182 Physics of the Soil. 



When ground is plowed late in the fall, just before 

 freezing, it then acts during the winter and early spring 

 as a mulch, diminishing the loss of water by surface evapo- 

 ration, and at the same time the roughened surface tends 

 to hold the snows and to permit winter and early spring 

 rains to penetrate more deeply into the soil, leaving the 

 ground more moist at seeding time than would be the case 

 if it were left unplowed. Determinations of the moisture 

 in the spring, as late as May 14, have proved that late fall 

 plowed ground may contain fully 6 pounds per square foot 

 more water in the upper four feet than similar adja- 

 cent ground not plowed. This difference represents a 

 rainfall of 1.15 inches and is a very important saving in 

 climates of deficient water supply for crops. 



212. Late Tillage for Orchards and Small Fruits. Late 

 fall plowing and deep cultivation in orchards of fruit 

 trees and in vineyards of small fruits, after the wood is 

 fully matured and growth arrested by the cold weather, 

 will do very much toward giving the soil better moisture 

 relations the next spring, tending to secure such results 

 as are cited in (211). In cases where injury from deep 

 freezing is liable to occur the late plowing will lessen this 

 danger because the loose soil blanket will help to retain 

 the heat in the ground as well as the soil moisture. 



In the late plowing and deep tillage, advised in this and 

 the last section, there is little danger of increasing the loss 

 of plant food by leaching because the season is too late 

 and the temperature of the soil too low to stimulate the 

 formation of nitrates. 



213. Early Fall Plowing to Save Soil Moisture. In those 

 cases where winter grain is to be sowed, the early plowing 

 of the ground, or plowing as soon as the field has been 

 freed from the preceding crop, is in the direction of econ- 

 omy of soil moisture. So too in sub-humid climates, even 

 where winter grain is not to be" sowed, it will often be 

 desirable to plow as early as possible in order to retain 



