Moldboard window plow, evolution of a basic piece of equipment

The millennial history of the plow has not yet come to an end. Its evolution has led to the arrival of models of the moldboard window plow to combine performance at work and the reduction of energy requirements

Though we have downscaled the work of modern conservation agriculture techniques the plow is still the principal piece of equipment for primary soil preparation, especially in the Mediterranean region.

“Land is worked at the cost of fatigue.” This is not only a well known saying in the rural environment but a very real statement which becomes strongly evident in consideration of the energy, that is, the fuel consumption, needed for preparing a minimum tilling seedbed compared to the traditional plow-harrow combination.

The plow has been refined over the millennia and became increasingly widespread in the past century thanks to the available of tractors of greater power and strong traction capabilities to ensure efficient work on the land at greater depths.

For preparing the soil with the well known conservation farming technical regime plowing is undoubtedly the operation which requires the greatest energy. Other than breaking up clods and crust for pulverizing the soil — often after an opportune period when the soil worked is exposed to atmospheric agents — plowing at depth incorporates crop residues and drastically reduces weeds as well as rhizomes and seeds which are sent to the deepest layers of the soil where they are unable to surface.

At it is, by now most farms have moved to the stable use of conservation agriculture with zero, strip or minimum tillage and have recourse to the plow to deal with problems involving flora infestation and, more commonly, weeds.

A bit of history

The plow has a multi-millennia history dating back to 6000 BCE when domesticated oxen with sufficient traction ability became available for overturning the terrain to bring nutritional components to the surface to the benefit of raising wheat on the least fertile land. In the Middle Ages the plow evolved to become heavy with shares in iron and asymmetrical bottoms, mounted on wheels and capable of working the soil to substantial depths. In the first half of the 19th century, the first moldboards in iron made their appearance in Britain to clear the way to the manufacturing of these components. In the United States around 1830 a blacksmith with a name now known around the world, John Deere, invented a plow made out of highly polished steel and a correctly shaped moldboard, the self-scouring steel plow, which marked the step in the evolution of the implement valid to the present day. The thousands of years of the history of the plow should not be forgotten. Even today the support on which the various components of the plow are attached is named the bure with reference to the buoi (oxen) which first pulled the implement. 

 

The technique

The cut of worked plots of land is done with a horizontal blade, the plowshare, attached to the bottom is the moldboard or ear, which can rotate to a tilt of 135° from its original location. On the other hand, the vertical cut is the job of the coulter knife which works ahead of the plowshare to facilitate penetration of the terrain.

The technical evolution of the parts which cut the soil has been due substantially to improving resistance to wear and modifications of the moldboard have been considerable. At present, on offer on the market are moldboards with widely differing characteristics in performance.

The moldboard is normally made of three stacked layers of steel. The outside layers, upper and lower, are very hard and not very flexible but resist wear, whereas the inner layer is made of cold-rolled or mild steel which is much more ductile.

As regards shape, the moldboard surface is a continuous curve oriented toward the direction of advance which terminates with a transverse inclination of 35-45° for correctly overturning the section of soil cut by the courter and plowshare thanks to the dynamics of the plow and the soil.

The ratio of the slice cut and depth of plowing generally varies from 1 to 1.6 with the lowest values found for the deepest plowing.

For optimizing the efficiency in overturning and breaking up clods the curve of the surface should be continuously adapted to the conditions of the soil worked and forward speed. In fact, almost all manufacturers direct construction to three standard moldboard types, helicoidal, cylindrical and hyperbolic.

The most popular form in Italy is the helicoidal which is less aggressive in overturning the slice in spite of less efficiency in breaking up clods.

Though there are no sharp differences between various types, the length of the helicoidal moldboard is 3 or 3.5 times the width of the cut whereas the cylindrical type breaks up the soil with much greater energy with values down to 1.5-2.5 resulting in more mixing of the layer worked rather than a good and proper overturn.

 

The evolution of materials

Because wear is a plow’s worst enemy, research has been focused on innovative materials for the body as well as for coating the surfaces of the moldboard, also for reducing friction generated in sod breaking.

Plastic materials and Teflon have led to interesting results, especially for reducing traction force but overall, some difficulties have cropped up for reliability over time.

 

Window moldboards

Window or strip moldboards have been on the market for several years to reduce the   traction requirement by mounting a series of strong steel bars correctly spaced and in parallel to recreate the shape and extension of the single body.

Quality and thickness of the steel being equal, window moldboards feature longitudinal openings which reduce friction between the metal surface and the soil to reduce friction by 20% compared to traditional moldboards to lower tractor power proportionally.

Moreover, the lack of the continuity of the windows slightly increases the breakup of the clods turned up to save energy needed for successive operations for refining the soil.

The first window moldboards did not work well in harsh soil because stones and rocks clogged up the windows to only increase the friction of the component at work.

This problem was remedied more recently with the arrival of windows opening to the rear to help discharge stones to the rear of the component.

Another advantage of the window moldboard compared to the traditional one is that it is lightweight, a feature which facilitates transport.

 

The market

There are numerous small and medium-size companies in Italy specialized in the manufacture of plows — many them featuring extremely high quality — with 90% of production earmarked for export. Moreover, there is no lack of craft shops which are the only facilities for the fine tuning of particular products with capabilities to meet the requirements for demanding operations in cohesive soil.