TILLAGE 343 



plowing should follow the preceding crop as soon as possible. The 

 primary object to be accomplished is conservation of moisture. In 

 humid regions the time of plowing depends upon the crop to some 

 extent: The plowing for wheat and rye must he done in summer, 

 while for corn, cotton, oats, barley, cowpeas, and soybeans it may 

 he done either in fall or spring. 



(a) Fall Plowing. If the plowing is done in the fall the 

 ground should be plowed as late as possible unless a catch crop is 

 planted to conserve the available nitrates. When the ground is 

 stirred by the plow it produces conditions very favorable for nitrifi- 

 cation, which takes place at the expense of the organic matter in the 

 soil, resulting in the production of soluble plant food that may be 

 leached out of the soil during the winter and spring. If a catch 

 crop is grown the plants take up the soluble plant food and preserve 

 it. In the case of very late fall plowing the conditions are usually 

 not favorable for any large amount of nitrification, and the result is 

 that little soluble plant food will be formed before winter. 



The soil never becomes too dry to be plowed in the fall when 

 looked at from the standpoint of benefit to the soil. It may become 

 so dry, however, that it will be impossible from a power standpoint 

 to do the work with horses. The tractor may be used to good advan- 

 tage under these conditions. 



There are several important advantages in fall plowing: first, the 

 work may be done at the time of the year when other work is less 

 pressing; second, the organic matter turned under during the fall 

 has sufficient time to partly decay before the crop is put in, thus 

 liberating the plant food and giving the soil time to settle and re- 

 establish capillary connection; third, many insects and their eggs 

 are destroyed by disturbing them late in the fall, which is especially 

 true of the ant hills containing the eggs of the corn root aphis; 

 fourth, the improvement of the tilth of the soil by exposing it to 

 freezing and thawing and wetting and drying during winter and 

 spring, producing a granular condition that is very desirable. This 

 is especially true of heavy soils containing a fair supply of organic 

 matter. 



As a general rule, soils deficient in organic matter do not re- 

 ceive as much benefit from fall plowing as soils well supplied with 

 this constituent. 1 1' deficient in organic matter, free/ing and thaw- 

 ing cause the soil to run together instead of producing granula- 

 tion. Timber soils generally are not as well adapted to fall plow- 



