My Independent Study for Summer, 2011

My independent study project for my University was to create a dry land fruit orchard in the semi arid mountains of central Mexico. The project involved the strategic planting of selected fruit tree varieties on the face of a hill, with the implementation of water harvesting earthworks.  I worked on this project with one other co-designer and other helpers to assist in the manual labor. Our site was in central Mexico, at about 6,000 ft above sea level.  The climate we were working in is as much temperate as it is arid. There is a very, very wet raining season in the summer, and an extremely dry season throughout the rest of the year.  The sun is extremely strong and days are hot; but nights can get cold and in winter frosts are common. The objectives of the project were to create an edible orchard and lay down the foundations for a future food forest, as well as regenerate the water table on the site to enable self-irrigation in the years to come.

Our site during the dry season

We approached the project with a lot of confidence.  I had spent 6 weeks in Arizona learning how to create water-harvesting earthworks for trees.  My co-designer Alex had spent the past 4 summers working for a garden and landscaping business in the greater Boston area, so he had planted thousands of trees and knew quite a bit about tree care.  As with most projects of this nature, it turned out there were quite a bit of unforeseen changes in plan and challenges that developed along the way; mostly originating from the manner in which we began the project.

We decided to undertake this project about a week before the owner of the land told us a backhoe was going to the land the next day to dig holes for the tress.  We then realized that we had to go out in the morning and figure our where the holes should be dug, on the spot, without any prior placement planning or slope and contour measurements.  This was a very undesirable to begin this project, but our boss said it was the only day the backhoe was available.  We later discovered that assuming we even needed a backhoe was also somewhat of a mistake.  I will elaborate on this later.

We placed the holes in a diamond pattern on the hill, using strides to measure the distance between them.  This way we had plenty of room between the trees, about 4 meters, and we also had room to create basins and swales in front.

After our holes were made we had to decide what types of trees we were going to plant based on the resources available.

The following highlights the steps we took after the initial holes were created:

The Backhoe

displays the hole placement

Part 1: Surveying and Design

Gaining a thorough understanding of the land and available resources was the first step in deciding what trees to plant.  The soil, annual rainfall, climatic temperatures and native plant life all had to be taken into consideration before we could make selections.  Our site was approximately 800 sq. yards located on the bottom half of a southwest facing slope.

The soil of San Miguel de Allende has a very alkaline ph level, many rocks and a high percentage of clay.  The high alkalinity is caused by the high amount of minerals and salts leftover from water that evaporates during the dry season.  The soil and climate of this area in Mexico are very similar to parts of the Mediterranean; sunny, warm days, cool nights, dry air and alkaline soil.  Therefore we were able make tree selections based on what we know grows well in a “Mediterranean climate”, such as citrus, avocados and olives.  The soil we surveyed contained a high amount of black and red clay.  Ideally soil will contain a balance of both large and small particles, with a higher amount of larger particles to promote water drainage.  Unfortunately our soil’s high clay content would make water drainage a slight issue.  Adequate drainage is vital for fruit trees, as many of these plants will rot or completely die if water is not able to flow freely away from their roots.

Rainfall was the biggest concern and consideration we had in planning for this project as well as the resource that was the primary influence of our design.  Our goal was to develop water-harvesting earthworks and use the slope of the hill to direct and control the flow of rainwater in order to allow for passive irrigation of the trees. The winter, spring, and part of the summer in San Miguel are dry with little to no rainfall.  Generally beginning in May there is rainy season that extends into September.  During this time period there is rainfall almost every day that transforms the land and plant life from a dry desert into lush grasslands and forests.  Our overall goal was to harvest the maximum amount of water during the rainy season in order to recharge the water table, which would then supply water to the trees through the dry months.

San Miguel has a very high elevation of about 6,000ft above sea level.  During the winter temperatures can reach as low sixteen degrees Fahrenheit, and during the late spring and early summer, as high as one hundred degrees Fahrenheit.  Accordingly, the months without rainfall are extremely dry and the months with rainfall are dry to moderately humid.  This is important for two reasons:  the dry climate makes for very fast evaporation, making water all that more difficult to store and be absorbed into the soil.  Also, the extremely low temperatures that can be reached are a limiting factor for tree we can plant.  Although the average temperature in San Miguel is quite warm, many of the heat loving plants that one can find farther south, such as avocados and mangos, would not survive through the winter.

The final aspect of the land that we studied was the already existing plant life.  Like much of Mexico, San Miguel is home to many varieties of cactus.  Another family of spiky plants that are abundant in the area is Acacias.  These plants can be as small as one-foot tall shrubs or as large as fifteen-foot tall trees.  Mesquite is a tree that is part of the Acacia family and grows abundantly in the area.  However our particular site was a slightly higher elevation than most and Mesquites could not survive the winter frosts.  Instead our land was full of Wuisache, or sweet Acacia trees.  Both Mesquite and Wuisache are leguminous and produce pea pods that eventually fall to the ground.  For a while we thought that the Wuisache trees were Mesquite.  Although they look very similar and both produce pods, the pods of the Wuisache are not edible like the Mesquite.  However they are still beneficial because they provide the soil with a constant supply of Nitrogen, which is a crucial element in the development and growth of food crops.  These native legumes would act as our nitrogen fixers and also provide shade and wind break for our young trees.

Part 2: Tree Selection

Taking into account all of the above information, we were able to narrow down the type of trees that we could plant.  We needed trees that were cold hardy, could thrive in alkaline soil, did well with strong sun and a dry climate, and could withstand droughts.  Initially this seemed like a tall order to fill, but from investigations into what other people were growing as well in the area as well as similar climates found in other countries, we were able to generate a diverse list of fruit trees.

A feature of the San Miguel area that holds true in many parts of Mexico, that I really found inspiring was the enthusiasm and support of organic, small scale farming.  Unlike the large scale industrial agriculture found in the USA, much of Mexico’s food is still produced by small farmers and then sold directly in the nearby communities and cities. Because of this we were able to find many small scale farmers in the area to give us advice about trees.  In fact there was a farmer that lived directly next to our site and he turned out the be the most helpful because he brought to our attention that the slightly higher altitude of that site made a big difference for which trees could make it through the winter.  He advised us not to plant any avocados, guayabana and only a small selection of citrus.  Initially we wanted to plant several nut varieties, but we were told that most nut trees did not fare well and that the safest bet would be Pecans.  Our research told us to stay away from plums because they like acidic soil.  However we spoke to a local farmer that said they grew well on his land and recommended we plant them.

The fruit trees we ended up planting are as follows: Pomegranate, Peach, Plum, Olive, Mandarin, Pecan, Apple, Apricot, Pear and Limon (a native Mexican variety of Lime).  In total we planted 40 trees.  These trees had characteristics that were best suited to the climate of our site.  For example, Olives, which come from the Mediterranean, are an excellent choice for our site.  They love a dry and hot climate and can withstand the colder temperatures of the winter.  Similarly, Pomegranate is well suited for a dry climate and Mandarin’s, being the hardiest citrus variety, would do well in the hot climate, but also make it through the harsh winter.  Other plants such as Apples, Apricots, and Peaches were also shown to be tolerant of the local conditions.  The rest of the plants, the Plums, Pears, Limon and Pecan, were originally not our first choices but because of the advise of local farmers we decided to plant them.

Part 3: Planting and Land Amendment

An important part of this process was finding methods that would necessitate the least amount of energy input with the greatest amount of benefit.  When deciding how to dig the holes for the trees, for example, we initially thought it was much more efficient to use a back hoe to dig the holes instead of digging them by hand.  Although this meant using heavy equipment and burning fossil fuels, it would ultimately save a good deal of time, money, and human labor. All of the holes were dug roughly two to three feet deep and four feet in diameter, with some being even larger.  It turned out we ended up spending a great deal of time filling the holes back in with dirt because they were dug too big.

It is still debatable whether the backhoe was a good or bad idea.  On the one hand it broke up the very dry earth and made it much easier to create earthworks and prepared the soil for the tree roots.  On the other hand we spent hours refilling the holes and then later discovered a study that said the popular belief that you must create a meter-by-meter hole when planting a fruit tree is actually myth.  I think ultimately the backhoe was helpful but it dug the holes way too big.

After talking to people in the area and doing our own research we decided we needed to plant the trees on raised mounds and form a basin in the front for water catchment.  In Bill Mollisons Permaculture book he shows a picture of a sloping hill with a swale and berm formed on a contour line.  The trees are then planted in the raised earth below the swale.  Since the drainage of our soil was poor due to high clay content this was not an option.  Also it would not have been possible to work with the contour line because it was so inconsistent across the slope due to large rock clusters and boulders.  Instead we created individual swales in front of each tree.

This way the swales would still harvest water, but the force of gravity would prevent over saturation of the roots. In addition we created spillways that directed over flow into the swales below.  We also made sure to plant the most drought tolerant trees, such as Olive and Pecan on the top of the hill because they would get the least amount of water.  The more water loving citrus, apple and pear trees were planted at the bottom of the hill.

Before planting the trees we soaked their root balls in a micro rhizome bath. After planting the trees we top-dressed the mound with two buckets of compost mixed with a ¼ cup phosphoric rock.

the micro rhizome bath

mixing the phosphoric rock and compost

We were a bit nervous about the clay content being to high, but after doing research and talking to local farmers we learned that the trees would be just fine.  We only put compost on top of the tree because if compost is put in the hole the tree roots will linger in the nutrient rich area and not expand outwards.  The compost on top would slowly leach available phosphorus into the soil over time and not prevent root expansion.  A friend also told us it would be best to allow the trees to adapt to the existing soil and not make any amendments.

Creating the mounds, swales, and berms took up the majority of our laboring hours.   After we completed the planting process, we then used the abundant supply of rocks on the land to create a natural form of mulch, adding a layer of small rocks on top of the mounds to hinder weeds and keep moisture and hat from escaping during the dry winter.

basin and rock mulch

In addition to the swales and berms, we created spillways to direct the over flow from one basin to another. We also lined these with stones to deter erosion.

spillway

spillway lined with rocks

Part 4: Results

We started the planting process at the beginning of the rainy season.  When we began planting the land was yellow and dry, and lacked vegetation.  By the end of our project, the land had transformed into a rich, lush, green oasis with a wide variety of plants, shrubs, and trees.

our site before the rains

After a month of rain

Similarly, the trees followed this transformation.  As more water fell, the soil began to moisten and become enriched, making it more suitable for the trees to grow.  All of the trees quickly took and began to flourish, except for the pomegranates.  Much to our disappointment and surprise, only two out of the seven Pomegranates we planted survived.

apple blossom

apricot tree

Mandarin Tree

browning pomegranate

A number of factors could have contributed to their deaths. The man who sold them to us gave us one for free and had somewhat questionable merchandise.  Most of our trees came from an organic fruit orchard but the pomegranates, pecans and olives were purchased on the side of the highway.  They were not hearty or of good quality and were most likely grown with synthetic fertilizers.

Fortunately, many of the plants took to the land better than we had planned.  The Apricots and Pears, for example, flourished the best, with little to no leaf loss or yellowing, which is customary to newly transplanted trees.  As expected, the olives took well without a hitch and quickly established themselves.  The citrus plants, the Mandarin and Limon also took well, but our main concern was their ability to survive in the colder months.  If it gets too cold and there are consecutive frosts, the plants can be burnt and damaged, which could lead to growth difficulties or death.

Many of the plants lost a few leaves, but that was expected.  Taking everything into account, at the end of our time with the land we were very pleased with our work.  Almost all of the trees we planted took to the land well.  The water catchment systems we put in place immediately started to gather water.  The rock mulch looked beautiful, deterred weeds, and added to the moisture content of the soil.

Conclusion:

The amount of learning and hands on experience I gained from this project is immeasurable.  Having the opportunity to completely control and make decisions for a project of this size is very rare and therefore I feel even more grateful that I was able to take part in this.  The ability to work in another country and experience the people, culture, and different ways of thinking completely gave me a different perspective on the way I view my studies and what I want to do with my life in general.

What I gained most from this is the importance of thorough research and planning.  If we had not taken the time to contact several sources about what we were doing, we would have never had the success we experienced.  And even still more research and planning could have been done.  Creating this orchard with the intention of providing food for years to come was a wonderful experience. I think the most important thing I learned from this whole experience is that learning never stops and I will continue to be surprised, challenges and inspired for the rest of my life.

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