474 
Journal of Agricultural Research 
Vol. XIV, No. II 
moisture becomes practically negligible when the ratio has been reduced 
to 2.0. 
In the case of the fields involved in the present study, the effect of 
evaporation in reducing the ration below 2.0 appears to have been con¬ 
fined to the surface 3 inches in the fallow and exposed subsoil and to a 
shallower layer in the grass fields, and, during August, in the cornfield. 
RELATION OP MINIMUM MOISTURE CONTENT TO WILTING COEFFICIENT 
AND HYGROSCOPIC COEFFICIENT 
The wilting coefficient as defined by Briggs and Shantz corresponds to 
the ratio 1.47 (6, p. 65). In the cornfield during the month of August 
ratios lower than this were not found, although throughout the season as 
a whole the moisture supply of soil and subsoil together had been ab¬ 
normally low, as evidenced by the yield of only 6 tons per acre of silage^ 
and by the data in Table XII. From this it would appear that in the 
surface foot of cornfields at Lincoln we would rarely find growth water 
absent, even in seasons of drouth, and that in the case of the com crop 
a statement of the amount of growth water would have more significance 
than that of free water. In the grass fields, on the other hand, while the 
free water at no time fell below about 2 per cent, the growth water was 
distinctly below zero on various occasions, and toward the end of July 
this dry condition persisted in the lower 6-inch section for at least a 
fortnight. The method of expressing the moisture conditions used 
above appears to us to have all the advantages of both of these as well as 
some possessed by neither. 
RELATION OF MOISTURE RETENTIVENESS TO CONTENT OF ORGANIC MATTER 
In both fallow and grass fields the highest ratios were observed in the 
surface 7 inches where the proportion of organic matter was highest, 
and in both these soon after heavy rains. In the eleventh- and twelfth- 
inch sections the maximums were below 3.0, thus approaching those in 
the exposed subsoil. The minimums were to be expected near the 
surface, but a ratio lower than 1.0 was observed only in the first inch, 
and this only on May 25. In the fallow the minimum ratio below the 
fourth inch varied between only 2.3 and 3.0, while for the different 
levels below the first inch in the grass fields it varied between only 1.1 
and 1.3, the lower 3-inch sections showing the lowest values. 
In the exposed subsoil, almost entirely lacking organic matter, the 
maximums were much lower. A ratio of 2.0 to 2.2 seems the highest 
to be expected in this after it has had a few days in which to lose by 
seepage the excess of water added by rain. Accordingly, ratios of 0.5 
to 0.7 and 1.0 to 1.2 would indicate the proportion of growth water and 
free water, respectively, retained in the exposed subsoil as contrasted 
with 0.9 to 1.5 and 1.4 to 2.0 in the fields with an ordinary surface soil, 
rich in organic matter. The same results have been obtained in labora- 
