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Jeff Lowenfels called out, was "Grass in shade"
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, gardengal wrote: On Apr 4, 10:22Â*am, Billy wrote: In article , Â*gardengal wrote: Plants do not make soil acidic - acid soils occur as a result of the mineral content and amount of rainfall. AAAAAAAAAAh - wrong All nitrogen is not the same Ultimately, from the plant's perspective anyhow, the role of the soil food web is to cycle down nutrients until they become temporarily immobilized in the bodies of bacteria and fungi and then mineralized. The most important of these nutrients is nitrogen‹the basic building block of amino acids and, therefore, life. The biomass of fungi and bacteria (that is, the total amount of each in the soil) determines, for the most part, the amount of nitrogen that is readily available for plant use. It wasn't until the 1980s that soil scientists could accurately measure the amount of bacteria and fungi in soils. Dr. Elaine Ingham at Oregon State University along with others started publishing research that showed the ratio of these two organisms in various types of soil. In general, the least disturbed soils (those that supported old growth timber) had far more fungi than bacteria, while disturbed soils (rototilled soil, for example) had far more bacteria than fungi. These and later studies show that agricultural soils have a fungal to bacterial biomass (F:B ratio) of 1:1 or less, while forest soils have ten times or more fungi than bacteria. Ingham and some of her graduate students at OSU also noticed a correla- tion between plants and their preference for soils that were fungally dominated versus those that were bacterially dominated or neutral. Since the path from bacterial to fungal domination in soils follows the general course of plant succession, it became easy to predict what type of soil particular plants preferred by noting where they came from. In general, perennials, trees, and shrubs prefer fungally dominated soils, while annuals, grasses, and vegetables prefer soils dominated by bacteria. One implication of these findings, for the gardener, has to do with the nitrogen in bacteria and fungi. Remember, this is what the soil food web means to a plant: when these organisms are eaten, some of the nitrogen is retained by the eater, but much of it is released as waste in the form of plant-available ammonium (NH^). Depending on the soil environment, this can either remain as ammonium or be converted into nitrate (NO,) by special bacteria. When does this conversion occur? When ammonium is released in soils that are dominated by bacteria. This is because such soils generally have an alkaline pH (thanks to bacterial bioslime), which encourages the nitrogen-fixing bacteria to thrive. The acids produced by fungi, as they begin to dominate, lower the pH and greatly reduce the amount of these bacteria. In fungally dominated soils, much of the nitrogen remains in ammonium form. Ah, here is the rub: chemical fertilizers provide plants with nitrogen, but most do so in the form of nitrates (NO,,). An understanding of the soil food web makes it clear, however, that plants that prefer fungally dominated soils ultimately won't flourish on a diet of nitrates. Knowing this can make a great deal of difference in the way you manage your gardens and yard. If you can cause either fungi or bacteria to dominate, or provide an equal mix (and you can ‹ just how is explained in Part 2) , then plants can get the kind of nitrogen they prefer, without chemicals, and thrive. p 25 -26 Teaming with Microbes: A Gardener's Guide to the Soil Food Web by Jeff Lowenfels, Wayne Lewis Â* Â*€ Â*Publisher: Timber Press, Incorporated (July 15, 2006) Â* Â*€ Â*ISBN-10: 0881927775 Â* Â*€ Â*ISBN-13: 978-0881927771 -- - Billy "For the first time in the history of the world, every human being is now subjected to contact with dangerous chemicals, from the moment of conception until death." Â*- Rachel Carson http://www.youtube.com/watch?v=WI29wVQN8Go http://www.haaretz.com/hasen/spages/1072040.html God, you're a bit of an irritant, aren't you? You ain't seen nothin' yet ;O) If you had done any serious study of soils aside from only reading what has been written by others, you would know that what I wrote is entirely correct. Plant life and soil microbial content has only a minimal impact on unamended soil pH. Soil pH is dependent primarily on the two factors I stated - the native mineral content of the soil and the amount of rainfall it receives. Areas of high rainfall tend to have acidic soils; arid locations tend towards alkalinity. Plants that grow in acidic soils did not create that situation nor do they make them more so - that's mistaking representation for causation. Plants grow in acidic or alkline soils because that is to their liking. Oak trees don't create acidic soil - they grow in acidic soil because that is their preference. Acidic plant debris on the surface of the soil can create a slightly lower pH on that surface, but it does not penetrate to any significant depth into the soil strata. The amount of organic matter one adds through incorporation - not just lying on the soil surface - to a soil can lower pH but it would take considerable quantities to affect any significant change. That's why it is recommended to add minerals - sulfur or lime - NOT organic matter or other plant life to alter a soil's natural pH. "The parent material of soils initially influences soil pH. For example, granitic soils are acidic and limestone-based soils are alkaline. However, soil pH can change over time. Soils become acidic through natural processes as well as human activities. Rainfall and irrigation control the pH of most soils. In humid climates, such as the northeastern United States, heavy rainfall percolates through the soil. When it does, it leaches basic ions such as calcium and magnesium and replaces them with acidic ions such as hydrogen and aluminum. In arid regions of the country (less than 20 inches of rain per year), soils tend to become alkaline. Rainfall is not heavy enough to leach basic ions from soils in these areas. Other natural processes that increase soil acidity include root growth and decay of organic matter by soil microorganisms. Whereas the decay of organic matter gradually will increase acidity, adding sources of organic matter with high pH values (such as some manures and composts) can raise soil pH. Human activities that increase soil acidity include fertilization with ammonium-containing fertilizers and production of industrial by- products such as sulfur dioxide and nitric acid, which ultimately enter the soil via rainfall. Irrigating with water high in bicarbonates gradually increases soil pH and can lead to alkaline conditions. In most cases, changes in soil pH, whether natural processes or human activities cause them, occur slowly. This is due to the tremendous buffering capacity (resistance to change in pH) of most mineral soils." Thanks for keeping it simple. Soooo, basically what you are sayin' is that Jeff Lowenfels and his book are full of crap, not worth buying, and that plant exudates have nothing to do with soil pH. Is that about it? What may be your credentials be to to impugn Mr. Lownfels, besides dirty finger nails, i.e. what is the basis of your authority, so that we can all be properly impressed? http://home.gci.net/~jeff/gardener/ Have a really good day ;O) -- - Billy "For the first time in the history of the world, every human being is now subjected to contact with dangerous chemicals, from the moment of conception until death." - Rachel Carson http://www.youtube.com/watch?v=WI29wVQN8Go http://www.haaretz.com/hasen/spages/1072040.html |
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