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Tools for secondary tillage.

For as long as I can remember, I've enjoyed the sight, feel and smell of a mellow, healthy soil. Producing such a soil condition is the goal of secondary tillage. More specifically, secondary tillage takes the coarseness of soil subjected to deep, primary tillage and makes a smooth, weed-free seed-bed with soil particles fine enough to establish good contact with the soon-to-be-planted seed.

In this article, I will present some of the tools used in secondary tillage with a view to seed-bed preparation. There are plenty more tillage tools designed for cultivation (weed control) after the crop has been planted. Those will be presented in the next article in this series.

Disk Harrows

Disk harrows are one of the most versatile field tools of any kind on a farm. (A much larger version of this tool is the disk plow intended for primary tillage, but its use has declined considerably.) Disk harrows fall into two classifications: tandem and offset. The disks in both types are concave shaped plates which cut into the soil, lifting, turning and mixing the soil as it is pulled through the field.

In a tandem disk, two groups or gangs of disks are arranged in somewhat of a v-shape followed by two more gangs arranged in an opposite v-shape. The disk blades are normally 16 to 18 inches in diameter and are set about 7 inches apart. Most tandem disks are constructed with a rigid frame work which works well in loamy soils. Some tandem disks, especially older models, have a "floating" framework which is better suited to stony fields.

An offset disk resembles a tandem disk cut in half from front to back. The forward gang of disks is set at an angle which is a mirror image of the trailing gang of disks. Usually, offset disk harrows have larger disks, up to 20 to 24 inches in diameter, set on a spacing of 9 inches. Obviously, this one is designed for heavier duty work.

The angles in both types of disk harrows can be adjusted to regulate the cutting depth and mixing action. The sharper the angle between front and trailing gangs, the deeper the disk will cut. If front and trailing gangs are parallel to each other (perpendicular to the line of travel), the cutting and turning action is very light.

Spike-tooth Harrows

The spike-tooth harrow is one or more gangs of steel spikes fastened in a series of rows. New spikes are usually about 8 inches in length and have a diamond-shaped rather than round cross-section. A single gang is about 5 feet wide. Depending on your tractor's pulling capacity and tillage needs, you may pull from one to as many as 10 gangs at a time. Obviously, a 50-foot-wide harrow finds itself at home on a large-scale grain operation rather than a small-scale farm.

The spike-tooth harrow is designed to break down large soil clods and to level the ground to a limited degree. The depth of penetration can be altered by the angle of the teeth to the ground. The more vertical the teeth, the deeper they harrow.

Another use of the spike-tooth harrow is to set the teeth at a shallow angle and lightly harrow in seed that was broadcast on the surface. This is especially applicable for cover crops, green manures and pastures.

Spring-tooth Harrows

These harrows are a series of flexible C-shaped iron teeth arranged in patterns similar to the spike tooth harrows. Because the teeth are so broad and flexible, they do not perform as aggressively as the other harrows, which can be an advantage in stony ground. For the purposes of secondary tillage though, the spring-tooth harrow has been eclipsed by the more effective disk and spike-tooth harrows.

Though much less versatile than the previous harrows, the spring-tooth still has two helpful applications. t can be used to dig out roots of quackgrass and other weeds. Also, the flexible teeth make it a good candidate for cultivating alfalfa, as it can dig up weeds without damaging the alfalfa crowns as badly as any other kind of harrow would.

Due to their limited usefulness, you should be able to find one of these in a scrap pile on some farms. But don't bother bringing it to your place (even if it is free) unless you know you'll use it.

S-tine Cultivators

A more modern, vigorous and versatile version of the spring-tooth harrow is the S-tine cultivator. This cultivator can be mounted to the 3-point hitch or used in a hydraulically operated trailing version. The teeth of the S-tine are narrower and sturdier than the teeth of a spring-tooth harrow. It can work at depths similar to a disk harrow but does not turn, pulverize or mix the soil to as great a degree.

Corrugated Rollers and Cultipackers

Many fine-seeded crops such as alfalfa and many of the vegetables need a firm seedbed to ensure a good contact between the seed and the soil. In this case, you need to use a roller. Two common varieties are the corrugated roller and the cultipacker. The corrugated roller comes in varying widths and is basically a heavy rolling tube with ridges every 5 or 6 inches. The ridges break up clods as the roller packs the soil.

The cultipacker is similar except that in place of one continuous roller, there is a series of compacting sprockets or packing wheels each with a solid or toothed ridge. The cultipacker tends to leave a more even surface than the sharply ridged corrugated roller.

Rototillers, Vertical Tine Tillers and Spading Machines

Rototillers are understandably popular on everything from small gardens of several hundred square feet on up to small farms with several acres in production. Every model from the front-tine shoulder beaters to the large rear-tine varieties find useful applications in soil preparation. With just one pass, you can dig and pulverize soil and mix in compost and plant residue.

But a caveat is in order. Rototillers are hard on most soils, especially if used every year. In addition to chopping up much of your indispensable earthworm population, rototillers hasten the breakdown of organic matter by exposing so much soil to oxygen and light. Oxidation (chemical breakdown of materials in the presence of oxygen) occurs so rapidly in response to rototilling that it is simply not sustainable on an annual basis unless you are incorporating vast quantities of organic matter. Furthermore, fine soils with high silt or clay content will compact under the beating action of rototiller tines. While the tines are supposed to cut through the soil, the cutting action soon turns to a beating action as the tines dull with wear. So what's a person to do?

Two similar, and gentler options are available. The first is a vertical tine tiller which is a series of rotating pairs of vertical tines which mix the soil somewhat like a kitchen mixer combines ingredients. This tiller avoids the compaction problems of the rototiller and minimizes oxidation losses because it does not expose new soil to the surface. The 1938 USDA Yearbook of Agriculture speaks of such a machine being in use at that time. Now, however, we have to import these machines from Europe. The Lely Corporation in Wilson, North Carolina sells these tillers in the United States.

Another option is the articulating spader. This is truly an amazing machine which can attach to a BCS walking tractor or, in larger sizes, attach to the 3-point hitch of most tractors. At first glance, it resembles a rototiller. But instead of rotary tines, a series of spades cuts into the soil with a double-digging action. Clods are broken down as the spades throw the soil against the frame. This prepares the soil well without the compaction of a rototiller. While soil oxidation losses are higher than when a vertical tine tiller is used, the losses are lower than those caused by a rototiller.

Hand Rakes and Spading Forks

For biointensive mini-farming with raised bed production, secondary tillage is accomplished by means of hand rakes and spading forks. Granted, such farming is extremely labor-intensive, but it boasts two advantages which no other production system can claim. First, it is easier on the soil than any of the more mechanized methods, escaping entirely the compaction caused by machinery travel. Second, it also holds the title for being the least expensive method in terms of capital outlay. For very small farms (mini-farms) with adequate labor available, this method is not only economically viable, but often superior to the alternatives.

As with all tillage tools from large plows for primary tillage on down to the hand rakes and spading forks, best results are achieved by working the soil at the proper moisture content. Even with these hand tools, you can damage the soil if you work it when it's too wet. The soil should have good moisture content, yet crumble easily. In using the spading fork, the soil should be of a consistency that you can lift a spadeful of soil, yet have it crumble easily when you bounce that spadeful on the fork a couple of times with a rapid jerking motion. The rake will often break the soil even finer as you use it to smooth and level the planting surface on your raised beds.

Jeff and his wife, Carol, juggle equipment decisions on their small farm in Idaho.

Jeff also directs The Center for Small Acreage Farming which publishes a monthly newsletter and workbooks for small acreage farmers.

For a free brochure, write to: The Center for Small Acreage Farming, P.O. Box 219D, Fairfield, ID 83327.
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Title Annotation:seed-bed preparation
Author:Rast, Jeff
Publication:Countryside & Small Stock Journal
Date:Nov 1, 1998
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