July a8,19*3 
Efficiency of Phosphatic Fertilizer 
189 
efficiency of that which was applied immediately before planting was 
done. 
It should be borne in mind that the losses represented in the curve and 
in the foregoing tables were in excess of those sustained by acid phos¬ 
phate applied immediately before planting. Since the plants could not 
have utilized any appreciable quantities of phosphoric acid during the 
first 10 to 20 days after they were planted, it is evident that very con¬ 
siderable losses in the efficiencies of the phosphates probably occurred 
which are not shown in the experimental results. An idea of what these 
losses were can be obtained by extrapolating the curve beyond its origin 
to show what the efficiency of acid phosphate would have been had the 
phosphate been incorporated with the soil the day plants were ready to 
use it. 
NUMBER QfMY5~APPL/CAT/0A/ Of PEO$P//f)rE E/ZECEOED ElA/Vf/APO 
Fig. i.—E fficiency of acid phosphate as affected by time of application. 
These experiments do not show what loss in efficiency might be sus¬ 
tained by the phosphates after they had been used on these soils for a 
series of years. One is inclined to think that repeated applications of 
phosphates would bring about such conditions in a soil that succeeding 
applications would sustain smaller losses in efficiency on remaining in the 
soil. The results of long-continued plot experiments, however, do not 
for the most part support this view, since the later applications of phos¬ 
phatic materials in these experiments do not seem to be relatively more 
efficient than the earlier ones. 
The losses in efficiency established in these experiments for phosphates 
which remained a short time in unplanted soils, are greater than are 
usually conceived as taking place. In experiments by Schneidewind 
(25, 26) on a loess soil and a red sandy soil basic slag and acid phosphate 
apparently lost nothing in efficiency by remaining in the soil. There has 
been very little experimentation along this line, however. Determina- 
