THE PROBLEM OF TILLAGE 



of the seed. In fact it may be a fairly 

 long time before such raw land becomes 

 transformed into a mellow seed-bed. But 

 this seldom occurs in dry-farming, as the 

 summer fallow affords ample time for the 

 weathering of the ground, and so the soil 

 is generally well aerated before the crop 

 is planted. If the land is plowed year 

 after year at the same depth the sole of 

 the furrow becomes packed by the 

 smoothing action of the bottom of the 

 plow, as well as by the tramping of the 

 horses. This results in the formation of 

 what is commonly known as a hard pan 

 or plow-sole. A hard pan is injurious for 

 three reasons : it decreases the water-hold- 

 ing capacity of the soil; retards the 

 growth of the roots ; and checks the capil- 

 lary rise of moisture from the deeper 

 layers below. It is thus a sound plan to 

 vary the depth of plowing every two or 

 three years. Another point worth noting 

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