One of the most enduring symbols of modern agriculture is that of the moldboard plow. After all, this was the tool that turned under the perennial, native grass prairies of the Midwest and Great Plains so the ground could produce annual crops like corn and wheat instead. But even though it is such a time-honored symbol, the moldboard plow is a relative newcomer on the farming scene, having been impossible prior to the development of steel in the early 19th century. (Ed. note: The forked plow, however, dates back to Mesopotamia, before 3000 BC.)
Today the array of tillage implements is as diverse as the average fisherman's tackle box. There seems to be a tool for nearly every purpose, if not more. But let's sidestep the status quo for a moment and ask what it's all for.
Why tillage? I'm not asking this rhetorically. When answers to such questions seem glaringly obvious, it's wise to reflect on the words of Wendell Berry: "Seldom do we know what we're doing, because seldom do we know what we're undoing." Because tillage disrupts natural processes more than most agricultural practices, we need to carefully think about the purposes of tillage.
Very briefly, the main purposes of tillage are: 1) to prepare a suitable seedbed, 2) to eliminate competition from weed growth, and 3) to improve the physical condition of the soil. Within this third purpose, I would include the incorporation into the soil of compost, animal manures and/or crop residue. The best tillage system or systems to use must accomplish one or more of these purposes effectively and efficiently while improving the condition of the land.
Control of both wind and water erosion becomes a key consideration in deciding which system to apply. And in arid regions, you want to select tillage practices which conserve soil moisture to the greatest degree possible.
As a general rule, a desirable seedbed is one that is mellow, yet compact enough that the soil particles are in close contact with the seed. The seedbed should be free enough from crop residue that interference with the emerging seedlings is kept below a tolerable level. Furthermore, you want the soil to retain enough moisture to germinate the new seed and sustain plant growth. This last point obviously isn't so critical in areas which receive plenty of rain during the growing season or even where adequate irrigation water is always available.
It's all too common in many farming areas for people to practice "recreational tillage." In other words, more tillage is used than is necessary to accomplish the needed results. In fact, recreational tillage has done more to harm our soil base than anything short of regular soil fumigation. To avoid the short-term financial waste and long-term environmental waste of recreational tillage, always bear in mind the purposes of tillage, along with Wendell Berry's words.
Throughout the balance of this article we'll consider each purpose of tillage and the implements used to accomplish them. Furthermore, we'll look at the benefits and detriments of each practice. Keep in mind, though, that this is not a discussion of the principles and practices of tillage. The focus here is only on the equipment options.
Seedbed Preparation -- Primary Tillage
Moldboard plow: Since I've already mentioned it, let's start with the moldboard plow. As this implement is drawn through the soil, it shears off a "furrow slice" of soil and inverts it to one degree or another by means of a 3directional wedging action caused by the curved blade. The soil is broken into lumps and may even be pulverized to some degree, depending on the moisture content of the soil.
Not all moldboard plows are created equal, though. Large, breaker types with a long moldboard are designed to take out virgin or tough sods and completely invert them without breaking up the soil. On the other end of the spectrum is the stubble plow, which partially turns under grain stubble while pulverizing the soil.
The power requirements on moldboard plows can be high, though. For average depth stubble plowing (relatively light duty), about five drawbar horsepower are required of a tractor for each 14 inch bottom or blade of the plow. For deeper plowing, turning sod or using larger bottoms or blades, more horsepower per plow bottom is required. Heavier tractors in the 20 to 40 horsepower range can effectively pull up to a three-bottom plow for most purposes. Smaller tractors, like Kubotas for example, may have sufficient horsepower, but lack the weight and wheel diameter to effectively pull moldboard plows of anything but the smallest size.
In light of Wendell Berry's words, bear in mind that moldboard plowing "undoes" much. As a very disruptive form of tillage, it can be easily abused through overuse. Such a warning harkens back to the early 1940s when Edward H. Faulkner wrote Plowman's Folly.
I am of the conviction that there are only two contexts in which the use of a moldboard plow can be justified. The first is when a stand of native or perennial vegetation is to be "taken out" in order to put in another crop. If you are considering taking out a native meadow, give careful thought to the matter! Native meadows tend to have a high level of biological stability which will be dramatically reduced by turning it under with a plow. You may be much better off in the long-run to save that meadow for grazing livestock.
The other context in which the use of a moldboard plow can be justified is to mix (not invert!) crop residue, compost or livestock manure into the soil. (Inversion of the soil undoes the natural stratification or layering of beneficial microorganisms in the soil and actually hastens the disintegration of the soil. As one Native American said long ago as he observed the moldboard plow in action, "Wrong side up!")
Chisel Plow: In response to the erosion problems of the moldboard plow, the chisel plow was created in the 1930s. It tills as deep as 16 inches by lifting and loosening the soil without inverting soil layers. Consequently, it also leaves much more crop residue on the surface, providing additional protection against erosion. Perhaps its greatest benefit is that it provides the deep soil preparation without inverting the various layers of microbial populations. This leaves the soil in a more vigorous and vital condition.
The chisel plow amounts to a series of stout C-shaped shanks measuring about 2 inches wide and up to 24 inches from top to bottom. Different types of tips can be mounted on the ends of the shanks to modify the chiseling action.
Broadfork: For very small farms which are highly labor-intensive, the broadfork provides excellent deep soil preparation. Also called the U-bar, the broadfork resembles a large spading fork with two vertical handles. The fork is about two feet wide with stout teeth spaced every 4 inches or so. The teeth can be anywhere from 12 to 18 inches long. Some garden supply and tool businesses offer the broadfork for sale. Mine is a large, sturdy version custom-built by a friend and board member of The Center for Small Acreage Farming, Ken Backstrom.
To operate, the fork is held with the teeth vertical on the soil surface. This leaves the handles tilted slightly forward. As the operator steps on the cross bar, the teeth are pressed into the soil, sometimes with a slight lateral rocking motion for heavier soils. Then the operator leans the handles backward which brings the teeth up thus loosening the soil without inverting it. The fork is then placed 6 to 8 inches back and the procedure repeated.
I've used my broadfork a couple of years now and consider it a marvelous invention. Not only is it an effective way to prepare soil deeply, it also provides great exercise for the upper body. For operations less than an acre, the broadfork represents a good choice for deep tillage if you're in reasonably sound physical condition. Even with my recurring back problems, I consider the broadfork to be a valuable asset.
In the next issue, we'll explore tillage equipment further by looking at secondary tillage implements.
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:||part 3|
|Publication:||Countryside & Small Stock Journal|
|Date:||Sep 1, 1998|
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