Understanding Tropical Soils: Part 5

This article is continued from Understanding Tropical Soils: Part 4.

by Dexter B. Dombro

 

Making soil with biochar and compost.

Now that we have discussed some of the common problems with tropical soils, it makes sense to ask what might be the objective of using non-chemical fertilizers in tropical forestry. The simplest answer is sustainability. By this we mean more than just maintaining something at a certain rate or level. When we are talking about environmental and agricultural sustainability, we are talking about a jig-saw puzzle of interconnected pieces that produce a lasting and positive outcome. While paying the bills and being profitable are a necessary part of sustainability, the other side of that equation are better practices, better biodiversity, healthier plants and trees that imply healthier humans and the satisfaction of knowing that one is Earth-friendly. Sustainability is all of those things and more.

Agrochemicals aren't sustainable.

The soil has a soul. It is more than just a medium in which we plant things. It is full of life, the very foundation of biodiversity. Bad practices in forestry and agriculture that ignore the needs of the soil result in long term problems and a loss of sustainability. The use of chemical fertilizers, herbicides and pesticides result in dead soil, removing all of the natural components that help trees and plants to be healthy, replacing them with chemical substitutes that simply don’t do the job in the long term. Ironically, the so-called green revolution that produced bumper crops in dead soils is now facing a global backlash, as farmers go bankrupt, cancer rates spike, soils are no longer able to produce and biodiversity declines. Quick profits are not a replacement for sustainability, as people all over the world are discovering.

Cebu cows can save the Earth with the quality of their manure.

What are some of the negatives caused by using agrochemicals?

• The high cost of chemical fertilizers, herbicides and pesticides. This has led to an epidemic of suicides and bankruptcies by rural farmers in many developing countries. 
• The high cost of transportation to haul chemical fertilizers, herbicides and pesticides to rural areas from urban factories. 
• In order to maintain productivity, ever increasing amounts of chemical fertilizers are needed, until it is simply no longer profitable for the farmer or the forester. 
• Dead soil and a loss of the soil’s microfauna, including earth worms, soil fungi and more, with the resultant loss of biodiversity as other creatures in the food chain are affected, all the way up to humans. 
• The loss of honey bees due to the use of herbicides and pesticides, leading to a pollination crisis in many places. 
• Agrochemicals, especially when used in tropical soils with poor nutrient retention, can experience losses as bad as 90%, which is a very bad investment, with those chemicals ending up in the ground water and rivers. 
• Agrochemicals do not make the nutrients trees and plants need bio-available in the same way that earth worms, fungi and other microfauna make those nutrients bio-available. 
• It doesn’t take a genius to realize that agrochemicals cause environmental contamination. 
• Crops, be they forestry or food related, are less resistant to plagues and diseases, requiring the application of other chemicals before they can be harvested or appear on your plate. 
• Serious health effects on humans. For example, Argentina is now suffering from an explosion of agrochemical related illnesses. 
• The constant use of agrochemicals causes the soil to be more compacted, asphyxiating the soil. 
• The constant use of agrochemicals results in the soil losing its cationic exchange capacity (CEC – see Part 1), in other words it further aggravates problems with soil nutrient retention. 
•  Agrochemicals cannot be consumed by earth worms and other beneficial creatures living in the soil. 
• The quality of products being produced is poorer, especially where foods are concerned (flavor, ingredients etc.)

Tree planting bags with organic soil at La Pedregoza.

What are some of the benefits of implementing natural silviculture and organic agriculture solutions?

• The use of local resources to make fertilizers at a significantly reduced cost. 
•  No costly transport of fertilizers over large distances. 
• Higher labor requirements resulting in greater local socioeconomic benefits, but still cheaper than the purchase of agrochemicals and their transport. 
• Soil that is alive and healthy. 
• The avoidance of environmental problems and degradation. 
• Less plagues and diseases affecting one’s trees or crops. 
• Production results that are equal to those achieved with agrochemicals, and superior when done with soil amendments like biochar (see Part 2). 
• Organically managed soils have significantly better cationic exchange capacity (see Part 1) and soil nutrient retention. 
• The forester or farmer is producing significantly less residual solids and contaminating garbage. 
• Virtually all nutrients produced in natural silviculture and organic farming are bio-available to the trees and plants. 
• Healthy organic soils have better water retention in the dry season. 
• Organic fertilizers do not burn the roots of the trees or plants, a common problem with chemical fertilizers. 
• A lot less soil acidity, especially in tropical soils, with the use of organic materials. 
• Soils that are organically managed are less compacted and better aerated, which in turn assists soil microfauna. 
• Forestry and agriculture that is more profitable. 
•  Plantations and farms which are more sustainable and Earth-friendly, with healthier humans living and working in them.

Tree planting in healthy, organic soil.

I hope this series of 5 articles will help to explain some of the problems faced by tree planters in tropical soils, and also lead to a greater awareness of the importance of managing the soil in an environmentally friendly manner. At the Amazonia Reforestation and CO2 Tropical Trees plantations in Vichada, the La Pedregoza team is developing a new way of doing things that we like to call “natural silviculture”. This goes beyond being merely organic, to include biodiversity considerations, such as using local earth worms instead of imported California red worms. It includes amending the soil to become less acidic, with better nutrient retention, for improved crops and forest cultivations. It means applying analog forestry considerations and recreating ancient technologies like Terra Preta and Jivamritham. Perhaps most importantly it means becoming a model of sustainable forestry that others can copy, no matter where they are located, by using local resources and ingenuity.

Understanding Tropical Soils: Part 2

Continued from Understanding Tropical Soils: Part 1

by Dexter B. Dombro

 

Sandy tropical soil has almost no CEC.

Now that we know the two most serious handicaps faced by tropical foresters, the low cation exchange capacity (CEC) and the acidic pH of the soil, the question is what can we do about it? The answer, surprisingly, can be found in the past. Spanish and Portuguese conquistadors noted that some indigenous communities in the Amazon had highly productive, multi-year food cultivations. This phenomenon continued into the present, at which point some scientists started to wonder why certain Amazon River basin communities had dark, productive soils. The term Terra Preta or black soil was coined from Brazilian Portuguese to describe this phenomenon. Archaeologists and others conducted excavations near indigenous Amazon communities, and discovered that the native people in pre-conquest South America had mixed charcoal and clay pottery shards into the soil they were cultivating. Since then, similar observations have been made in Africa and Asia at ancient sites.

Black soil in the tropics with biochar.

Very quickly scientists realized that those ancestors had known something we have forgotten. Charcoal in the soil can act as a retention agent, stopping nutrients, micro-fauna and fertilizers from being leached from tropical soils during heavy rainfalls. It allows organic material in the soil to build up, thereby providing plants and trees with a much better and more productive natural environment in which to grow. Clay has a similar retaining capacity, which would explain the use of the broken pottery shards. Obviously, the charcoal from fires and broken pottery were added to the soil as a means of creating Terra Preta in ancient times, thereby boosting food production and the quality of cultivations in pre-conquest indigenous communities. This led scientists and modern agriculturists to ask the obvious question: how can modern planters benefit from this knowledge? The list of benefits, as it turns out, is amazing and can be applied anywhere in the world, not just in the tropics.

Charcoal in the soil can act as a retention agent, stopping nutrients, micro-fauna and fertilizers from being leached from tropical soils during heavy rainfalls. It allows organic material in the soil to build up, thereby providing plants and trees with a much better and more productive natural environment in which to grow. 

Charcoal can be made of any organic matter.

    Charcoal when embedded in the soil has a half-life of 1,000 years. Why is this important, you ask? Simply put, this means that charcoal obtained from organic matter and woody biomass can be sequestered in the soil for centuries, making it an extremely effective and potent way of capturing and storing atmospheric carbon on a very long term basis. Done on a worldwide basis this could be an important tool in the struggle against climate change.

Note dark soil near surface - nutrients.

The charcoal can’t be placed in the soil on its own. It first needs to be charged with an organic fertilizer, like compost, cow manure or cow urine (urea). Charcoal is negative and on its own would attract all the nutrients in the soil, taking them away from the plants and trees. However, once charged, it becomes a potent agent for retaining and holding nutrients, organic material and therefore micro-fauna in the soil. A new term has been adopted to describe charged charcoal for agricultural use: biochar.

Worldwide interest in biochar is huge.

The process of making biochar also results in the production of wood ashes. Those ashes, when added to the soil at the same time turn out to be full of essential elements required by trees, such as boron (Chemical: B), phosphorus (P) and potassium (K). But perhaps more importantly, wood ashes are almost 10 times more alkaline than lime, meaning that in controlled applications they can reduce or neutralize soil acidity, thereby greatly enhancing agricultural productivity and the range of species that can be cultivated. 

On the economic side of the equation, biochar can be produced using local resources. In India rice husks are charred, charged with cow urine and then added to the soil. Virtually any organic material can be charred and processed. This means that poor farmers, tree planters and communities in developing countries can not only enhance and improve their own soils, but also fertilize them with local resources, thereby eliminating high and environmentally unfriendly transportation costs for expensive chemical fertilizers and limes that kill the microfauna, leaving dead soil behind.

                                      Biochar and wood ash  can be added to tropical soil before planting.

Clay in soil can prevent drainage too.

Needless to say, this is all very exciting, but still faces some technical challenges. For example, how can biochar be produced on a large scale? How can it be added to existing tree cultivations? Where does the required biomass come from? The answer to these and other questions can be found in the approach being taken by Amazonia Reforestation and CO2Tropical Trees at their La Pedregoza and El Encierro plantations in Vichada, Colombia. Let’s examine some of the solutions being developed in Part 3 of this series of articles.

Understanding Tropical Soils: Part 1

by Dexter B. Dombro

Tropical tree plantation in sandy acidic soil.

Tropical forests are the lungs of our planet. 95% of all tree-based carbon sequestration occurs in the tropics, primarily between both 15° northern and 15° southern latitudes from the equator. The huge forests of Canada, Russia and Scandinavia and other temperate zones only account for 5% of tree-based carbon capture. This means that the decline of tropical forests is a huge cause of climate change. Many studies show that tropical deforestation emits greenhouse gases (GHG) and may well be the leading cause of desertification of the Earth. All trees play important roles in removing CO2 from the atmosphere, but also other dangerous contaminants. They help hold ground water and thanks to the process of transpiration are crucial for cloud seeding and the maintenance of global rainfall patterns. Needless to say, forests also account for 90% of terrestrial biodiversity, making them essential habitats for life on our planet.

Imagine transpiration being like tree sweat.

However, planting trees, especially tropical trees, involves more than just sticking a seedling in the ground. Tropical soils are often poor and acidic, in large part due to millennia of torrential rains that have leached the nutrients and organic material out of the soul, a process called lixiviation. For example, the grasslands of eastern Colombia (llanos orientales) and Venezuela have soils that are mainly composed of sand, ferrous oxide gravels and some clay. Similar conditions exist in large parts of Brazil and in the Amazon basin. This is why Amazon deforestation is such a huge problem: poor people cut down trees to grow subsistence crops, collect one harvest and then find that the soil is depleted, so they repeat the process, cutting down more rainforest. Unfortunately, this is the definition of insanity, doing the same thing over and over again, expecting different results each time.

Tropical deforestation

I don’t want to bore you, but it is important to understand two key issues involving tropical soils. The first issue is acidity, measured in a logarithmic scale from 1 to 14, with a pH below 7 being acidic, while a pH over 7 is alkaline. Logarithmic means that each number on the scale is either 10 times more acidic or 10 times more alkaline than the previous number. A pH of 7 is considered neutral and is the value of pure water. Most plants do very well in neutral soils. However, the majority of tropical soils are acidic, which means that native trees and plants have had to adapt to acidic soil conditions. For example, the soil at La Pedregoza in the Orinoco River basin of Colombia has an average pH of 5.9, meaning it is 90 times more acidic than pure water. The traditional agricultural solution to soil acidity is to dump tons of lime on the soil, in order to achieve a more neutral pH, without regard to the cost or the damage done to micro-fauna.

Cation Exchange Capacity or CEC

The second issue is something called the cation exchange capacity or CEC of the soil. For simplicity’s sake this is best described as the capacity of the soil to retain nutrients, be that organic material, micro-fauna or fertilizers. CEC is measured on a scale of 0 to 50, with 0 being soil that has complete filtration or lixiviation of any nutrients, making for rapid drainage with no retention of any kind. In contrast, soil with a CEC of 50 is solid rock or hard clay, which does not allow for drainage, causing plants and their roots to drown. In the case of tropical soils the majority have a very low CEC. For example, the average effective CEC of soils at La Pedregoza is around 1, so pretty much total filtration of the soil with very little retention of nutrients, organic material or micro-fauna. This explains why rainforest trees are complete recyclers, drawing the majority of their requirements from the atmosphere and from the dead fall of leaves, branches and other organic matter inside the forest. They have very little dependence on the soil for their food requirements. Now you know why rainforest deforestation in the tropics produces such poor agricultural results.

Typical soil sample analysis from the Orinoco River basin. CIC is CEC in Spanish, while CICE means the  effective retention of the soil. Note the pH of the soil meaning it's very acidic in its natural state. Also note how poor the soil is in elements.

In Part 2 of this series of articles, I will address the most promising solution to the nutrient retention and acidity problem in tropical soils. That solution has positive implications for carbon sequestration, plant nutrition, enhanced agricultural and agroforestry production, is financially sustainable and has huge socio-economic development benefits in tropical regions. It is also 100% organic and natural, without any chemical or artificial elements.