The organically maintained landscape 2
The organically maintained landscape 2
The organically maintained landscape 2
The Organically MaintainedLandscape
In natural systems, organic matter generally cycles in place, added to the soil through root and stem decay of winter killed annuals and leaf decay. A thriving microbial community digests and breaks down this organic matter to release nutrients back to the soil. Organic soil amendments may be needed to help balance the soils chemistry, stimulate its biology, and restore its physical composition. Such amendments may also be needed to feed turfgrass in a lawn, which has extraordinary nutrient needs because it is grown in an unnatural way, perpetually mowed and kept green as long as possible.
NPK and Inorganic Fertilizers
Lawn and landscape care methods, which directly feed the plant with synthetic nitrogen-phosphorous-potassium (NPK) lead to damage to the soil and a weak root system, making the turfgrass or plants in the landscape more susceptible to insects, disease and drought. Over fertilizing the turfgrass or plant will also inhibit the development of mycorrhizae, a symbiotic fungi growing on or around the plant roots that help gather nutrients beyond the range of the root themselves. Eventually the soil structure collapses and becomes infertile.
Leaching
Like the negative end of a magnet, nitrogen in the form of nitrate is negatively charged and is not attracted to soil's negatively charged clay and humus. Negatively charged clay repels negatively charged nitrite (NO2) and nitrate (NO3) so they will not be absorbed by the clay and are left to move down through the soil and into the groundwater, where streams and drinking water can become contaminated.
Reviving collapsed soil structure
To revive dead, compacted soil, it will necessary to apply compost and compost tea to improve and build soil life.
A well-balanced soil fertility program that increases humus content, organic matter and beneficial microorganisms recycles nutrients, improves water retention, balances minerals and buffers PH. In addition to compost, organic matter (manure) and compost tea may be indicated based on soil test results. These include natural surfactants to aerate soil, root stimulants and developers, rock dust, secondary and micronutrients, flocculants, vitamins, beneficial microbes, enzymes, organic humus, fulvic acid, kelp and dextrose
What is nitrogen (N)
Nitrogen is an essential macronutrient because it is required to create amino acids and proteins, genetic material, chlorophyll and other important biochemical molecules. Nitrogen is the most abundant gas in the atmosphere (78%) but the gaseous form (N2) is inert and unavailable for use by animals and most plants. Turning N2 into available nitrogen or "fixing" it, requires breaking the bond between the nitrogen atoms, which requires energy. Under natural conditions, nitrogen is fixed by lightning strikes through the atmosphere and by the work of a few species of symbiotic bacteria and some free-living bacteria and fungi in the soil or water. As part of the symbiotic relationship, the plant subsequently converts the ammonium ion to nitrogen oxides and amino acids to form proteins and other biologically useful molecules, such as alkaloids. In return for the usable (fixed) nitrogen, the plant secretes sugars to the symbiotic bacteria.
What is Phosphorous? (P)
Phosphorous, in the form of phosphate, is an essential macronutrient it is a vital part of the cellular energy transfer. Phosphorous is added to soils in natural systems by rock weathering. Leaching and runoff removes phosphorous from the soils, where it is carried to aquatic systems like aquifers, streams, lakes and bays. In fresh water aquatic systems excess phosphorous can substantially increase plant productivity and lead to eutrophic conditions (lack of oxygen), causing increased phytoplankton and bacterial growth, loss of dissolved oxygen and loss of animal life in the system.
What is Potassium? (K)
It is primarily used in fertilizers as either the chloride, sulfate or carbonate not as the oxide. Potassium is an essential component needed in plant growth and is found in most soil types. Potassium has two roles in the functioning of plant cells. First, it has an irreplaceable part to play in the activation of enzymes, which are fundamental to metabolic processes, especially the production of proteins and sugars. Only small amounts of potassium are required for this biochemical function. Second, potassium is the "plant-preferred" ion for maintaining the water content and hence the turgor (rigidity) of each cell, a biophysical role. A large concentration of potassium in the cell sap creates conditions that cause water to move into the cell (osmosis) through the porous cell wall. Turgid cells maintain the leaf's vigor so that photosynthesis proceeds efficiently.
Plants are apparently unable to regulate the uptake of potassium; and if the soil supply is high enough, so-called luxury consumption may result. Under such conditions, the high potassium content in the grass plant may cause an excessive amount of stiffness in the stems and leaves as well as other undesirable or harmful effects.
NPK note: Commercial preparations of fertilizers have a somewhat misleading labeling system. It is often said that the three main numbers listed is the amount of Nitrogen, Phosphorus, and Potassium in the product. This is NOT the case. You must read the label carefully. If you read carefully, you will find that the last number is the percentage of Soluble Potash NOT Potassium expressed as K2O.
THE MYSTERY RATIO by Paul Tukey Here's something you won't hear from most soil testing agencies outside of the Soil Food Web: The relationship between calcium and magnesium is among the most important in lawn care.
For years, especially in the East where soils are inherently acidic, folks have applied limestone to raise the pH. Often times, that limestone has been dolomitic in nature, meaning it contains a high percentage of the heavy metal magnesium. Although soils do need magnesium to grow grass, too much magnesium will leave soils overly compacted. The result is often a high percentage of weeds.
If your soil test result from the Cooperative Extension Service tells you to add limestone at a specific rate, you will usually be better off adding high-calcium or "calcitic" limestone rather than dolomitic limestone. In soil, the ideal ratio is seven times more calcium than magnesium. Since calcium moves through the soil slowly, it is almost impossible to add too much.
Organic Matter
Natural organic material is classified into two categories according to their carbon and nitrogen content: Green organic material and Brown organic material.
"Green" materials, such as fresh grass clippings, manure and other living plants (weeds) and plant products contain large amounts of nitrogen.
"Brown" materials such as dried leaves and plants, branches, and woody materials (leaf stems) have high carbon content but are relatively low in nitrogen.
Basically, "Green" materials supply food for the biolife (bacteria, fungi, and small invertebrates such as worms) which intern manufacture, supply, and facilitate nutrient uptake for the plants. The "Brown" materials provide a home for the "Green" material biolife. When both "Green" and "Brown" organic materials decompose they become organic matter or "Humus"
The "Brown" to "Green" ratio should be15:1 to 20:1 for a healthy lawn.
Characteristics of good quality soil
Appearance Few recognizable components of original material remain. Structure is light and crumbly.
Color - Dark brown to black
Texture or particle size Fine texture, particles smaller than 1/2 inch for incorporation, smaller than 1/8 for topdressing.
Odor Earthy aroma, no smell of ammonia or sulfur.
Temperature Not warm to the touch.
Moisture content 30 to 50%
Carbon to nitrogen ratio (C:N ratio) 15:1 to 20:1
Organic Matter %
Natural organic material is classified into two categories according to their carbon and nitrogen content: Green organic material and Brown organic material.
"Green" materials, such as fresh grass clippings, manure and other living plants (weeds) and plant products contain large amounts of nitrogen.
"Brown" materials such as dried leaves and plants, branches, and woody materials (leaf stems) have high carbon content but are relatively low in nitrogen.
Basically, "Green" materials supply food for the biolife (bacteria, fungi, and small invertebrates such as worms) which intern manufacture, supply, and facilitate nutrient uptake for the plants. The "Brown" materials provide a home for the "Green" material biolife. When both "Green" and "Brown" organic materials decompose they become organic matter or "Humus"
Lawn Soil and the Importance of Biolife
Most soils are teeming with life microbial life that is as important to our lives as the more visible flora and fauna we see around us. Just imagine if there were no decomposers in the soil. In a matter of years, we would be buried in organic debris that no longer breaks down. Nutrient cycles would grind to a halt and plants would not survive without our constant feeding. And soil microbes have been the source of life-saving compounds such as antibiotics (e.g. penicillin) that we have come to rely on.
As small as they are, soil microorganisms are the real giants in your lawn, and your lawn soil is swarming with millions of these microorganisms. This "living-soil-life" helps keep your soil healthy, decompose organic matter, replenish soil nutrients, form humus, store and regulate water, promote root growth, increase nutrient uptake, and (over time) the breakdown of herbicides and pesticides. These microorganisms include bacteria, fungi, and protozoa.
Bacteria - What bacteria lack in size, they make up in numbers. They are tiny, one-celled organisms. A teaspoon of productive soil generally contains between 100 million and 1 billion bacteria.
Bacteria have four functional groups.
1. Most are decomposers that consume simple carbon compounds. By this process, they convert energy in soil organic matter into forms useful to the rest of the organisms. A number of decomposers, over time, can break down pesticides and pollutants in soil. Decomposers are especially important in stopping or retaining, nutrients in their cells, thus preventing the loss of nutrients, such as nitrogen, from the rooting zone.
2. A second group is the mutualists that form partnerships with plants. The most well-known of these are the nitrogen-fixing bacteria.
3. The third group is the pathogens.
4. A fourth group, called lithotrophs (literally meaning rock eaters) or chemoautotrophs (which are able to synthesize all of the organic compounds they need from inorganic raw materials in the absence of sunlight), obtains its energy from compounds of nitrogen, sulfur, iron or hydrogen instead of from carbon compounds.
Functions
They perform important services related to water dynamics.
nutrient cycling
Disease suppression.
Many organisms will compete with disease-causing organisms in roots and on aboveground surfaces of plants.
Important Bacteria
Nitrogen-fixing The plant supplies simple carbon compounds to the bacteria, and it converts nitrogen (N2) from air into a form the plant host can use. When leaves or roots from the host plant decompose, soil nitrogen increases in the surrounding area.
Nitrifying change ammonium to nitrite then to nitrate a preferred form of nitrogen for grasses and most row crops.
Denitrifying convert nitrate to nitrogen (N2) or nitrous oxide (N2O) gas. Denitrifiers are anaerobic, meaning they are active where oxygen is absent, such as in saturated soils or inside soil aggregates.
Actinomycetes are a large group of bacteria that grow as hyphae like fungi. They are responsible for the characteristically "earthy" smell of freshly turned, healthy soil. Actinomycetes decompose a wide array of hard-to-decompose compounds and are active at high pH levels. A number of antibiotics are produced by Actinomycetes such as Streptomyces.
Fungi Basically there are two types of fungi Mycorrhizaland normal. Fungi thrive in well-drained, neutral to acidic, aerated soils. Normal fungi help decompose the organic matter in litter and soil but play less of an overall role. Mycorrhizal fungi help develop healthy root systems by growing on plant roots. The fungus is actually a network of filaments that grow in and around the plant root cells, forming a mass that extends considerably beyond the plant's root system. This essentially extends the plant's reach to water and nutrients, allowing it to utilize more of the soil's resources.
Protozoa These microorganisms are present in almost all soils. They feed on bacteria and other protozoa. Protozoa are classified into three types based on their mobility: Amoebae, Flagellates, and Ciliates. Good protozoa feed on bacteria and release nitrogen and other nutrients to the soil. Since they live in and around roots the plants benefit from this supply of food.
Protozoa are a major part of the living soil.
Protozoa are single-celled animals that feed on bacteria, other protozoa, organic matter, and sometimes fungi.
They are several times larger than bacteria.
The numbers of protozoa in the soil vary from a 1,000 per teaspoon in unfertile soils to a 1,000,000 per teaspoon in some fertile soils.
Protozoa are divided into three groups based on their shape:
1. Ciliates
Are the largest of the protozoa and are mobile by means of hair-like cilia.
They eat the other two types of protozoa, also bacteria.
They eat up to 10,000 bacteria per day, and make nitrogen available to plants.
Ciliates are least numerous of the 3 groups.
Ciliates move rapidly through soil using the cilias like boat oars.
2. Amoebae
They can be large and they move by means of a pseudopod.
Amoebae are divided into testate amoebae and naked amoebae.
One group of amoebae, like vampires, eat fungi and root pathogens.
3. Flagellates
They are the smallest of the protozoa and use whip-like flagella to propel or pull its way through soil.
Functions of Protozoa
1. Protozoa help mineralize nutrients, which make them available for use by plants and other soil organisms.
2. Protozoa regulate bacteria populations as they graze on bacteria and it seems to stimulate growth of that bacterial population.
3. Protozoa is a food source for other soil organisms.
4. They help to suppress disease by feeding on pathogens.
5. Protozoa release excess nitrogen as they eat bacteria that will then be used by plants and other members of the food web.
Fungi
A gram of garden soil can contain around one million fungi, such as yeasts and molds. Fungi have no chlorophyll, and are not able to photosynthesize; besides, they can't use atmospheric carbon dioxide as a source of carbon, therefore they are chemo-heterotrophic, meaning that, like animals, they require a chemical source of energy rather than being able to use light as an energy source, as well as organic substrates to get carbon for growth and development.
Many fungi are parasitic, often causing disease to their living host plant, although some have beneficial relationships with living plants as we shall see below. In terms of soil and humus creation, the most important fungi tend to be saprotrophic, that is, they live on dead or decaying organic matter, thus breaking it down and converting it to forms that are available to the higher plants. A succession of fungi species will colonize the dead matter, beginning with those that use sugars and starches, which are succeeded by those that are able to break down cellulose and lignin's.
Fungi spread underground by sending long thin threads known as mycelium throughout the soil; these threads can be observed throughout many soils and compost heaps. From the mycelia the fungi is able to throw up its fruiting bodies, the visible part above the soil (e.g., mushrooms, toadstools and puffballs), which may contain millions of spores. When the fruiting body bursts, these spores are dispersed through the air to settle in fresh environments, and are able to lie dormant for years until the right conditions for their activation arise or the right food is made available.
Steve
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