FERTILITY AND HUMUS IN DRY AREAS 417 



the proper time adds greatly to the productiveness of 

 soils in dry areas. 



The benefits from humus. Prominent among the 

 benefits from the application of organic matter to the 

 soil are: (1) that it improves the physical structure of 

 soils; (2) that it adds to their moisture-holding power; 

 (3) that it furnishes food to plants in a readily available 

 form, and (4) that it lessens the lifting of soil by winds. 



Organic matter improves the physical texture of 

 soils by preventing them from lying too compactly. The 

 evils resulting from over-impaction are: (1) the bak- 

 ing of soils, which is adverse to aeration and to the 

 entrance of rain into the soil when it falls; (2) adding 

 greatly to the labor of tillage, and (3) it is proportion- 

 ally adverse to successful growth in the crops. When 

 the organic matter in soils is practically exhausted, 

 which is certain to follow long-continued cropping with 

 small grains, soils run together and become impacted in 

 many instances. There is virtually no organic matter 

 between the soil particles to keep them asunder. This 

 adhesive condition prevents the rain that falls in the 

 form of heavy showers from entering the soil as it other- 

 wise would, and because of this much of the moisture 

 that falls may run away over the surface and be lost 

 to the soil. That the soil may be kept in such physical 

 condition that the moisture that falls shall have an op- 

 portunity to enter the soil to the greatest extent possible 

 is greatly important in dry areas, and indeed in all 

 areas. The baking of the soil proportionally excludes 

 air, and as it does, it proportionally lessens the activity 

 of bacterial life, thus reducing the beneficent influences 

 that flow therefrom. The difference in the labor in- 

 volved in plowing a soil in a baked condition as com- 

 pared with the same in the unbaked form, will be read- 

 ily apparent, and the increased labor involved in the 

 pulverization of the same will be relatively greater than 



