IOWA ACADEMY OF SCIENCES. 
63 
are in the ratio 1:1.36. The average percentage of potash 
dissolved by citric acid from the eight plots receiving no potash 
was .0038; while from the eight plots that had received potash, 
it was .0348. These figures are in the ratio 1 : 9. Again, an 
“overwhelming” difference. 
The results of Dyer’s work upon the Rothamsted soils, the 
treatment of which had been such as would naturally cause wide 
differences in the amounts of available plant food present, sug- 
gested the desirability of trying his method upon soils whose 
treatment had been that of ordinary agricultural practice. 
Therefore I resolved to try the method upon some samples of 
Iowa soils that I had in process of analysis last spring for the 
state geological survey; and I also resolved to apply the method 
to the nitrogen of the soils, as well as to the phosphoric acid 
and potash. 
Correspondents in different parts of the state had each sent 
me two samples of soil, one representing the “best” and the 
other the “poorest” soil occurring over any considerable area 
in his vicinity. Each sample was (or according to directions was 
to be) a composite sample from five different spots in the field or 
area which it was intended to represent. The directions were 
that every sample should be taken to a depth of exactly nine 
inches. The methods of Dyer were followed except in some 
details of the determinations, where the official methods of the 
Association of Agricultural Chemists were preferred. 
With these explanations the table of results will be intelligi- 
ble. (Table II.) The total nitrogen, also potash and phospho- 
ric acid soluble in hot HCl (1 e . , by the Association method) have 
been determined on eight samples, and for comparison these 
results are included in the table. 
