Plowing, or primary tillage, is the initial mechanical manipulation of soil necessary to prepare a field for planting. This process involves lifting, cutting, and inverting the soil layer, typically between six and twelve inches deep. The main goals are to bury previous crop residues and weeds, incorporate organic matter, and loosen the soil structure. This improves aeration and water infiltration, setting the stage for a productive growing season.
Assessing the Field and Soil Conditions
Before any equipment enters the field, assessing the soil’s moisture content is crucial, as working soil that is too wet or too dry can cause structural damage. The simple “ball test” provides a reliable field check: excavate a handful of soil from the intended plowing depth (six to eight inches) and firmly squeeze it into a ball.
If the soil is too wet, it will smear or form a tight ribbon, indicating a “plastic state” where tillage causes severe compaction. If the soil is too dry, it will crumble immediately, meaning the plow will struggle to penetrate and may create overly large clods. The ideal moisture level, known as the friable state, allows the squeezed ball to hold its shape but easily breaks apart into smaller pieces.
The timing of plowing often depends on the region and crop. Many farmers opt for fall plowing to allow winter freeze-thaw cycles to break up large clods, though spring plowing is necessary in areas with high erosion risk or poorly drained soil. The field must be cleared of large obstacles like stones, woody debris, or old root crowns prior to starting. Ignoring this debris can damage the plow’s components and lead to costly downtime.
Selecting and Setting Up the Plowing Equipment
For primary tillage, the two most common implements are the moldboard plow and the disc plow, each suited to different field conditions. The moldboard plow uses a curved metal bottom to slice, lift, and invert the furrow slice, effectively burying almost all surface residue and weeds. This plow is best used in soft, stone-free, loamy soils where a clean surface is desired, but it requires more horsepower than a disc plow.
The disc plow uses a series of large, concave, revolving steel discs to cut and mix the soil, leaving some residue on the surface. It is the preferred choice for hard, dry, rocky, or sticky clay soils because the rolling action handles obstructions and fibrous growth readily, minimizing clogging.
The plow size must be matched to the tractor’s horsepower (HP) for consistent depth and speed. Once hitched to the tractor’s three-point linkage, the plow requires careful leveling adjustments. Plowing depth is typically set at about half the width of the plow bottom; for example, a 14-inch bottom should run about seven inches deep.
The plow must be leveled both side-to-side and front-to-back while operating. Side-to-side leveling uses the adjustable lift link, ensuring the plow’s frame is parallel to the ground when the tractor’s right wheel is running in the previous furrow. Front-to-back pitch is controlled by the top link of the three-point hitch. Correct pitch ensures the entire length of the plow bottom is working the soil, with the share point slightly lower than the heel.
Step-by-Step Guide to Initial Plowing
Plowing begins with establishing the first cut, which determines the pattern for the entire field. A common method is the “back furrow,” starting near the center and throwing soil slices toward the middle to create a raised ridge. The operator continues plowing outward in concentric passes, always throwing the soil in the same direction.
Alternatively, starting at the outside edge and plowing inward creates a trench (“dead furrow”) where the final two passes meet. Maintaining a straight line is crucial for minimizing effort and ensuring a uniform surface. The operator should look well ahead, focusing on a distant marker rather than the immediate ground in front of the tractor.
A proper overlap is necessary on each pass, ensuring the front plow bottom cuts the full width of the unplowed ground up to the previous furrow. If the overlap is too narrow, an unplowed strip will be left. Too wide an overlap strains the tractor and leaves an uneven surface.
At the end of the field, a designated turning area, or headland, must be left unplowed. This area should be wide enough for the tractor to comfortably turn around, often six meters. When reaching the headland, the operator simultaneously raises the plow while turning the tractor to begin the return pass. The headland is only plowed after the main body of the field is complete, usually by plowing around the perimeter.
Consistent depth must be maintained throughout the field using the tractor’s draft control or depth stops, as variations affect soil inversion and the final surface level.
Next Steps After Plowing: Secondary Tillage
Primary plowing, especially with a moldboard plow, leaves the field surface rough, uneven, and covered with large clods. This condition is not suitable for planting, as most crops require a finer growing medium. Secondary tillage is necessary immediately following plowing to refine the seedbed.
Secondary tillage, such as disking, harrowing, or cultivating, is shallower than plowing, focusing on the top few inches of the soil. The main purpose is to break down large clods into smaller particles, level the surface, and control weeds brought up during plowing. Equipment like a tandem disc harrow or a field cultivator is used to achieve the required fine tilth, creating an optimal environment for seed germination and root development.