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Soil conditions typical in New York City yards are not ideal for growing plants and turf. In most cases the soil was brought in after houses were built, and it was put down in a thin layer over construction fill material. This soil tends to be compact with little or no organic matter.
These "hostile" conditions make it difficult for plants and lawn to get the water and nutrients needed for healthy, sustainable, green growth. Applications of quick-release chemical fertilizers, pesticides, and herbicides only further stress the plants and turf—making them more susceptible to the very things you are trying to prevent or cure.
Leaving grass clippings on the lawn returns much-needed organic material and water back to the soil. Here's more information to help you to practice preventative medicine in your yard by maintaining good soil health:
what
is soil
simple soil test
healthy soil structure
quitting chemicals
compost & aggregates
compost & nutrients
compost & soil pH
compost & soil ecology
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Soil is an incredibly complex, biologically and chemically active substance. While we often tend to think of it as "just dirt"—inert, lifeless stuff—soil is literally alive! It is estimated that there are more microbes in a teaspoon of soil than there are people on earth. Roughly speaking, soil is made up of minerals, air, water, and organic matter. The majority of soil is made up of rocks that have been pulverized over time into either sand, silt, or clay. This mineral portion of soil can vary with different percentages of these three components. In general here in New York City, the soil in Brooklyn and Queens tends to be sandy in the south, moving to more clay in the northern section of the boroughs. Staten Island soils are sandy about a mile in from the shore, at which point they exhibit a very high clay content. It is important to know your soil's components in order to adjust the pH or add appropriate nutrients.
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To get an idea of what your soil profile looks like, take a handful or small shovelful of soil and place it in a glass jar with a lid. Add water to about one inch from the top and shake. Allow the jar of soil and water to sit for a day or two. The soil will settle into its components, with sand on the bottom, followed by silt, then clay, and then the organic matter. Knowing the amounts of clay versus sand will be useful when determining liming needs to adjust the soil pH. Organic matter should ideally be 5% to 15% of the total. This organic portion of soil is typically eroded away, however, and needs to be replenished.
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The air and water your soil holds depends on the porosity of the soil. Soil that is healthy has a good physical structure (sometimes called tilth), which determines its ability to drain well, store moisture, and provide for the needs of healthy plants. Well-structured soil has lots of small aggregates and stays loose and easy to cultivate. Aggregates are groups of particles loosely bound together by the secretions of worms and bacteria. In between and within the aggregates themselves are many small air channels (or pores) like the empty spaces left in a jar of marbles. The channels that aggregates create in the soil allow plant roots and moisture to penetrate easily. The smaller pores within the aggregates loosely hold moisture until a plant needs it. The larger pore spaces between the aggregates allow excess water to drain out and air to circulate and warm the soil. The organic portion of the soil is the result of the decomposition of grass clippings, bits of leaves, and dead bugs. Humus is the generic term for this substance, whose characteristics can vary widely depending on what the original material was and how it decomposed. Humus is the main component of compost and is generally dark brown, porous, spongy, and pleasantly earthy-smelling. This decaying matter provides nutrients to the living microscopic organisms which have the primary responsibility of maintaining the balance of soil's chemical and ecological properties.
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Microbial action in soil makes nutrients available to the roots of plants and turf. Without soil microbes the only way to feed lawns is by the action of water-soluble, chemical fertilizers. These fertilizers provide a quick one-shot fix that must be repeated several times over the growing season. If you restore the microbial life of the soil and apply slow-released organic fertilizers, you will need to only fertilize once—in the fall, and you will break the chemical habit. If you currently apply pesticides or synthetic fertilizers, or have hired a lawn-care company to do so, you are spending your hard-earned money to support the "cravings" of a chemically-dependent lawn. While a chemically addicted lawn appears on the surface to be lush and green, is really a sterile system supported not by living soil and beneficial organisms, but by man-made chemical concoctions. Eliminate chemicals that kill beneficial organisms in the soil, and your lawn will gradually begin to thrive. For a few seasons, however, your lawn may exhibit some symptoms of withdrawal. During this transition from dependence to self-sustenance, you'll have to patiently nurture your recovering lawn. See links to organic farming and pest-control resources.
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By encouraging the formation of aggregates, compost improves the structure of every type of soil: silt, sand, or clay. In loose, sandy soils, compost helps to bind unconsolidated particles together to retain water and nutrients that would normally wash right through. Added to a clay or silt soil, compost breaks up the small, tightly bound particles and forms larger aggregates. This allows water to drain and air to penetrate.
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Compost contains a variety of the basic nutrients that plants require for healthy growth, including micronutrients such as iron, manganese, copper, and zinc. They are only needed in small doses, like vitamins in our diet, but without them plants have difficulty extracting nutrients from other foods. Micronutrients are often absent from commercial fertilizers, so compost is an essential dietary supplement in any soil. Compost also contains small amounts of the macronutrients that plants need in larger doses, including nitrogen, phosphorous, and potassium (the three numbers listed on fertilizer bags), and calcium and magnesium. Although compost generally contains small amounts of macronutrients, they are typically present in forms that may not be immediately available to plants. Due to the variable content and slow release of major nutrients in compost, it is often considered a supplement to fertilizers that contain more readily available nutrient sources. However, when applied in 3- to 5-inch layers over a period of years, compost may provide significant amounts of these nutrients and additional fertilizers may not be necessary.
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Because compost is primarily composed of humus, its structure too is made up of many aggregates. On a microscopic level, compost has vast surfaces inside these particles where individual ions of minerals and fertilizers can cling. Compost is able to store nutrients that might otherwise wash through a sandy soil or be locked up in the tight spaces of a clay soil. These ions are given up to the roots as plants require them. The ions clinging to the surfaces of compost particles tend to be those that give soil an optimum "neutral" pH range of 5.5 to 7.5. 
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Another beneficial characteristic of compost is the presence of compost organisms—redworms, centipedes, sow bugs, and others. The presence of decomposer organisms means that some organic material is still being slowly broken down and releasing nutrients. The decomposers are also indicators of a balanced soil ecology, which includes organisms that keep diseases and pests in check. Many experiments have shown that the rich soil life in compost helps to control diseases and pests that might otherwise overrun a more sterile soil lacking natural checks against their population. |
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For more
information, see:
• compost science
• using your compost
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