| Dr.
Paul's Research Perspectives By Paul Hepperly |
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My last column included a photo of an underweight baby. The sadness of this malnourished child is a cry to the soil, for it is the soil that feeds the mother and the mother that feeds the child. Our health ultimately depends on the health and fertility of the soil we steward. Traditional agriculturists understand that soil is the most important aspect of crop support. The earth nurtures plants just as a mother nurtures her child. Reliance on synthetic fertilizers, on the other hand, sacrifices soil (the mother) by seeking to feed the crop (or child) directly. Feeding the mother will automatically care for the child. In talking about composting to extension agents in Ghana, my goal was to include scientific information while concentrating on practical, traditional African composting methods. Composting aligns well with traditionally held values in Ghana, and I emphasized that it was an honored task, practiced by their forefathers. As we assembled our compost pits, we enlisted the help and support of the neighboring villagers. When we finished, we gathered in a circle around the pile and I asked the participants to join hands. Be grateful for a kind mother who nurtures grateful hearts; this feeds our soul. Show your gratefulness to the source of life by recognizing Earth as the Mother and taking care of Her. We promised to share the bounty of the compost. Then I asked each participant to press his or her hand into the pile. This represented how each of us had put their hands and hearts into this project. The hand is the gateway to the heart when our labor represents our heartfelt emotions. These sentiments feed the living compost on the nonphysical level. Tropical soils: Challenges and opportunities As I mentioned last time, about two-thirds of the world's tropical soils are red acid soils, notoriously low in plant nutrients. In Ghana, red acid soils constitute about 80 percent of the soil base, and farmers complain that it is getting harder and harder to wrest productivity from the land. Improving agricultural productivity in Ghana and other tropical areas clearly depends on improving management of red acid soils.
In a previous column I wrote about the ‘terra preta do Indio,’ or Indian black soils. These intriguing soils are derived from red acid oxisols and ultisols, the oldest and generally least fertile of all soil families. Unlike their parent soils, however, the Indian black soils are extremely productive, and demonstrate the great potential for transforming red acid soils by increasing their soil organic matter content. Although we see eroding and deteriorating soils in many parts of the world, we can take heart because not only can this be stopped, it can even be reversed under what appear to be the most limiting of conditions. This is the essence of Robert Rodale’s concept of regenerative agriculture. Regenerative agriculture is partly inspired by Sir Albert Howard’s experience working with impoverished red acid tropical soils in British colonial India. Modern windrow composting is a variation on the "Indore Compost Method," refined by Sir Albert from ancient Indian composting practices. In Africa, we need to go beyond sustainable agriculture because with the present poor resource base we will not be able to feed the growing population just by being sustainable. Instead, we need to re-capacitate or regenerate soils, farms, and communities. Sir Albert called this the Law of Return--we must feed the soil properly if it is to feed us properly. The Rodale Institute® farm in Kutztown, Pennsylvania, was founded on worn-out agricultural soils that have now been regenerated. Through organic farming methods such as the use of compost, cover cropping and rotations we have not only sustained a thin, perishable soil layer but built it to a point where we routinely surpass neighboring conventional yields. Some soil scientists dismiss acid red tropical soils as being incorrigibly unproductive. But these soils do have valuable qualities: in general, they are deep, well drained and can be worked with machinery shortly after heavy rains. Just as we cannot afford to have children left behind in their educational experience, we definitely need to "leave no soil behind" in the effort to support our growing world population. From an agricultural development perspective, the question should be: How do we most effectively convert acid red soils into black, fertile soils? To a large extent, the answer is, by boosting organic matter levels through the use of compost. Organic matter neutralizes constraints of acid soils Red acid soils exhibit both low fertility and potential toxicity to plants. An acid red soil lacking in soil organic matter can solubilize large amounts of metals, notably aluminum and manganese. When these metallic ions dominate the soil solution, they block the absorption and activity of essential nutrients such as calcium, resulting in reduced yields or even crop failure.
As the organic matter and clay complexes form, aluminum ions are pulled out of the soil solution. Once aluminum is captured in an insoluble complex of clay and organic matter, calcium absorption and movement in the plant roots and tops is no longer impeded. Besides eliminating nutrient interference, soil organic matter itself serves as a rich source of nutrients for plant growth. Organic matter works to expand the nutritional support potential of the soil, fostering more optimum plant growth. It also allows more water to penetrate the soil and remain there to be taken up by plants. A soil optimized in organic matter helps protect plants from periodic drought. Aluminum toxicity
When plants develop aluminum toxicity in an acid soil environment, they look like someone cut off their root tips. The condition is called terminal deficiency because it affects the outermost cells and tissues. Blossom-end rot in tomatoes is a form of terminal deficiency. (In humans the effects of insufficient calcium are as dramatic as in plants--the breakdown of bone structure called osteoporosis.) Tip necrosis due to insufficient calcium can result from the use of ammoniated fertilizer or prevented by calcium fertilization. Acidity from ammoniated fertilizers drives aluminum ions into solution, interfering with calcium uptake and movement in plants. Adding calcium can take aluminum out of solution and serve as a direct source for plant nutrition. Calcium salts provided to the plant through foliar applications, however, will have no effect on root health, because calcium only moves upward within plant tissue. Calcium plays many crucial roles in plant physiology, including bridging and linking cells by interacting at cell walls and membranes. Water availability, in turn, is critical to the movement of calcium within plants--fluctuating water stress predisposes plants to blossom-end rot. Soil organic matter, with its ability to buffer water fluctuations, plays an important role in preventing water stress. Although a calcium salt solution can remedy both aluminum toxicity and calcium deficiency, calcium salts cannot help soil percolate or hold water the way organic matter does. Knowing this, we can understand aluminum toxicity as an induced calcium deficiency that can be resolved by organic matter. Organic matter is the bulwark of soil, maintaining both proper moisture availability and aeration. No chemical salt can substitute for these functions. From all of these perspectives, soil improvement with optimized organic matter makes sense. Salts can in some instances remedy the symptoms of soil infertility, but they provide none of the long-term benefits of increased soil organic matter. Black organic matter is the real green revolution Conventional ammoniated fertilizers exacerbate existing soil acidity. Ammoniated fertilizer does not feed soil organic matter but instead stimulates decomposition, resulting in lower soil organic matter content. The nitrogen component of conventional fertilizer has no duration from season to season and requires similar or greater applications for every crop, every season.
The Rodale Institute's Compost Utilization Trial compared the effects of fertilizer, raw manure and compost on crop productivity, soil health, and environmental quality. Interestingly, although all approaches were equally effective in optimizing crop productivity, compost was the only approach that also improved soil health and environmental quality. Compost improved soil organic matter and nitrogen levels while simultaneously lowering nutrient losses to ground and surface water. Compost also increased crop nutrient content. Fortunately, composting is a traditional technology practiced throughout the developing world. In Africa there is little infrastructure to support widespread liming and other conventional agriculture approaches by small farmers. As a result, concentrating on fertilizer “solutions” leads to the problem Ghana's small farmers complain about: poor soils becoming worse. Raising soil organic matter opens the soil texture, allowing both air and water to penetrate and stimulating soil microbial life. In The Rodale Institute Farming Systems Trial, we have found that improved soil organic matter levels can increase water penetration by as much as 50 percent. This contributes to the ability of plants to make do on limited water supplies. In many developing areas, including northern Ghana, water is not optimized and improving the soil is the best way to stabilize crop productivity. As natural materials, soil organic matter and compost are very complex in their composition and action. This complexity intrigues and confuses scientists. There is no formula for humic material; rather it exists as a mixed class of an infinite number of compounds, representing a wide array of biological products from diverse organisms and defying chemical definition. "Man no be God"—and neither is science
In the Western scientific method, a lot of emphasis is given to how things work, their mechanism of action. The biological processes at work in organic agricultural systems, however, are much more complex than the simple actions of chemical salts. If we limit ourselves to interacting only with things we completely understand, we are left with a poor set of tools indeed. Often, the things we do not understand are more powerful than the things we do understand. Many Western scientists simply do not want to deal with things they don’t understand. Traditional knowledge allows for a more humble approach, basing practice on experience even when the mode of action is not completely understood. It would be most unfortunate to select technologies of lesser potential because we believe we understand them better. Rather than take that limited track, we should put more effort on traditional processes, which offer more even though they are less well understood. Western technology is extremely powerful, but it should complement indigenous knowledge, not replace it. Western scientific methods need to be tempered by ethics, or the technological result will ultimately be sterile. Modern insecticides and fertilizers are examples of sterile technologies. Both are also extensions of war technologies. The fact that we understand precisely how they work does not obscure the fact that they were designed to kill. We need values to reverse the problems we have created with such technologies. One of my favorite things I saw while I was in Ghana was a sign on the side of a passenger van that read, “Man no be God.” When man uses technology in self-serving and destructive ways, he takes an ignorant and egotistical approach. An unfortunate side effect of scientific endeavor is egoistical thinking. Frequently, we know less about our actions and how they affect natural balances than we think. As we eliminate pesky insects, for instance, we also eliminate pollinators and other beneficial organisms. Basing our crop production systems on poisons and attempting to replace the soil life force with simple chemical salts are perfect examples of science and technology running amok. The Hippocratic Oath enjoins physicians to "first, do no harm." Agronomists and other crop advisors should observe a similar rule. Even many advocates of chemically intensive agriculture now understand that substantial damage is being done to the environment. It is better for us to work with nature and be aware of its greatness. By casting life as the enemy, we set up a conflict against ourselves, for we are part of the web of life. In truth, we will "win" only if nature prevails, and we fall short of our goals. Previous: Teaching
composting for soil improvement in northern Ghana In the first
of this series, Paul describes a three-week volunteer effort to
help West African villagers learn about organic farming methods
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