Sunday, January 26, 2014

Understanding Tropical Soils: Part 4

This article is continued from Understanding Tropical Soils: Part 3.
by Dexter B. Dombro

Biochar added to soil retains nutrients.
If you have ever seen the rapid drainage of tropical soils, you will understand why changing the CEC so that soil retention improves and nutrients don’t just filter or wash away is such an exciting prospect. However, having a pile of biomass converted to charcoal means we are not quite there yet. There is still the process of charging the charcoal so that it becomes biochar and can be added to the soil. What do we mean by charging? Simply put, charcoal is negative, and if we added it to the soil directly it would suck any nutrients in the soil away from the plants or trees it is supposed to benefit. This means we first have to convert the charcoal into something that is neutral or even positive, so that it retains the nutrients in the soil and makes them available to the plants or trees, without the nutrients being washed or filtered away.

Liquid fertilizer made with cow urine.
There are a lot of different ways in which biochar can be charged. At Amazonia Reforestation and CO2 Tropical Trees we use an ancient recipe known as Jivamritham, which is basically a soup or liquid fertilizer rich in microfauna. It is made out of 10 kg of cow manure, 10 liters of cow urine, 2 kg of legume flour (beans or lentils), 2 kg of molasses or panela or jaggary (first run-off of sugarcane), a handful of local soil, which is how local soil microfauna is added, and finally topped off with 200 liters of water. 250 liter tanks are used to make Jivamritham in plantations, but one can use smaller containers by simply reducing the ingredient ratios. The soup is stirred 3 times a day and is ready for use by the third day. The charcoal is simply immersed in the soup, allowing soil bacteria and other microfauna to saturate it. Once saturated (a few hours) mycorrhizzal fungi, compost or other goodies can be added, but basically we now have charged the charcoal and created biochar.

Making 200 tons of compost.
Not everyone has cows, so another popular charging agent is compost tea, made with compost, worm castings, sugars and water. There are a number of compost tea recipes available on the internet for home gardeners wishing to charge charcoal and create biochar. The home garden mix is usually 10% biochar to 90% compost. There are also recipes using sea weed (kelp), and even commercial fertilizers, though on principal any use of agrochemicals kind of defeats the purpose of using organic materials like biochar to improve the soil. Obviously, plantations need large scale, affordable solutions that are less labor intensive than a home gardener might employ. One of the best books available on composting is the Humanure Handbook by Joseph C. Jenkins, who describes in clear terms how best to make compost using human waste and other organic materials.

Fertilizer factory at La Pedregoza.
It is important to mention that biochar is best when reduced in size. Some biochar retorts are designed to work with wood chips. This means that crushing the charcoal afterwards is not necessary, but most retorts are based on turning larger chunks of wood, bamboo, corn or cane stalks and so on into charcoal, so the charcoal needs to be crushed before being charged. One simple method is to put the charcoal into canvas or vinyl bags and to then drive a truck, tractor or car over the bag, crushing the charcoal. Caution should be exercised when crushing charcoal, as one does not want workers to inhale the dust. The crushed charcoal is then charged, which means that one has a lot more surface area in the biochar to with soil bacteria, mycorrhizzal fungi and other microfauna can adhere.

Branch line is root extension of trees.
At Amazonia Reforestation and CO2 Tropical Trees the charged biochar is either tilled into the soil or mixed into slurry with clay and compost and then poured onto the soil. In existing tree cultivations a worker uses a spade to dig a quick hole beside each tree, into which one or two shovels of biochar mixed with compost are dumped and then covered up. Those holes should be right below the branch line of the trees, as that generally corresponds to where the tips of the trees’ roots will be located. As a rule of thumb, planters and foresters look to add at least 1 kg of biochar to every square meter, so in a one hectare woodlot (2.47 acres) that translates into 10,000 square meters, meaning that 10 tons of biochar would be required to enhance and improve the CEC of the soil.

Adding lime to soil is costly.
Now that we have found a solution to the problem of soil nutrient retention (the CEC), there remains the vexing problem of soil acidity in the tropics. While many native trees and plants are adapted to high soil acidity, many commercial tree species and agricultural plants are not. The traditional method to deal with this problem has been to add large amounts of dolomitic lime (Ca) to the soil, in order to balance the pH or make the pH more alkaline. This process can be fraught with problems as lime can kill soil microfauna, and severely burn plant roots. This means that foresters need to take a number of precautions when applying lime to the soil.

Cow urine has microelements.
The best method is to add the lime to the soil at least 4 weeks before one begins to plant. This allows the lime to filter into the soil, to be better distributed (after tilling or cultivating), to change the pH of the soil and to hopefully allow some recovery of the soil microfauna. It should be mentioned that there are some commercial lime preparations that are a little less harsh on the soil, such as Calfos, a mixture of dolomitic lime and phosphorus that acts as a kind of fertilizer at the same time. One benefit of lime in the soil is the fact that calcium (Ca) is essential for cell formation, so if one wants good plant growth, a certain amount of lime needs to be in the soil to stimulate and assist in cell formation as the tree is growing. 

The organic planter intent on implementing natural silviculture processes in a tropical tree plantation has another option to combat soil acidity. A by-product of making biochar is wood ashes. Wood ashes are a wonderful fertilizer, rich in all sorts of micro elements required for tree growth, and also rich in calcium. In fact, one can overdo wood ashes so care must be taken when they are added to the soil, but an immediate benefit is the fact that most of the micro elements in the ashes are more biologically available then those in commercial agrochemical mixes, and the alkalinity factor of wood ashes (pH of 10.4) is higher than that of lime (pH of 9.6). This means that using biochar retorts creates 2 products using local resources and eliminating transportation costs. Even better, as soil nutrient retention and microfauna increases and organic material starts to exist in the soil, this also reduces soil acidity. In Part 5, I will discuss and compare the difference between natural silviculture and agrochemicals and their impact on the soil, and explain why the soil has a soul that needs to be protected, as it is a vital component of biodiversity and a healthy planet.

© 2014 CorporaciĆ³n Ambiental La Pedregoza – All Rights Reserved

Thursday, January 9, 2014

Understanding Tropical Soils: Part 3

This article is continued from Understanding Tropical Soils: Part 1 and Part 2.
by Dexter B. Dombro

International Biochar Initiative
With the discovery of Terra Preta, many people want to implement biochar programs. This can be especially difficult on a large scale, but solutions are being developed all over the planet. Some of the examples given here are based on the methodology being developed at the Amazonia Reforestation and CO2 Tropical Trees La Pedregoza and El Encierro plantations in the Orinoco River basin of Vichada, Colombia, together with designs and solutions that have been developed by biochar enthusiasts worldwide. For more information I highly recommend checking out the International Biochar Initiative, of which I am a member.

Tree pruning produces a lot of biomass.
At La Pedregoza we have noticed that when pruning Acacia mangium cultivations, there are approximately 5 KG of branches and twigs being removed per tree. Since there are around 1,200 trees per hectare in an Acacia mangium plantation, this means that there is approximately 6 metric tons of woody biomass available per hectare (2.47 acres). Biomass from pruning at present has no ready markets, so this is a boon to planters, as the pruned material can be gathered and converted into biochar. Many other tree species produce similar results, and as mentioned before charcoal can be made from just about any vegetal matter.

Culled trees have various uses.
As trees mature in cultivations, the ones that are performing poorly are often culled to allow better growing trees to expand and to receive more light. Culling is also a way to better aerate a plantation, especially in wet tropical conditions. This culled woody biomass may have some economic value (fence posts, wood pellets, small boards etc.), but a lot of it can also be converted to biochar. Needless to say, biochar can also be sold to neighbors and others as a processed product. In hardware and garden centers around the world biochar packages for home gardeners can fetch significant prices, which help to support farmers and plantation owners. The point is that tree plantations and agricultural projects generally speaking have sufficient biomass available to implement biochar programs.

Decomposition is slow and releases GHG.
It should be mentioned that if the culled or pruned material is simply left to decompose on the ground, there may be some limited benefit to the soil. However, consider this: it takes many years for a large pruned branch to decompose. All the methane and co2 locked in the decomposing wood is released into the atmosphere, adding to greenhouse gases (GHG). While the biomass slowly converts into organic material, it does not become a retention agent, improving the soil’s CEC. This is why collecting it and converting it to biochar makes more economic and environmental sense.

Traditional charcoal making is inefficient.
Once the benefits of biochar were identified, people quickly realized that traditional methods of making charcoal are not really desirable. Traditional charcoal making involved pits filled with biomass or wood piles being burned and then doused at some point before all biomass is consumed. Unfortunately, this method has two large drawbacks. The first is that all greenhouse gases in the biomass are released into the atmosphere, which is completely undesirable. The second is that on average this method has a very poor 10 to 1 conversion rate, with one ton of biomass producing only 100 kg of charcoal. This makes it economically inefficient and wasteful. Unfortunately, it is the prevalent method of making charcoal in much of the developing world, and in some countries a leading cause of deforestation.

Adam Retort photo courtesy of Chris Adam
The best way of making biochar is to construct retort ovens that rely on pyrolysis or low oxygen burning to convert the biomass to charcoal. Retorts are basically sealed chambers inside ovens that allow the operator to control the pyrolysis burn in a low oxygen environment. The retort is packed with biomass and sealed so that very little oxygen can enter. Some biomass is placed inside the oven area and lit, so that it can start to heat up the retort. As the biomass inside the retort gets hot, it starts to release the greenhouse and volatile gases in the biomass, which are gathered and piped or ducted back down into the oven area, where they burn off while continuing to heat the retort. The biomass inside the retort chamber turns to charcoal. These ovens are environmentally friendly, can be built fairly cheaply using locally available resources and supplies, and have a much better conversion rate of 10 to 3.5, meaning for every 1 ton of biomass one can produce around 350 kg of charcoal.

At La Pedregoza we are in the process of constructing 3 large Adam Retorts, based on a design development by a German Ph.D. by the name of Chris Adam. Our goal is to produce on average 1 metric ton of charcoal per day and to then charge it with organic material so that we will have substantial biochar with which to improve our soils (see the soil sample in Part 1). In Part 4 of this series we will discuss the charging of the biochar and its application to the soil, as well as how best to use wood ashes, which are another by-product from making charcoal.

© 2014 CorporaciĆ³n Ambiental La Pedregoza – All Rights Reserved


Sunday, December 22, 2013

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.