By Dr. Elaine Ingham, Rodale Institute Chief Scientist The following article is from a presentation that Dr. Ingham gave at the Shumei Natural Agriculture Conference on January 21, 2012, at Shumei Hall in Pasadena, In March of 2011, just after starting as chief scientist at Rodale Institute, I toured the Shumei garden at the Institute and began to understand the principles that embody Natural Agriculture. ***** It was wonderfully enlightening to find people who share a similar attitude that natural processes must be the basis for agriculture.***** My expertise is focused on the organisms that exist in soil, and the processes these organisms perform. ++++ Looking at what happens to these organisms in current “conventional” agricultural systems is extremely depressing.++++ We need to understand what life is necessary in soil, how these organisms function, and what conditions must be present for soil organisms to perform their beneficial jobs. The more we maintain the proper conditions for the workers in the soil, the better we mimic nature and the higher the quality of our foods. Conventional agriculture does things differently than the way things are done in natural systems. We need to understand how those differences influence and affect the soil, plants and the quality of plants. We need to understand the damage conventional practices cause. We need to learn how to maintain our plant production systems as naturally as possible, realizing that ****short term gain in yields costs too much to the long–term health and balance of the system.**** What are the constraints we impose? What are the sets of organisms that need to be there? How do these organisms behave in a natural system and how we can use them in our agricultural systems? The Soil Food Web The soil food web is comprised of the different organism groups in soil: bacteria, fungi (including mycorrhizal fungi), protozoa, nematodes, microarthropods, and larger organisms. These organisms interact to perform the functions needed by plants in the soil: disease suppression (around roots and around above-ground parts of plants), nutrient retention (so loss of nutrients through leaching does not occur), nutrient cycling (making nutrients available to plants in the root zone), decomposition of waste materials, and building of soil structure so roots can grow as deep as the plant requires. Food web structure varies with season, climate, soil type, age of the ecosystem, etc. The existing food web will select for the growth of certain plants, and against the growth of others. Thus, defining health of the soil must be done relative to the desired plant. Is this food web healthy for this plant? To promote health, we need to understand soil as nature designed it. Plants have existed on this planet for at least the last billion years, meaning that the linkage between certain plants being selected by certain sets of organisms in the soil, and vice versa, has had plenty of time to develop. To understand this system, then, we need to start at the beginning. The process of photosynthesis in plants uses sunlight energy to bond carbon molecules together and form sugars. Plants store sunlight energy by bonding one carbon, from one carbon dioxide molecule, with another carbon from a second carbon dioxide molecule. Depending on what the plant needs, and its physiology, additional carbons can be bonded to the chain, storing energy in that sugar for future use. The sugar formed can be used to grow the plant, or it can be sent to the root system to escort nitrogen, in the form of an amino acid, or protein, for example, to where the plant needs it. These sugars will bond with phosphorus, sulfur, magnesium, calcium, potassium, sodium, or any other nutrient in order to move those nutrients to where the plant needs that nutrient to continue growing. All nutrients, except CO2 and sunlight, are provided to the plant through the soil. Soluble, inorganic forms of nutrients move into the plant by simple diffusion into the roots, but the inorganic nutrients have to be converted from the ionic form into carbon–bound forms once inside the root in order to prevent harm to the plant. Thus, once the soluble nutrient is inside the root, the plant uses enzymes to attach the nutrients to the carbon backbone of sugar from photosynthesis. How many necessary nutrients are required for plants to grow? When I was a child, scientists talked about only three necessary nutrients: nitrogen, phosphorus, and potassium, or NPK. All that was needed to grow a plant, right? Wrong! By the time I was in high school, scientists realized more than NPK was needed to grow a plant. By then it was twelve important nutrients, including Na, S, Ca, Mg, B, C, O, Fe, and Zn. By the time I was in graduate school, the number of important nutrients jumped from 12 to 18. Today, scientists would say 42. And will we discover more necessary nutrients? Probably. Science continues to discover more essential nutrients all the time. In fact, probably all of the nutrients found in soil are necessary in some amount. Consider the fact that all the nutrients plants need are found in soil. They are present in excess in the rocks, pebbles, and particles of sand, silt, clay, and organic matter. Inorganic fertilizers are not needed, as the farmers and horticulturalists of Shumei Natural Agriculture have taught for many years. It is the organisms in soil that convert those nutrients in the sand, silt, clay, rocks, and pebbles from non-available forms into plant-available nutrients. It is critical to have the organisms that perform these jobs present in adequate number, and balance, to be able to grow healthy plants. If the beneficial organisms in soil are killed through inappropriate management, plants cannot get mineral nutrients from the soil. If plants can’t get mineral nutrients, then they will either die, or humans will have to take over providing those nutrients as inorganic fertilizers. Humans are not good at knowing what inorganic nutrients plants require at any given instant, and so we put on too much, in the wrong places, at the wrong times, and soil is harmed even more. Those excess nutrients also leach out of the soil and destroy soil further down the hill. Ultimately those excess inorganic nutrients harm water and destroy the quality of our ecosystems all the way to the ocean. All agricultural soils, from young soil to ancient soil, contain all the nutrients needed to grow plants. If your plants show signs of poor fertility, what are lacking are the organisms that change the nutrients present in the soil from a plant-unavailable form into a plant-available form. What you lack is the biology, the organisms, to convert the nutrients that are present in your soil into a form of nutrient your plant can use. We need to have a full diversity of all these organisms in our soil. Each group of organism performs different basic functions. Disease, insect pests and weeds are all messages from nature trying to tell you exactly what’s present or missing in your soil; they are signs that you do not have the right sets of organisms present in your soil. People who want to sell you a product suggest you pick up a toxic chemical to kill the pest or disease, or to fix the lack of nutrient. Neither of these chemical approaches fixes the problem in a sustainable fashion. Use a chemical and most likely you will need to use more chemicals. Perfect for the salesman. Not so good for your soil, your health or your pocketbook.
Posted on: Thu, 25 Jul 2013 13:25:13 +0000
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