Compost.
Publié le 06/12/2021
Extrait du document
Ci-dessous un extrait traitant le sujet : Compost.. Ce document contient 1064 mots. Pour le télécharger en entier, envoyez-nous un de vos documents grâce à notre système d’échange gratuit de ressources numériques ou achetez-le pour la modique somme d’un euro symbolique. Cette aide totalement rédigée en format pdf sera utile aux lycéens ou étudiants ayant un devoir à réaliser ou une leçon à approfondir en : Echange
Compost.
I
INTRODUCTION
Compost, partially decomposed organic material used in gardening to improve soil and enhance plant growth. Compost improves the movement of water, dissolved
nutrients, and oxygen through the soil, making it easier for plant roots to absorb these vital substances.
A versatile material, compost benefits virtually any soil type. Clay soil, for example, has tiny, tightly packed particles that hamper the flow of water, nutrients, and
oxygen. Compost reconfigures the clay into larger, more loosely packed particles. The larger spaces between the particles improve the flow of water, oxygen, and
nutrients to roots. In addition, the roots are able to penetrate deeper into the soil and contact more nutrients. Compost also improves sandy soil, where the large
spaces between loosely packed particles enable water and its dissolved nutrients to drain too quickly for optimum root absorption. Compost soaks up and holds these
substances so that the roots have more time to absorb them. Compost also adds small amounts of zinc, copper, boron, and other vital nutrients to soils.
II
MAKING COMPOST
Compost is made by harnessing the natural decomposition process carried out by certain species of microorganisms. These microorganisms, primarily bacteria and
fungi, live in intimate association with their food supply--on the surface of dead plants, in soil, or on or in animal waste. By breaking down these materials with their
digestive enzymes, the tiny creatures release and absorb the nutrients within. For home gardeners, making compost is simply a matter of collecting food for
microorganisms in one place and letting them go to work.
A broad range of organic matter, including manure from plant-eating animals, grass clippings, and dead leaves or garden plants, provides a veritable feast for
microorganisms. For optimal decomposition, the combined starting materials should have an appropriate carbon to nitrogen ratio, preferably 30 parts carbon to 1 part
nitrogen. Leaves, straw, and paper, called brown materials, have a high carbon to nitrogen ratio, about 300 to 1, while grass clippings, kitchen scraps, and manure,
called green materials, have a low carbon to nitrogen ratio, about 15 to 1. For the best mix, green materials should be added in abundance; brown materials should be
used more sparingly. Materials that should not be used to make compost include manure from meat-eating animals, because it may contain disease-causing organisms
that can harm humans who eat plants grown in the compost. Meat should be avoided since it may attract rodents. Fatty foods such as cheese also should not be added
to the compost pile, as they are hard for most microorganisms to digest.
The starting materials are heaped into a pile--in a home garden, the pile is typically about a meter high and a meter wide (about three feet high and three feet wide);
on farms, composting is done on a larger scale. The pile may sit loose on the ground or it may be enclosed using a variety of materials, including wire fencing, wood
boards, cinder blocks, or widely stacked bricks.
III
MANAGING COMPOST
A variety of techniques may be used to increase the rate of compost decomposition. One technique is to cut the starting materials into 10- to 15-cm (4- to 6-in) pieces
to increase the surface area on which the microorganisms act. Increased surface area accelerates decomposition, much like a large ice chunk melts faster if broken up
into small pieces. The microorganisms in the compost pile also thrive when oxygen and moisture are present. Fluffing the compost pile every week or so with a pitchfork
or other tool introduces oxygen into the pile, and sprinkling water on the pile when it dries out provides the necessary moisture.
In a well-managed compost pile, the microorganisms eat and reproduce rapidly, and heat is released as a byproduct of their intense biochemical activity. The heat in the
pile kills most plant diseases and weed seeds that may have been present on the starting materials. The increased heat may also kill the microorganisms doing the
decomposing as well, especially those at the center of the pile where temperatures may climb to 90° C (200° F). Mixing the materials well about once a week prevents
lethal temperature increases by distributing the heat evenly throughout the pile.
The time it takes microorganisms to decompose the starting materials in compost varies. Factors include the size of the pile, the techniques used to manage the pile,
and the nature of the starting materials--green materials decompose readily, while brown materials take longer to break down. In an actively managed compost pile,
microorganisms use up their food supply and become less active after about six weeks. Then the pile slowly cools, signaling the near-final stages of decomposition. If
the materials in a compost pile are relatively large, if the pile is not kept moist, and if oxygen is not introduced, microorganism activity is slow and the pile does not heat
up. Depending upon the climate, it may take months or years for decomposition to occur.
No matter how long decomposition takes, when in its final stage, the compost pile is about half its original size and resembles dark soil. The material in the pile is now
called humus--although the terms humus and compost sometimes are used interchangeably. Humus is the highly beneficial material that is added to the garden soil.
Once in or on the soil, it continues to decompose at a very slow rate, releasing ammonia, carbon dioxide, and salts of calcium, phosphorus, and other elements that are
beneficial for plant growth.
Humus can be added to the soil at any time of year. It can be worked into the soil, where its benefits take effect most rapidly, or it can be left on the soil surface.
Humus can be used year after year, and there is never danger of adding too much, since this remarkable substance only enhances soil and encourages plants to thrive.
Cities compost on a large scale to reduce yard waste so that it does not take up space in landfills. Industries compost hazardous materials because the activities of the
microorganisms help break down toxic substances into less-harmful or harmless materials. Many municipalities provide information on composting as part of their
programs to reduce the amount of solid waste entering their landfills. County or regional offices of the state Cooperative Extension Service also have information on
composting.
Contributed By:
Erin Hynes
Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.
Compost.
I
INTRODUCTION
Compost, partially decomposed organic material used in gardening to improve soil and enhance plant growth. Compost improves the movement of water, dissolved
nutrients, and oxygen through the soil, making it easier for plant roots to absorb these vital substances.
A versatile material, compost benefits virtually any soil type. Clay soil, for example, has tiny, tightly packed particles that hamper the flow of water, nutrients, and
oxygen. Compost reconfigures the clay into larger, more loosely packed particles. The larger spaces between the particles improve the flow of water, oxygen, and
nutrients to roots. In addition, the roots are able to penetrate deeper into the soil and contact more nutrients. Compost also improves sandy soil, where the large
spaces between loosely packed particles enable water and its dissolved nutrients to drain too quickly for optimum root absorption. Compost soaks up and holds these
substances so that the roots have more time to absorb them. Compost also adds small amounts of zinc, copper, boron, and other vital nutrients to soils.
II
MAKING COMPOST
Compost is made by harnessing the natural decomposition process carried out by certain species of microorganisms. These microorganisms, primarily bacteria and
fungi, live in intimate association with their food supply--on the surface of dead plants, in soil, or on or in animal waste. By breaking down these materials with their
digestive enzymes, the tiny creatures release and absorb the nutrients within. For home gardeners, making compost is simply a matter of collecting food for
microorganisms in one place and letting them go to work.
A broad range of organic matter, including manure from plant-eating animals, grass clippings, and dead leaves or garden plants, provides a veritable feast for
microorganisms. For optimal decomposition, the combined starting materials should have an appropriate carbon to nitrogen ratio, preferably 30 parts carbon to 1 part
nitrogen. Leaves, straw, and paper, called brown materials, have a high carbon to nitrogen ratio, about 300 to 1, while grass clippings, kitchen scraps, and manure,
called green materials, have a low carbon to nitrogen ratio, about 15 to 1. For the best mix, green materials should be added in abundance; brown materials should be
used more sparingly. Materials that should not be used to make compost include manure from meat-eating animals, because it may contain disease-causing organisms
that can harm humans who eat plants grown in the compost. Meat should be avoided since it may attract rodents. Fatty foods such as cheese also should not be added
to the compost pile, as they are hard for most microorganisms to digest.
The starting materials are heaped into a pile--in a home garden, the pile is typically about a meter high and a meter wide (about three feet high and three feet wide);
on farms, composting is done on a larger scale. The pile may sit loose on the ground or it may be enclosed using a variety of materials, including wire fencing, wood
boards, cinder blocks, or widely stacked bricks.
III
MANAGING COMPOST
A variety of techniques may be used to increase the rate of compost decomposition. One technique is to cut the starting materials into 10- to 15-cm (4- to 6-in) pieces
to increase the surface area on which the microorganisms act. Increased surface area accelerates decomposition, much like a large ice chunk melts faster if broken up
into small pieces. The microorganisms in the compost pile also thrive when oxygen and moisture are present. Fluffing the compost pile every week or so with a pitchfork
or other tool introduces oxygen into the pile, and sprinkling water on the pile when it dries out provides the necessary moisture.
In a well-managed compost pile, the microorganisms eat and reproduce rapidly, and heat is released as a byproduct of their intense biochemical activity. The heat in the
pile kills most plant diseases and weed seeds that may have been present on the starting materials. The increased heat may also kill the microorganisms doing the
decomposing as well, especially those at the center of the pile where temperatures may climb to 90° C (200° F). Mixing the materials well about once a week prevents
lethal temperature increases by distributing the heat evenly throughout the pile.
The time it takes microorganisms to decompose the starting materials in compost varies. Factors include the size of the pile, the techniques used to manage the pile,
and the nature of the starting materials--green materials decompose readily, while brown materials take longer to break down. In an actively managed compost pile,
microorganisms use up their food supply and become less active after about six weeks. Then the pile slowly cools, signaling the near-final stages of decomposition. If
the materials in a compost pile are relatively large, if the pile is not kept moist, and if oxygen is not introduced, microorganism activity is slow and the pile does not heat
up. Depending upon the climate, it may take months or years for decomposition to occur.
No matter how long decomposition takes, when in its final stage, the compost pile is about half its original size and resembles dark soil. The material in the pile is now
called humus--although the terms humus and compost sometimes are used interchangeably. Humus is the highly beneficial material that is added to the garden soil.
Once in or on the soil, it continues to decompose at a very slow rate, releasing ammonia, carbon dioxide, and salts of calcium, phosphorus, and other elements that are
beneficial for plant growth.
Humus can be added to the soil at any time of year. It can be worked into the soil, where its benefits take effect most rapidly, or it can be left on the soil surface.
Humus can be used year after year, and there is never danger of adding too much, since this remarkable substance only enhances soil and encourages plants to thrive.
Cities compost on a large scale to reduce yard waste so that it does not take up space in landfills. Industries compost hazardous materials because the activities of the
microorganisms help break down toxic substances into less-harmful or harmless materials. Many municipalities provide information on composting as part of their
programs to reduce the amount of solid waste entering their landfills. County or regional offices of the state Cooperative Extension Service also have information on
composting.
Contributed By:
Erin Hynes
Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.
↓↓↓ APERÇU DU DOCUMENT ↓↓↓
