EXPERIMENTAL WORK WITH RAW ROCK PHOSPHATE. 63 
The results on corn given in Table XXXII are rather inconclusive, 
even though they represent the crops of six years. The average pro- 
duction of the no-phosphate plots was in many instances greater than 
‘that of the plots receiving phosphate treatments. Only in the cases 
of the plots treated with reverted phosphate of iron and aluminum 
were there fairly consistent increases obtained over the check plots. 
In 1903 the average yield of the check plots exceeded that of any of 
the others except the Florida soft phosphate plots and equaled the 
average yield of these. 
The yields of the various soluble phosphate plots were very incon- 
sistent. For instance, the plot treated with double acid phosphate 
gave on the average an increase in yield over and above the no- 
phosphate plots, yet the plot treated with dissolved South Carolina 
rock (ordinary acid phosphate), which was applied in such quan- 
tities as to furnish the same amount of phosphoric acid, gave a mel 
considerably below the average of the check plots. 
The results obtained on the hay crop (Table XX XIII), once 
were more consistent. With the exception of the first crop of the 
dissolved South Carolina rock plot, the yields from the less soluble 
phosphate plots were greater than from the water soluble phosphate 
plots, and in nearly every instance the yields of the treated plots 
were considerably greater than those of the checks. Here, again, 
the reverted phosphate of iron and aluminum gave the hivhest yields. 
Although the:conditions of this experiment were apparently more 
favorable to the soluble phosphates the results indicate that for corn 
and hay the relatively insoluble phosphates of iron and aluminum 
in a very finely divided or precipitated condition, were more effective 
than the former. 
In the case of the two crops of wheat grown on these same plots 
the opposite results were obtained (Table XX XIII). The yields 
of the soluble phosphate plots in most instances exceeded the yields 
of the relatively insoluble phosphate plots quite appreciably, and all 
the treated plots gave considerable increases in yield over the check 
plots. 
Regarding the influence of decaying organic matter in hesatl the 
turning under of rye seemed to increase somewhat the effectiveness 
of the insoluble phosphates, but the plots on which clover was grown 
and subsequently turned gave on the average smaller yields than 
similar plots receiving no organic matter. 
In studying the results of these experiments two questions natu- 
rally arise. First, how uniform was the soil of the various plots, 
and, second, what would have been the effect of applications of lime? 
Another five-year experiment undertaken by the Maryland station 
some time after the one just described and discussed, gives consider- 
ation to these points. In this later experiment an attempt was 
