Mexican Plow
Staff posted on October 24, 2006 |
Mexican Plow

Adapted from material by the Department of Philosophy and Department of Mechanical Engineering
Texas A&M University
NSF Grant Number DIR-9012252

A Challenge for Designers

There is a pressing need for a device to assist third-world peasant farmers in cultivating their small plots of land. This need has never been satisfactorily met by any of the plows currently available. This case involves the design of a plow that can fulfill this need.

The plow should be assisted in some way by a gasoline engine, but the precise nature of the assistance the engine will provide is a matter for the designer to determine. For example, the engine might be used to pull the plow, but it might also be used to vibrate the plow, making it less difficult for animals to pull the plow. Other ways of using the power from the gasoline engine may be possible. Although the plow would probably be appropriate for use in any Third World country, we have specified that it will be used in Mexico. This gives the design project an additional note of realism and direction.

There are a number of other important design considerations.

  1. Most peasant farmers in Mexico and Central America have hillside plots, the more desirable land being in the hands of large landowners. So a plow with a high center of gravity which would be easily overturned would not be appropriate.
  2. The plow should probably be designed to be operated by one or at the most two people; but farming is usually labor-intensive in third- world countries, and the need for additional people to operate the plow would probably not be an obstacle.
  3. The plow should be relatively simple to operate and maintain; replacement parts must be easily available.
  4. Finally, the cost should be under $1000.


In Mexico, as in many Third World countries, those who are engaged in agriculture can be roughly divided into two groups: large landowners and small subsistence farmers. For the most part, the large landowners have done a good job of keeping up with technological changes, and they have had the financial ability to incorporate those changes. For poor farmers, the situation has been very different.

While the Mexican government has taken some steps towards land redistribution, 65% of the farmers hold less than 5 hectares of land. This diminishes the advantage of technology, which usually depends upon scale. Further, the land owned by these farmers is in the hills and mountainous terrain. It's difficult to transport and manipulate large machinery in these areas. Finally, water projects for increasing irrigation have generally not benefited the rural population, which remains dependent on the rains.

If large farms can achieve efficiencies of scale, small farms will be unable to compete and may eventually be driven out of business. One might argue that it is better to let these small farmers get out of the agricultural business altogether. By allowing large farms to produce the agricultural needs for Mexico, the peasants can be moved to populated areas to work in industry.

Yet this solution seems patently wrong for three reasons.

  1. Agrarianism is an important part of the Mexican cultural heritage. Many peasants want to remain close to the land and to continue to be a part of rural life.
  2. The agrarian economy can support many more individuals than the industrial sector of Mexico. Prior to the 1970s, Mexico's economy was expanding due to the influx of petrodollars, and advances were being made in reorienting Mexico's population towards a Western model. However, with the rise of inflation in the Seventies, and a crushing foreign debt load, those advances have stopped. Thus, if a way could be found to increase agricultural yields without forcing rural flight, the economy as a whole would benefit.
  3. The agricultural sector has had difficulty in recent years meeting goals of self-sufficiency for production of staple crops, such as maize and beans. It would be highly desirable, then, to increase yields on all available farmland.

Since supporting small farms is important to Mexico's immediate future, making small farming more efficient is an immediate need. One way of doing this is by producing a small plow that is appropriate for subsistence farming. Such a plow might increase crop yields and also lessen the backbreaking work of hand farming.

The development of a small plow might be a mixed blessing, however.

A first consideration for anyone interested in mechanizing small farming is that the rural economy places considerable value on animal ownership. Draft animals can be used for plowing and transport, and the calves can be sold for meat. In fact, a draft animal is an important asset for the farmer, because it can be sold if he is in financial distress. How a mechanization project affects animal ownership is thus an important consideration.

A second consideration is that the small farmer is very risk averse. More technologically advanced farming might provide 120 bushels one year and 25 bushels the next, whereas less advanced farming might produce 60 bushels of maize in a good year and 50 in a bad year. Given the choice between these two options, the small farmer would probably choose the second. This is because the small farmer is interested first in providing for his family, and only then in selling for profit. Thus, if the costs of operation of a plow are too high, or detrimental to the soil or has other features tending to increase risk, farmers may not adopt it. Even if the plow is provided to them without charge, they may not accept it if it is perceived as substantially increasing risk.

Another consideration is that care should be taken lest technology is seen as foreign, or as an affront to the culture of the farmers. Artifacts seen as foreign sometimes convey the wrong cultural message: "their way is good and ours is bad." This tends to undermine cultural identity and social solidarity. Technological artifacts with which people can identify, and which can be seen as supportive rather than destructive of their culture, will be more likely to be accepted.

The history of the Loriana stove is often used by anthropologist as an example of the problems of introducing Western technology into non- Western societies. The stove is twice as efficient in its use of wood fuel as the indigenous Guatemalan peasant stove. But the Mayan Indians think of it as something non-Indian. The use of the stove is interpreted as an admission that the technology of others — i.e. of the Spanish and of North Americans — is superior to Indian ways.

There is another problem with the Loriana stove that emphasizes the importance of knowing the audience for whom one is designing. The stove gives off less heat than the traditional Indian method of cooking. Even though this is connected with its greater efficiency, it has a disadvantage. The main heating source of Indian housing is the stove. Use of the Loriana stove by Indians in the mountains regions of Guatemala means their homes are cold. If the designers had known this, they might have decided that making a more efficient stove should not be one of the design goals. They might even have decided that the Indians did not need a new stove.

Here is a final consideration. One means used to assist in making decisions about technology is cost/benefit analysis or highestutility analysis. This method requires the engineer to select the design option that will produce the greatest benefits relative to cost. This method has come under considerable criticism, however. One criticism is that the benefits could be maximized without being equitably distributed. The best way to maximize the total benefit from the plow might be to provide plows to the most ambitious and capable of the small farmers. They would probably use the plow most efficiently. The plow might also enable the more capable farmers to become even wealthier, relative to their less capable and ambitious neighbors. The overall utility might be highest, yet the distribution of wealth resulting from this approach could be even more uneven. One might argue that rewarding efficiency is a good thing for the society, but this is a value judgment. The important thing to keep in mind is that introducing Western technology can initiate important social changes.

We tend to assume that technological improvement is always a good thing. Unfortunately, introducing new technology may destroy or seriously modify a culture, and this may or may not be desirable.

Cost/benefit analysis is only useful if it can specify and quantify all relevant factors in a decision. Obviously we do not have perfect information for any case, but if cost/benefit analysis systematically undervalues certain aspects, such as cultural or moral factors (as Thompson argues), then the decision made on the basis of cost/benefit analysis will be flawed.

In the end, the choices made in designing the plow are going to have many ramifications. One writer has pointed out that:

The telling fact is that agricultural science and technology, like all technologies, have no inherent value; their human value is manifested only by the results achieved when they are properly applied to serve the need for which they were created.

Design Considerations

Here is a list of considerations that you should keep in mind when designing the plow:
  1. The plow could be designed to require two or more operators. Generally there is an abundance of human labor in subsistence farming.
  2. The plow should not cost more than $1000.
  3. The plow should be easily maintained. The tools available for repair will probably be minimal, and the level of mechanical expertise will probably be low. Also, the parts should be easily available.
  4. The plow should be easily operable. The operators will have minimal skills with machinery, and extensive training would be impossible.
  5. The plow should use fossil fuels that are readily available.
  6. The plow could either move under its own power or be pulled by a human being or a draft
  7. If possible, the plow should be safely operable on slopes of up to 30 degrees.
  8. The plow should be able to cultivate to a depth of 2-12 inches. The adjustments that vary the depth of plowing should be easy to make.
  9. The plow should be able to cultivate more than.2 hectare/day; which is the amount of cultivation that could be expected if draft animals were used. Since the operating costs of a plow are greater than the maintaining costs of an animal, the greater efficiency of the plow should offset this cost.
  10. Preventive maintenance should be easy. Parts will be difficult to come by, and factory service technicians may be nonexistent. Any maintenance which can prevent problems before they occur will add significantly to machinery life.
  11. Since the storage and transport of fuel is an expense, a plow having a large gas tank is desirable.
  12. Mexican gasoline's octane rating is quite low. The compression ratio of the engine will have to be low, with a lower specific horsepower rating than would be normal with higher octane fuel.
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