Studies in Prairie and Woodland 



35 



Soil Moisture 



Soil moisture determinations were made by means of a Briggs 

 geotome at somewhat irregular intervals from April 5 to Septem- 

 ber 22, 1 91 7. In taking samples in the shrub and especially in the 

 forest the practice was followed of removing the leaf mould 

 or dufif before inserting the soil tube. Samples to a depth of 5 

 feet were taken only four times during the season, those from 2 

 to 3 feet in depth somewhat oftener, while soil moisture in the 

 first 2 feet of soil, that portion which shows the greatest variation, 

 was determined 14 times during the growing season. These data 

 for prairie, shrub and woodland are shown in the following tables : 



TABLE 3 



The Available Water Content of the Soil in the Prairie, Shrub and 



Forest Communities at Depths of to 6 and 6 to 12 Inches 



at Peru in 1917 



An examination of table 3 reveals several interesting facts. It 

 may be seen that the wilting coefificient of the soil at depths of 

 0-6 and 6-12 inches respectively, increases progressively from 

 prairie to forest. This is undoubtedly due to the increase in the 

 humus content of the soil. Further it may be seen that the water 

 available for plant growth also increases as we go from prairie 

 through scrub to forest, and this notwithstanding the greater 

 progressive increase of non-available water. In other words the 

 water holding capacity of the humus enriched soil is increased 

 much more rapidly than its corresponding ability to withhold 

 water from the plant. Comparing the available water of grass- 



41 



