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Plowing. Ordinarily the firs operation in fitting a seedbed is plowing although there are circumstances under which plowing may be dispensed with. Where the land is in sod or where considerable vegetation, dead or alive, is on the surface , plowing is essential, for incorporates this material with the soil where it is broken down by bacterial action until it becomes an integral part of the soil. Hard soils must be broken up, loosened, and aerated; plowing accomplishes this. Not only does the curved moldboard tend to crumble the soil as it is sheared off into a furrow slice, but it tips the soil over, facilitating the coverage of trash.
Several attachments aid in trash coverage. The rolling coulter and the jointer used on the plow beam cut the edge of the furrow cleanly and work trash toward or into the furrow where it is more readily covered. If the material to be covered is bulky, trash guards or wires can be used to drag it to the furrow and hold it there until it is covered by the furrow slice as the plow moves along. The wider plows are more effective in covering heavy trash. The disk plow is used in dry, hard soils, in sticky soils in which moldboards do not readily scour, or on new land with its roots and bushes. The action of the disk plow is similar to that of the disk harrow; but the disks are larger in diameter, ranging up to 30 in, and thus they can be set for deep as well as for ordinary work. On dry land, complete coverage of straw may not be desirable. If a considerable amount of this material is merely partly worked into the surface, it tends to reduce blowing.
Middle bosters and listers have the appearance of two plows, one righthanded and the other left-handed, set back to back. They are used largely in semiarid regions for the preparation of beds and ridges to hold moisture and reduce wind erosion. Corn, the grain sorghums, and wheat may be drilled in the furrow left by a lister-planter combination.
Tine of Plowing. The proper time to plow is not strictly an agronomic consideration. In many instances the chief factor may be distribution of labor.
However, fall plowing, under some conditions, has other definite benefits. In heavy gumbolike soils, spring plowing, at least for crops that are planted relativelay early, is often next to impossible. If such soils are plowed in the fall, time is saved and the freezing and thawing of winter and spring bring about a more granular condition, especially in the presence of a reasonable content of organic matter. On the heavier soil types, plowing or otherwise tilling the land when it is too wet may ruin the physical condition of the soil for several seasons. Wet, heavy soils are packed or puddle by tillage operations and upon drying are cemented into dense lumps almost as hard as a brick. These can be broken up and got into condition for proper aeration and moisture retention only after much time and tillage effort. This undesirable condition is most often brought about by spring plowing, but the tillage of heavy soils when they are wet should be avoided in any season. Sandy soils are not similarly affected.
When a tough, heavy grass sod is to be plowed for a spring – planted crop, it s effective decomposition is hastened by fall plowing. Furthermore the settling that occurs during the winter helps eliminate air pockets. A plowed surface left in the rough over winter is more receptive of moisture from rains and snows. The first spring tillage on fall-plowed land hastens drying of the surface and often permits earlier planting than is possible if spring tillage must await the drying out of the land until conditions are suitable for spring plowing.
Fall plowing is not suitable for rolling land subject to erosion. If such land is left without vegetation over winter, excessive washing and gullying often take place , especially if the land is deficient in organic matter. Sandy soils if fallplowed may be injured by wind erosion whether the land is sloping or level. Such lands are to be examined before cultivating.
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