62 
which was available also failed to correspond to the amount of any 
other constituent in the guano. 
Two hundred and twenty-two samples were analyzed for the fer- 
tilizing constituents only, the maximum percentages found in different 
samples being as follows: Total nitrogen, 13.04 per cent; nitrogen as 
ammonia, 3.60 per cent; nitrogen as nitrate, 4.60 per cent; total 
phosphoric acid, 41.58 per cent; water-soluble phosphoric acid, 2.39 
per cent; citrate-soluble phosphoric acid, 28.66 per cent; water- 
soluble potash, 4.18 per cent. Minimum percentages found in differ- 
ent samples were practically zero for each constituent. 
A number of samples were tested by vegetation experiments in 
pots for the immediate efficiency of their phosphoric acid in a neutral 
sandy soil. Calling the efficiency of the citrate-soluble phosphoric 
acid in acid phosphate 100, the efficiency of the phosphoric acid in 
different bat guanos varied between and 108. About half the 
samples tested had an availability of 20 or more, which compared 
well with bone meal under the same conditions, and in most the 
phosphoric acid was more available than in finely ground rock 
phosphate. 
The phosphoric acid of the guanos was equally available for corn 
and millet. 
Most guanos, in common with bone meal and floats, were far more 
effective in an acid red clay than in a sandy soil. Some guanos, 
however, were no more effective in the clay than in the sand. 
The efficiencies of nearly all guanos relative to acid phosphate were 
much greater when applied six weeks before planting than when 
applied immediately. This increased efficiency relative to acid phos- 
phate, was due to a depression in the availability of the acid phos- 
phate, as the guanos showed practically no absolute gain in efficiency 
by remaining in either the clay or the sand. 
Four of eleven guanos tested were unaffected in efficiency by liming 
the soil. The remaining guanos, with bone meal, floats, slag, and 
acid phosphate, suffered a moderate to extreme loss in availability 
from liming. 
As the efficiencies of the guanos appeared unaffected by the quan- 
tity used, they should produce maximum yields if applied in sufficient 
quantity. 
The phosphoric acid in guanos was as efficient during the early 
growth of corn and millet as during the later stages. 
In 70 per cent of the 92 samples tested there was fair to excellent 
agreement between efficiencies of phosphoric acid as determined by 
solubility in ammonium citrate and by vegetation experiments. With 
most of the samples where agreement was poor the citrate solubility 
was far higher than the vegetative efficiency. 
