EFFECT OF NITROGENOUS FERTILIZERS. 165 
Explanation of Tables 27, 28, 29, 30.— Tables 27 and 28 
show the analyses of samples of corn (grain) and stover re- 
spectively, taken in experiments extending over a period of 
nine years, although most of the experiments on a single field 
were not repeated more than once or twice. Two kinds of ex- 
periments were made; (1) soil tests, conducted primarily to 
study the deficiencies of soils in regard to the chief fertilizer 
ingredients; and (2) special nitrogen experiments conducted 
for the purpose of studying the effects of the nitrogenous fer- 
tilizers on the yield and the composition of the crop. In some 
cases the soil tests were a part of the special nitrogen experi- 
ments. In many of the soil tests samples for analysis have 
been taken, and the results averaged with those of the special 
nitrogen tests, from plots upon which the fertilizers applied 
were alike in kind and amount. (See plots A and 1, B and 2, 
Gand 7.) The percentages of food constituents in the corn and 
in the stover are calculated upon the basis of water-free sub- 
stance in the crop when it was harvested. The averages, given. 
in bold face type, are the values used in the summary Tables 12 
and 13, pages 136 and 138 in the discussion of results. 
Tables 29 and 30 give the total yields of water-free sub- 
stance and of the various food constituents in corn and stover 
from the same series of experiments. The amounts of water- 
free substance were determined by the weight of the corn and 
stover, and the percentage of water they contained, at the time 
when they were harvested. The amounts of food constituents 
were estimated from the water-free substance and composition 
shown by analyses. The averages given in bold face type in 
these tables are found in the summary Table 14, page 140 in 
the discussion. 
