FIELD EXPERIMENTS WITH FERTILIZERS. pete ts. 
of dry matter, and the amounts of protein per acre are calcu- 
lated by multiplying the estimated weight of dry matter in the 
crop by its percentage of protein. The last two columns of 
the table show the percentages of the yields of dry matter and 
of protein for each section if the average of the yields from the 
mineral plots be taken as a basis (100). 
Protein. Proteid and non-protetd nitrogen.—It is customary 
to estimate the protein in plant tissues by multiplying the total 
nitrogen by the factor 6.25. The reason for this is that a 
large number of the compounds which are called albuminoids 
or proteids contain not far from 16 per cent. of nitrogen. But 
later research is emphasizing more and more clearly that (1) 
the true albuminoids or proteids which are used as food for 
building the nitrogenous tissues and other materials of the 
body often contain more and occasionally less than 16 per 
cent.; (2) in the growing parts of the plant especially, more 
or less of the nitrogen is in the form of so-called amids, like 
asparagin, which have not the nutritive value of the true 
albuminoids or proteids; and (3) in some cases a not inconsid- 
erable part of the nitrogen in the plant may be in the form of 
nitric acid, which has no value as food for animals. 
Unfortunately the chemical methods thus far devised for 
determining the amounts of amids and other like non-proteid 
or non-albuminoid nitrogenous compounds do not give satis- 
factory results. In making the analyses of the samples of 
these crops tests for nitrates were made in a considerable num- 
ber of samples, especially in those from sections of the plots 
upon which the larger quantities of nitrogen were used in the 
fertilizer. The object of these tests was to ascertain if any 
appreciable amount of the nitrogen of the fertilizer was taken 
up by the plant and held in its tissues in the form of nitrates 
without being transformed into organic nitrogen compounds. 
These nitrates would have no food value. The tests were 
made by treating cold water extracts of the samples with a 
sulphuric acid solution of di-phenylamin. Only very small 
traces of nitrates were found in any of the tests, indicating 
that practically all of the nitrogen of the fertilizer taken up 
by the plant was transformed into organic nitrogen com- 
pounds. | 
