Ig11] BRIGGS & SHANTZ—SOIL MOISTURE 217 
tion of the wilting point. Plants often wilt down during the day 
and recover during the night. The wilting of a plant in the hot 
part of the day is therefore no indication that moisture is not avail- 
able. We have consequently considered a wilted condition in the 
morning as proof that the moisture content had been reduced to 
the point of non-availability. Check determinations were repeat- 
TABLE I 
INDIVIDUAL POT MEASUREMENTS OF NON-AVAILABLE MOISTURE FOR KUBANKA 
WHEAT IN THREE SOIL TYPES 
Fine sand Fine sandy loam Clay loam 
per cent per cent per cent 
an 
a 
an 
© 
NDHHNYNHNNNHNHKHNNHHNHDN 
NTT Aa DUN Dat st DOr 
Lal 
OD PIWwW ORW ART HOWNAT: = 
f=) 
ie) 
ee ee 2.59 
Probable error of mean...._._ +=0.03 
Probable error of single observa- 
ee er ee +0. 11 +o0.18 0.34 
wm an 
~ 
an 
Ge 
a 
edly made by placing the pots containing wilted plants under a 
ll jar in nearly saturated air. These plants were unable to 
recover their turgidity. Since the wilting point is influenced to 
Some extent by the temperature and humidity of the air of the plant 
house, these conditions should be determined and kept as uniform 
48 possible during the growth of the plants. 
The degree of accuracy which may reasonably be expected by 
the wax seal method is shown by the series of determinations made 
with Kubanka wheat shown in table I, which gives the percent- 
@ge of non-available moisture found in each pot for three types 
of soil. The plants were grown in an ordinary plant house. The 
average temperature was about 70° F., and the relative humidity 
‘ 
