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Use of the mouldboard plough
In modern use, the mouldboard plough was used for three reasons:-
- Foremost was the control of weeds. In this function, mouldboard ploughing is very successful, a farmer can control weed growth with far fewer herbicides by using this technique than is otherwise possible with any other method, aside from hand weeding, which is labour-intensive and not practical for large operations.
- To break up the soil for planting.
- To warm the soil for planting.
Only the first reason for mouldboard ploughing really paid off. Most plants require little soil agitation to germinate, so breaking up soil is unnecessary beyond what a planting implement accomplishes on its own. Soil warming is also unnecessary beyond two or three inches below the surface, therefore bringing black fresh soil which heats more quickly and more deeply after the final frost of the year in unneeded.
Problems with mouldboard ploughing
Mouldboard ploughing has become increasingly recognized as a highly destructive farming practice with the possibility of rapidly depleting soil resources. In the short term, however, it can be successful, hence the reason it was practised for such a long time. A field that is mouldboarded once will generally have an extraordinary one time yield as the larvae of pests and seed from weeds are buried too deeply to survive. After the first harvest, however, continued mouldboarding will diminish yields greatly.
The diminishing returns of mouldboard ploughing can be attributed to a number of side effects of the practice:-
- Foremost is the formation of hardpan, or the calcification of the sub layer of soil. In some areas, hardpan could once be found so thick it could not be broken up with a pickaxe. The only effective means of removing hardpan is using a "ripper", or chisel plow, which is pulled through the hardpan by an extremely powerful and costly tractor. Obviously, this layer eventually becomes impenetrable to the roots of plants and restricts growth and yields. This layer also becomes impenetrable to water, leading to flooding and the drowning of crops.
- Mouldboard ploughing rapidly depletes the organic matter content of soil and promotes erosion; these two problems go hand in hand. As soil is brought to the surface, the root structure of the previous harvest is broken up, and the natural adhesion of soil particles is also lost; though loose soil appears good for plant germination (and it is), this loose soil without cohesion is highly susceptible to erosion, multiplying the rate of erosion by several factors compared to a non-mouldboarded plot. This increased rate of erosion will not only outpace the rate of soil genesis but also the replacement rate for organics in the soil, thus depleting the soil more rapidly than normal.
- Mouldboard ploughing leads to increased soil compaction and loss of pore space within the soil. Soil is a bit like a bucket full of balls filled with sand. Each ball represents a cohesive particle of soil, and when stacked the balls leave a great deal of air space, required for healthy root growth and proper drainage. Mouldboarding so disturbs the soil that it breaks these balls and releases their contents. When this happens, the much smaller particles that are within the larger particles are released and pore space diminishes, leading to hard compacted soil that floods easily and restricts root growth.
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Horse-drawn plough.
A pair of metal wheels from a plough on a farm near Dordrecht, Eastern Cape. |
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Soil erosion
One negative effect of plowing is to dramatically increase the rate of soil erosion, both by wind and water, where soil is moved elsewhere on land or deposited in bodies of water, such as the oceans. Plowing is thought to be a contributing factor to the Dust Bowl in the US in the 1930s. Alternatives to plowing, such as the no till method, have the potential to limit damage while still allowing farming.
Plough parts
- Frame
- Frog
- Share (also called a plowshare or ploughshare)
- Mouldboard
- Runner
- Landside
- Shin
- Trashboard
- Handles
- Hitch
- Knife or coulter
On modern ploughs and some older ploughs, the mouldboard is separate from the share and runner, allowing these parts to be replaced without replacing the mouldboard. Abrasion eventually destroys all parts of a plough that contact the soil.
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