WEDGING ACTION OF LAND IMPRINTERS
June 10, 2003
(Updated from 1 May 1991)
Robert M. Dixon, Ph.D
The standard rolling land imprinter has V-shaped teeth that open up imprints in the soil surface to hold important land resources in place such as plant litter, seed and rainwater. As an imprinter rolls along, the V-shaped teeth penetrate the soil surface, wedging soil forward, backward, and upward to form the imprints, without soil inversion. In contrast, the moldboard plow and share also wedges the soil during operation, but inverts it in the process, covering plant litter and not forming imprinted pockets to hold land resources. Thus, land imprinting is a form of conservation no-till that can form a seedbed in a once-over operation and conserve the resources needed for seed germination, seedling establishment and plant growth.
The wedging action of rolling land imprinters emboss or lift the soil surface several inches. Thus, the original soil surface is located about midway between the trough & crest of imprints. All tillage implements wedge the soil in one way or another, but the wedging action of land imprinters is unique because soil inversion does not occur. In hard soils this action can be aided by a gang of rolling coulters to pre-cut the soil at the ends of the imprints. These coulters should be designed to cut through plant trash or litter by having such features as fluting, waffling and notching. Using the coulter gang reduces the amount of imprinter ballast required for full penetration of imprinting teeth. The coulters not only cause less soil disturbance than ripping shanks, but cut through mats of heavy plant material that increase the load bearing capacity of the soil, sometimes preventing complete penetration of the imprinting teeth.
Imprinters can be hitched to tractors in a variety of ways including tow tongues for connecting to the tractor drawbar with a hitch pin, 3-point hydraulic hitching at the rear of most farm and industrial tractors, or they can be attached to dozer blades and front-end loaders. The latter two hitchings or attachments are appropriate for steep slopes. The tow-tongue hitched imprinter can be raised by hydraulic lifting wheels attached to the rear of the imprinter.
One of the best hitching methods has been an imprinter mounted at the rear of a 4-wheel drive farm or industrial tractor on the tractor's 3-point hitch. A front-end loader gives the tractor the needed extra traction and the bucket is handy for carrying extra bags of seed and inoculants. The overall width of the imprinter should not exceed 8 feet to obviate the need for a wide-load permit when hauling on the highway. Fortunately, the type of tractor just described-4-wheel drive with front-end loader and rear end 3-point hitch-are readily available on the farm and in rental yards with industrial equipment.
Besides tractor-operated rolling imprinters, there are 2 types of hand imprinters-the triangle and the blade, both of which are made from steel. The triangle types are specially fabricated for the wedging function of an imprinter, whereas the blade types are commercially available and designed for a use other than imprinting, but can also be used to wedge an imprint when operated in a slightly abnormal way.
The commercial blade-type hand imprinter also has 2 designs-one intended for use as a roofing spade and the other as a lawn edging tool, both of which are available at garden and hardware stores. The procedure for using these hand tools to make imprints varies slightly from the common method. The blades are forced into a moist soil surface with the foot placed upon the bar or stirrup provided and then the T-shaped handle is swung through a 30 to 60 degree angle at right angles to the blade to wedge or pry open the imprint.
Its important to keep the cutting edges of the triangles and blades sharp for easy and correct operation. Sharp cutting edges will slice through any plant residue on the soil surface before the blade penetrates the soil. Plant residue should be left on the soil surface with as little disturbance as possible to suppress raindrop impact, surface sealing, evaporation, and weed growth.
And finally it is important not to lift and invert any soil while making the imprints by hand. Such inversion is a soil disturbance that will reverse the natural plant succession rather than accelerate it. Weeds or early successional plants are favored by soil inversion. Most of the common methods for weed control involve soil inversion and thus are counter productive, producing more rather than less weeds in the long run. Plowing, disking, harrowing, and rototilling are common methods of tillage, all of which favor the germination and growth of pioneer plants or weeds. Even hand hoeing and pulling inverts some topsoil. The wedging action of land imprinters is superior to conventional tillage tools because the topsoil is not inverted and soil disturbance is minimal.