Wed. 10/30/02

In our past few sessions, my group has started working on really bringing everything together, synthesizing the information that we have found so far, and developing the plan that we will eventually give in our final presentation.  Simultaneously, we worked together to come up with a format for our group website, which parallels the progression of our work.  The web page's first section will be the background information that we found in our preliminary research, which includes facts on logging, mining, ranching, agriculture, and industry in the Amazon Basin area.  (My part in this was primarily research on agricultural practices and on exactly what sort of agriculture is practiced in the Amazon.)  Our second section is the one where we define and quantify (as much as possible) the development problems in the Amazon.  Finally, we will have the "solutions" section, which will contain all the best ideas that we can come up with to solve the problems that we have identified.

Marion (another member of my team) and I have been talking outside of class about the agricultural component of development in the Amazon.  Our data show that incorrectly managed agriculture is one of the major causes of deforestation, and we are looking for ways to remedy that.  Marion has been looking into agroforestry practices.  I have been looking into terra preta, which is described in last week's update.  My idea right now is that terra preta could be used to make development in the Amazon more sustainable and rational by 1) making it possible to farm a single plot for an extended period of time, instead of having to move from plot to plot and waste land  2) increasing the productivity of a single plot, so that farmers don't need to clear as much land to get the yields that they need, or so that, if they have easy access to big markets, they can produce more goods and increase their profits, and 3) keeping the overall condition of the soil much better even after farming, so that the forest can move back into abandoned plots much faster than it normally could.  It would also be interesting to find out whether terra preta could eventually be used to revive plots of land that already have been mostly depleted, which would drastically reduce the necessity to cut down the rainforest at all.

I have been looking for more information on terra preta on several websites.  The website of the International Workshop on Anthropogenic Terra Preta Soils lists, among other things, many professors and researchers who are involved in projects with terra preta, and I am working on contacting some of them right now, because, despite my best efforts, I have been hard-pressed to find any more solid facts on terra preta than the ones that I already have.

Also, when I was reviewing the facts that I have collected to put on our team website under the "background" section, I began to realize that there are still some facts that we are lacking... simple things like statistics on what percentage of agriculture is done by whom.  This is something that we included in our inital definition of an A (development: by whom and how?) and it should not be overlooked.  I plan to work on filling in some gaps in the next few days, by revisiting the goals that we initially set for ourselves and seeing whether we are going in the right direction to fufill all of them.  I have checked out a number of books from the library, and I have a lot of old bookmarks that I can also use for this.  I realize that maybe I should have done that by now, but.... bad week.  :o(
This week, I have somewhat shifted the focus of my research to a topic which I had noted earlier but had not examined in depth.  This topic is something called "terra preta ," or dark earth, which is the subject of a good deal of current scientific research.  I have found a number of relevant web site and articles, but the bulk of my information here comes from an article by Charles C. Mann called "The Real Dirt on Rainforest Fertility" which was published online in Science Magazine in 2002.

    What is terra preta?
Terra preta is the name given to a special kind of soil that is found in the Amazon, which is strikingly different from all other soils in the area.  Most soils in the Amazon are oxisoils, which are very ill-suited for agriculture.  They are highly acidic, and they are low in organic matter and nutrients, because the carbon and nutrients are primarily stored in the vegetation covering the oxisoils.  Therefore, when land is cleared for agriculture, oxisoils are left with few nutrients, so they become completely depleted after they are used for agriculture for only 2 or 3 years.

Terra preta, on the other hand, yields great productivity and long-lasting fertility.  Furthermore, it seems to actually be the product of previous intensive agricultural activity in the Amazon.  This indicates that some kind of sustainable, intensive agriculture is possible in the Amazon.  Bruno Glaser, a chemist at the Institute of Soil Science and Soil Geography at the University of Bayreuth, Germany, says that "[Precontact Amerindian populations] practiced agriculture here for centuries.  But instead of destroying the soil, they improved it--and that is something we don't know how to do today"  (C.C. Mann, Science Magazine).

Terra preta has more "plant-available" nutrients (P, Ca, S, N) and more organic matter than oxisoils.  It also retains moisture and nutrients better.

There are three major factors that make terra preta different from regular oxisoils.
  1. CHARCOAL-- Terra preta contains up to 70 times as much charcoal as oxisoils.  Charcoal prevents organic matter from being rapidly mineralized.  It also partly oxidizes over time, which keeps providing sites for nutrients to bind to.  Experimentally, when plots of rice and sorghum were treated with different combinations of fertilizers and charcoal over a period of three years, the charcoal "was really making a difference" by the second year, and in the end, plots treated with a combination of charcoal and fertilizers yielded as much as 880% more than plots with only fertilizer.
  2. NUTRIENTS -- Charcoal alone is not enough.   In the experiment mentioned above, plots with charcoal but without fertilizer did not produce very much.  High nutrient inputs are also key.
  3. MICROFAUNA -- Janice Thies, a soil ecologist from Cornell, says that "there are indications that microbial biomass is higher in terra preta" (C.C. Mann, Science Magazine).  These special soil microorganisms probably also play a role in terra preta's persistent fertility.

    How is it created?
In the past, terra preta was probably created through a method that scientists are calling "slash-and-char," as opposed to slash and burn.  In this method, farmers only burned organic matter incompletely, and then stirred it directly into the soil.  They also added nutrients via excrement and waste such as animal bones.  In the Amazon today, the creation of "ingredients" for terra preta might be an excellent use for unwanted waste and excrement from cattle and from cities.

These days, scientist are hard at work trying to create new terra preta.  It is possible that they could create a "package" of charcoal, nutrients, and microfauna that could be added to regular oxisoils the transform them into terra preta.  If this could be done economically and distributed efficiently, it would have a very positive effect on sustainable agricultural development.  If farmers could use less land to get the same end product as before, and could remain on a single land plot indefinitely, then the rate of deforestation due to agriculture could be slowed dramatically.

    What's the catch?
Although it's easy to get excited about terra preta, there are some complications with using it.  First, it would be essential to develop new techniques to control tropical weeds.  Soil that is conducive to the growth of crops is also conducive to the growth of weeds, so crops on terra preta fields can be completely overwhelmed by weeds.  If this happens, farmers have to abandon their fields and clear new sites for agriculture, which is exactly the problem that we are trying to eliminate.

Second, terra preta has to be managed competently.  When it is poorly managed, its nutrients can decline back to near-oxisoil levels.

Third, concerns have been expressed that terra preta might not be economically viable in remote parts of Amazonia, because the benefit of increased yields depend on quickly transporting produce and fruit to large markets.  I would argue that this is not necessarily an issue, though; farmers do not necessarily have to produce more just because they have more productive land.  The other option is to simply farm on less land.

Finally, is is possible that success with terra preta will simply encourage more people to farm the Amazon, and forest will be cleared due to that.  This seems to me like a valid concern, and it is something that we will have to keep in mind.

Despite possible complications, I think that terra preta holds some exciting possibilities.  I plan to continue researching it for a while longer, both by browsing the web for more detailed articles and by contacting, via email, some of the scientists who have been involved in terra preta projects and research.

Over the past couple of weeks, our group has been working to organize itself and focus in on our key ideas.  My recent research has focused primarily on Brazilian agriculture.  I have been trying to find details on agricultural practices, but these are hard to come by.  I have, however, found information about Brazil's agricultural production and its past and present land use, and information about agricultural practices in general.

These are some statistics on land use in Brazil, from the Instituto Brazileiro de Geografia e Estatistica (IBGE) .  These numbers do not distinguish between land that is and is not part of the Amazon, but they do give a decent sketch of the way land is used in Brazil in general and they show how land use patterns have changed over time.

total (in millions of hectares)
permanent crops
temporary crops
fallow land
natural pastures
planted pastures
natural woods
planted woods
"productive land" not in use

The IBGE defines each of these terms as follows:
It is important to note here that IBGE does not define "temporary" crops in the same sense as we have been.  Our group tends to think of temporary crops as the ones that will be abandoned, leaving the land fallow, after several years, but here they are simply defined as crops that require re-seeding.  This does connect to our group's idea of temporary crops, but it is not exactly the same.  Some interesting trends in the data are: productive land not in use is steadily decreasing, natural pastures are being replace by planted pastures, there was a decrease in fallow land between 1985 and 1995, and the area of temporary crops has been steadily and rapidly increasing.

The IBGE also has a breakdown of land use by state, telling each state's total land use, permanent and temporary crops, natural and artificial pastures, natural and planted woods, and fallow lands and productive lands not in use.  This can give us a more geographically precise idea of how land is used, and can be viewed here:

I also found (again on IBGE) a list of the quantities of different farm products that were harvested in 2001, the quantity that will be gathered in 2002, and the percent change between these years.  I will not reproduce the entire chart, but will give the numbers for the ten most produced farm products.

Farm Products
Area (in ha, rounded to nearest 1,000)

harvest gathered in 2001
harvest to be gathered in 2002
% change
1) Soybeans (grain)
2) Corn (grain) 1st harvest
3) Sugar cane
4) Rice (in husk)
5) Corn (grain) 2nd harvest
6/7) Coffee beans
7/6) Beans (grain) 1st harvest
8) Wheat
9) Cassava
10) Beans (grain) 2nd harvest

We can see from this that soybeans and corn alone make up more than 50% of the harvest of farm products by area.  Also, since we are trying to minimize deforestation, it makes sense for us to focus on the crops that take up the most area.  Therefore, I have tried to find some information about best practices for soybeans and corn.  So far I have not found any information that is specific to the Amazon, but I have found that the Ohio Agronomy Guide (link coming very soon) has good information about soybean production in general, including issues such as fertilization, disease control, planting dates, weed control, and variety selection.

This week I did some independent research on agricultural practices in the Amazon.  I focused on this topic because I found in my general research that one large contributer to deforestation is ill-managed agriculture, so one way to reduce deforestation greatly could be to find ways to make agriculture more efficient and environmentally friendly.  That way, necessary agricultural development could continue with minimal damage to the ecosystem.

From Sustainable Settlement in the Brazilian Amazon1 (1995):
High productivity farming tends to have two effects:
1) Retention of land is high, so deforestation is contained to a certain area.  
2) There is high deforestation on the plots that are occupied; the forest will probably never grow back there.
The enviromental costs that arise from this sort of farming are loss of biodiversity and erosion of soil.  These things are difficult to measure, but it is possible to identify the conditions under which they are reduced.  (For instance, when there is greater yield per acre of land, enviornmental costs will be lower.)

Three measures that would promote sustainability are:
1)  Reduce environmental cost per private benefit.
2)  Increase private costs of deforestation.
3)  Decrease private cost of environmental alternatives such as alternative tropical farming technology.

From Amazonia: Agriculture and Land Use Research2(1982)
Little has been done to understand the Amazon's potential adaptability for annual food crops.  Some information suggest that, with adequate scientific knowledge, it would be possible to gradually develop the Amazon's agricultural potential, through the careful manipulation of existing conditions and through the generation of an equilibrium between different types of crops (annual, perrenial, forest).

Different agricultural methods:
"Shifting agriculture," commonly known as slash and burn, is the most widely used method in the humid tropics.  As you would expect, it consists of cutting down the vegetation in an area, burning it, farming the plot for 2 or 3 years until the soil is depleted, and then moving on to a new plot.  Unfortunately, when the population of an area increases enough, this practice becomes disruptive of the ecological balance.  Additionally, its average yields are relatively low.  

Mechanized clearing (i.e. bulldozing) is even worse than slash and burn in many ways.  In the slash and burn method, ashes return to the ground and replenish the soil's (very important) nutrients.  This doesn't happen with the mechanized clearing.  Mechanized clearing also causes problems of soil compacting (causing water infiltration rates to decrease from 10.5 cm/hr to only 0.5 cm/hr in one study), and disrupts the fragile surface layer of soil.

 A number of systems for continous cropping of annual plants exist, which are all improvements over these two methods.
Intercropping--the cultivation of multiple crop species simultaneously in the same area.
Experimentally, implementations of this give figures such as 50% and 60% better yield per unit of land.  This system minimizes competition for light, water, and nutrients, allows for more efficient management of diseases, insects, weeds, and soil, permits better diversity of crops, and just uses land more efficiently.  This works best on small farms, although the author states that intercropping of annuals and perennials "offers promising perspectives."

Relay system
--the planting of a second crop before the flowering or harvesting of a first
This gives better yields than intercropping because it reduces the periods of competition between crops, but it also seems to create environments that encourage the spread of pathogens.

Sequential rotational system for annual crops
This is often used commercially, and is viable for an extended period of time (7+ years in one study).  Of these three systems, it seems to be the most efficient and effective in large scale operations.

Regardless of the system, certain things are always important, such as:

Conclusions that can be drawn are:

When population density is high enough, agriculture with annual crops should be permanent and continuous instead of shifting.  The step from shifting to continuous agriculture requires:

Continuous cultivation in the Amazonia is feasible if these things are all taken into account.

There is still much research that needs to be done.  Some relevant fields of research are better farming technology and genetic studies/selection of other crops that could be grown sucessfuly in the Amazon area.

1.  Sustainable Settlement in the Brazilian Amazon. Anna Luiza Ozorio de Almeida and Joao S. Campari, Oxford Universtiy Press, New York, 1995.
2. Amazonia: Agriculture and Land Use Research. ed. Susanna Hecht, Cali. Columbia, Centro Internacional de Agricultura Tropical, 1982.

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