Conserving Soil Moisture. 183 



soil moisture and to facilitate the entrance of the fall rains 

 more deeply into the ground. The early plowing or disk- 

 ing in these cases may also be helpful in hastening nitrifi- 

 cation in the soil. 



It is the strong tendency of early fall plowing, in cli- 

 mates where there is plenty of soil moisture to develop 

 nitrates and where there is much rain in the late fall and 

 early spring, Which has led to the sowing of "cover crops" 

 having for their primary object the locking up of the solu- 

 ble plant foods to prevent them from being lost by soil 

 leaching; and the tendency of early fall plowing to dimin- 

 ish surface evaporation and thus, in wet climates, to in- 

 crease percolation and the loss of plant food may some- 

 times make this practice undesirable in such cases. 



214. Early Spring Plowing to Save Soil Moisture. In all 



climates where there is a tendency of the soil to become 

 too dry the earliest stirring in the spring, which is prac- 

 ticable without injuring the soil texture, is in the direc- 

 tion of economy in most cases because, at this season of the 

 year, the effectiveness of tillage in conserving soil moisture 

 is greater than at almost any other time. This statement 

 follows from (198), where it is shown that a wet soil car- 

 ries water to the surface much more rapidly and from a 

 greater depth than a dry soil can. In the spring the soil 

 at the surface is usually not only wet but also well com- 

 pacted, two of the most important conditions for the rapid 

 movement of water to the surface, and it is because of 

 these that early and deep sjfring tillage is so important 

 as a means of saving soil moisture. 



In one instance, where two immediately adjacent pieces 

 of ground, in every way alike, were plowed in the spring, 

 7 days apart, it was found that the earliest plowed ground 

 contained, at the time the second piece was plowed, a lit- 

 tle more moisture in the upper four feet than it had 7 days 

 before, while the ground which had not been plowed had 

 lost, in the same interval of time, an amount of moisture 

 from the surface four feet equal to 1.Y5 inches, a full 



