Early Tillage to Conserve Moisture 149 



and 2.05 pounds for a clay loam, per day and per 

 square foot. 



As soon as the surface of the soil becomes air- dry, 

 the rate of evaporation from it is very much slower, 

 for in this condition it does not conduct the water 

 upward as rapidly as when nearly saturated. Early 

 tillage contributes to this end, and thus greatly di- 

 minishes the losses which would occur early in the 

 season. 



There is no tool made which produces a more 

 effective mulch than the common plow, which cuts off 

 completely a layer of soil of the depth desired and 

 lays it down bottom up in a loose, crumbled condition, 

 reducing the capillary conducting power to the mini- 

 mum. It is not possible, however, to use the plow as 

 early in the season as some of the other tools, like the 

 harrow ; neither is it possible to cover the ground as 

 rapidly with it. Further than this, it is often unde- 

 sirable to stir the soil as deep as it must be worked 

 with the plow, in order to make a good mulch ; and 

 so one or another form of harrow is used instead. 



When small grains are sowed on fall plowing, or 

 on corn or potato ground without plowing, it is 

 important to start the surf ace -working tools at the 

 very earliest possible moment, not simply to save 

 moisture by developing a mulch, but to aerate and 

 warm up the surface soil, so that the nitrates may 

 begin to be developed and placed in readiness for the 

 crop which is to follow. It is this saving of moisture, 

 and the early and abundant development of soluble 

 plant -food, which is invariably associated with and the 



