PHYSICAL PROPERTIES OF SOILS 



45 



However, the beneficial effect of these upon the moisture 

 content of soils is liable to be overestimated, because 

 the fertilizer undergoes fixation when applied, and does 

 not remain in a soluble condition. Fertilizers containing 

 soluble salts exercise a favorable influence upon the 

 moisture content of soils, but the extent of this influence 

 has never been determined under field conditions. 



38. Farm Manures. Farm manures exercise a bene- 

 ficial effect upon the moisture content of soils. When 

 the manure is worked into a soil, the coarse soil particles 

 and masses bind 

 together, and the 

 non-capillary 

 spaces are made 

 capillary. Free 

 circulation of the 

 air, which in- 

 creases evapora- 



, FIG. 18. Sandy Soil with Manure. 



tion, is prevented 



when a sandy soil is manured. When soils are manured 

 they retain more water, as shown by the following 

 example : M 



