48 
that on phosphoric acid, as only 91 of the 247 samples contained 1 
per cent or more of total nitrogen. Moreover, in 22 of the 91 sam- 
ples 50 per cent or more of the total nitrogen was present as ammonia 
and nitrate, the availabilities of which are known. The object of 
the following tests was to determine the immediate efficiency of that 
part of the nitrogen which was not present in a form of known availa- 
bility. Therefore, as a rule, only samples were tested which had 
less than 50 per cent of the total nitrogen in the form of ammonia 
or nitrate. 
In four experiments dried blood (containing 14.33 per cent nitro- 
gen) was used as the standard for comparison, and in three experi- 
ments sodium nitrate was the standard. It seemed advisable to 
calculate all the results with sodium nitrate as a basis. In order to 
do this, a value of 71 was assumed for the efficiencies of blood relative 
to sodium nitrate in the last two tests. The value of 71 was assumed 
as being probable from the values actually determined in the other 
tests. The values for the guanos used in these two tests are conse- 
quently subject to doubt within narrow limits. 
Corn and millet were the crops grown. The river sand was used 
in two tests, the red clay in one test, and a mixture of nine parts 
red clay subsoil and one part sea sand (containing 19.4 per cent 
carbonate of lime) in three tests. To promote nitrification, slaked 
lime was incorporated in all soils except the subsoil mixture. 
In the three largest tests efficiencies were calculated from the quan- 
tity of nitrogen in the crop rather than from the mere weights of 
the crop. Efficiencies calculated from the analyses of the crop were 
in most cases practically the same as efficiencies calculated from the 
green weights. It was thought necessary to analyze the plants, as 
those receiving blood and some other materials were later in devel- 
oping and much greener than other plants. No such irregularities 
occurred in the phosphate experiments. 
Immediate efficiency of the nitrogen in guanos. — The tests described 
above and reported in detail in Table XX were conducted to deter- 
mine the efficiency of the nitrogen in guanos when applied immediately 
before planting a short-time crop. In this table the efficiencies of 
the nitrogen in guanos are expressed relative to the efficiency of 
nitrogen in sodium nitrate taken as 100. As all the nitrogen in 
sodium nitrate is available (although not recoverable in the crop), 
the figures for relative efficiency also express the percentage of the 
total nitrogen available under the conditions of the experiments. 
By comparing the figures for efficiency with the figures showing the 
percentage of the total nitrogen present as ammonia and nitrate, it 
can be seen to what extent the organic nitrogen is available. 1 
1 For this calculation it is considered safe to assume that ammoniacal nitrogen has the same availability 
as nitric nitrogen. 
