 on page 84, some 
of the crops in these pot experiments contained appreciable 
amounts of nitrates, which would affect to some extent. the 
proportions of actual protein present as determined by the 
usual method. However, the method used for estimating 
protein is perhaps sufficiently accurate for practical purposes; 
and since it has been and is still commonly used, it has also 
been followed in this case. 
* See Connecticut Sta. Rept. 1895, p. 108. 
