PHYSICAL PROPERTIES OF SOILS 4! 



Soils which are improved by rolling are not improved 

 by subsoiling. The additional expense involved should 

 be considered when subsoiling is to be resorted to. Ex- 

 periments have not as yet been sufficiently decisive to indi- 

 cate all of the conditions most favorable for this practice. 



32. Fall Plowing followed by surface cultivation con- 

 serves the soil water, by checking evaporation and leav- 

 ing the lanci in better condition to retain moisture. If 

 conditions allow, fall plowing can be followed by surface 

 cultivation, but in some localities heavy winds prevent 

 this. It is generally better to give the surface cultiva- 

 tion early the following spring. Clay land should be 

 left in a ridged condition when fall plowed, so as to ex- 

 pose a greater surface area and to allow a better oppor- 

 tunity for the water to sink into the subsoil. Evaporation 

 may take place from unplowed land during the fall, and 

 in the spring the soil contain appreciably less water than 

 plowed land. By fall plowing it is possible to carry over 

 a water balance of 100 tons or more from one year to 

 the next. 



33. Spring Plowing. When land is plowed late in 

 the spring there has been a loss of water by evapora- 

 tion, and the soil has not been able to store up as much 

 of the rain and snow as if fall plowing had been prac- 

 ticed. 15 Then, too, dry soil is plowed under and moist 

 soil brought to the surface, and if surface cultivation does 

 not follow, this moisture is readily lost by evaporation, 



