Plant Pedia: Organic Plant | Plant Biotechnology | Plant Science | Plant Tissue Culture
Showing posts with label Organic Plant. Show all posts
Showing posts with label Organic Plant. Show all posts

Friday, February 25, 2011

How to 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.

How to 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.

Decomposed Organic Material Used In Gardening


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.

Wednesday, February 2, 2011

Mycorrhiza as Biofertilizers


Mycorrhiza (fungus roots) is a distinct morphological structure which develops as a result of mutualistic symbiosis between some specific root - inhabiting fungi and plant roots. Plants which suffer from nutrient scarcity, especially P and N, develop mycorrhiza i.e. the plants belong to all groups e.g. herbs, shrubs, trees, aquatic, xerophytes, epiphytes, hydrophytes or terrestrial ones. In most of the cases plant seedling fails to grow if the soil does not contain inoculum of mycorrhizal fungi.

In recent years, use of artificially produced inoculum of mycorrhizal fungi has increased its significance due to its multifarous role in plant growth and yield, and resistance against climatic and edaphic stresses, pathogens and pests.

Mechanism of Symbiosis

The mechanism of symbiosis is not fully understood. Biorkman (1949) postulated the carbohydrate theory and explained the development of mycorrhizas in soils deficient in available P and N, and high light intensity. Slankis (1961) found that at high light intensity, surplus carbohydrates are formed which are exuded from roots. This in turn induces the mycorrhizal fungi of soil to infect the roots. At low light intensity, carbohydrates are not produced in surplus, therefore, plant roots fail to develop mycorrhizas.

Types of Mycorrhizas

By earlier mycologists the mycorrhizas were divided into the following three groups :

(i) Ectomycorrhiza. It is found among gymnosperms and angiosperms. In short roots of higher plants generally root hairs are absent. Therefore, the roots are infected by mycorrhizal fungi which, in turn, replace the root hairs (if present) and form a mantle. The hyphae grow intercellularly and develop Hartig net in cortex. Thus, a bridge is established between the soil and root through the mycelia.

(ii) Endomycorrhiza. The morphology of endomycorrhizal roots, after infection and establishment, remain unchanged. Root hairs develop in a normal way. The fungi are present on root surface individually. They also penetrate the cortical cells and get established intracellulary by secreting extracellular enzymes. Endomycorrhizas are found in all groups of plant kingdom.

(iii) Ectendomycorrhiza. In the roots of some of the gymnosperms and angiosperms, ectotrophic fungal infection occur. Hyphae are established intracellularly in cortical cells. Thus, symbiotic relation develops similar to ecto- and endo-mycorrhizas.

Marks (1991) classified the mycorrhizas into seven types on the basis of types of relationships with the hosts (i) vesicular-arbuscular (VA) mycorrhizas (coiled, intracellular hyphae, vesicle and arbuscules present), (ii) ectomycprrhizas (sheath and inter-cellular hyphae present), (iii) ectendomycorrhizas (sheath optional, inter and intra-cellular hyphae present), (iv) arbutoid mycorrhizas (seath, inter-and coiled intracellular hyphae present), (v) monotropoid mycorrhizas (sheath, inter- and intra- cellular hyphae and peg like haustoria present), (vi) ericoid mycorrhizas (only coiled intracellular hyphae, long coiled hyphae present), and (viii) orchidaceous mycorrhizas (only coiled intracellujlar hyphae present). Type (i) is present in all groups of plant kingdom; Types (ii) and (iii) are found in gymnosperms and angiosperms. Types (iv), (v) and (vi) are restricted to Ericales, Monotropaceae and Ericales respectively. Types (vii) is restricted to Orchidaceous only. Types (iv) and (v) were previously grouped under ericoid mycorrhizaes.

Methods of Inoculum Production and Inoculation

Methods of inoculum production of VAM fungi differ; however, some of these two are briefly described here.

(a) Ectomycorrhizal fungi: The basidiospores, chopped sporocarp, sclerotia, pure mycelia culture, fragmented mycorrhizal roots or soil from mycorrhizosphere region can be used as inoculum. The inoculum is mixed with nursery soils and seeds are sown.

Institute for Mycorrhizal Research and Development, U.S.A., Athens and Abbort Laboratories (U.S.A) have developed a mycelial inoculum of Pisolithus tinctorius in a vermiculite-peat moss substrate with a trade name ‘Myco-Rhiz’ which is now commercially available on large quantities. In 1982, about 1.5 million pine seedlings were produced with MycoRhiz in the U.S.A. (Marx and Schenck, 1983).

(b) VA mycorrhizal fungi : VA mycorrhizas can be produced on a large scale by pot culture technique. This requires the host plants, mycorrhizal fungi and natural soil. The host plants which support large scale production of inoculum are sudan grass, strawberry, sorghum, maize, onion, citrus, etc.

The starter inoculum (spores) of VA mycorrhizal fungi can be isolated from soil by wet sieving and decantation technique (Gerdeman and Nicolson, 1963). VA mycorrhizal spores are surface sterilized and brought to the pot culture. Commonly used pot substrates are sand: soil (1:1, w/w) with a little amount of moisture. An out line for inoculum production is given in Fig. 12.5.

There are two methods of using the inoculum : (i) using a dried spore-root- soil to plants by placing the inoculum several centimeters below the seeds or seedlings, (ii) using a mixture of soil-roots, and spores in soil pellets and spores adhered to seeds with adhesives.

Commercially available pot culture of VA mycorrhizal hosts grown under aseptic conditions can provide effective inoculum. Various types of VA mycorrhizal inocula are currently produced by Native Plants, Inc (NPI), Salt Lake City.

In India, Forest Research Institute, Dehra Dun has established mycorrhizal bank in different states of the country. Inocula of these can be procured as needed and used in horticulture and forestry programmes.

Benefits from Mycorrhizas to Plants

(i)

They increase the longevity of feeder roots, surface area of roots by forming mantle and spreading mycelia into soil and, in turn, the rate of absorption of major and minor nutrients from soil resulting in enhanced plant growth.

(ii)

They play a key role for selective absorption of immobile (P, Zn and Cu) and mobile (S, Ca, K, Fe, Mn, Cl, Br, and N) elements to plants. These are available to plants in less amount (Tinker, 1984).

(iii)

Some of the trees like pines cannot grow in new areas unless soil has mycorrhizal inocula because of limited or coarse root hairs.

(iv)

VA mycorrhizal fungi enhance water uptake in plants,

(v)

VA mycorrhizal fungi reduce plant response to soil stress such as high salt levels, toxicity associated with heavy metals, mine spoils, drought and minor element (e.g. Mn) imbalance.

(vi)

VA mycorrhizal fungi decrease transplant socks to seedlings. They produce organic 'glues' which bind soil particles into semistable in aggregates. Thus, they play a significant role in augmenting soil fertility and plant nutrition.

(vii)

Some of them produce metabolites which change the ability of plants to induce roots from woody plant cuttings and increase root development during vegetative propagation.

(viii)

They increase resistance in plants and with their presence reduce the effects of pathogens and pests on plant health.



Saturday, July 24, 2010

Biofertilizers


The use of biofertilizers, biological systems that supply plant nutrients such as nitrogen to agricultural crops, could reduce agriculture’s dependency on chemical fertilizers, which are often detrimental to the environment.

Plants require an adequate supply of the thirteen mineral nutrients necessary for normal growth
and reproduction. These nutrients, which must besupplied by the soil, include both macronutrients (nutrients required in large quantities) and micronutrients (nutrients required in smaller quantities).

As plants grow and develop, they remove these essential mineral nutrients from the soil. Because normal crop production usually requires the removal of plants or plant parts, the nutrients are continuously removed from the soil. Therefore, the long-term agricultural utilization of any soil requires periodic fertilization to replace lost nutrients.

Nitrogen is the plant nutrient that is most often depleted in agricultural soils, and most crops respond to the addition of nitrogen fertilizer by increasing their growth and yield. Therefore, more nitrogen is applied to cropland than any other fertilizer component. In the past, nitrogen fertilizers have been limited to either manures, which have low levels of nitrogen, or chemical fertilizers, which usually have high levels of nitrogen. However, the excess nitrogen in chemical fertilizers often runs off into nearby waterways, causing a variety of environmental problems.

Less Harmful Alternatives

Biofertilizers offer a potential alternative: They supply sufficient amounts of nitrogen for maximum yields yet have a positive impact on the environment. Biofertilizers generally consist of either naturally occurring or genetically modified microorganisms that improve the physical condition of soil, aid plant growth, or increase crop yield. Biofertilizers provide an environmentally friendly way to increase plant health and yields with reduced input costs,newproducts and additional revenues for the agricultural biotechnology industry, and cheaper products for consumers.

Nitrogen Fixing

While biofertilizers could potentially be used to supply a number of different nutrients, most of the interest is focused on nitrogen. The relatively small amounts of nitrogen found in soil come froma variety of sources. Some nitrogen is present in all organic matter in soil; as this organic matter is degraded by microorganisms, it can be used by plants. A second source of nitrogen is nitrogen fixation, the chemical or biological process of taking nitrogen from the atmosphere and converting it to a form that can be used by plants. Bacteria such as members of Rhizobium can live symbiotically in the roots of certain plants, such as legumes.

Rhizobia

and plant root tissue form root nodules, which house the nitrogen-fixing bacteria; once inside the
nodules, the bacteria use energy supplied by the plant to convert atmospheric nitrogen to ammonia, which nourishes the plant. Natural nitrogen can also be supplied by free-living microorganisms, which can fix nitrogen without forming a symbiotic relationship with plants. The primary objective of biofertilizers is to enhance any one or all of these processes.

One of the major goals for the genetic engineering of biofertilizers is to transfer the ability to formnodules and establish effective symbiosis to nonlegume plants. The formation of nodules in whichthe Rhizobia live requires plant cells to synthesize many new proteins, and many of the genes required for the expression of these proteins are not found in the root cells of plants outside the legume family (Fabaceae). If transfer of the appropriate genes could be accomplished, Rhizobia could be used as a biofertilizer for a variety of plants.

There is also much interest in using the freeliving, soil-borne organisms that fix atmospheric
nitrogen as biofertilizers. These organisms, including types bacteria and algae, live in the rhizosphere (the region of soil in immediate contact with plant roots) or thrive on the surface of the soil. Because the exudates from these microorganisms contain nitrogen that can be used by plants, increasing their abundance in the soil could reduce the dependency on chemical fertilizers. Numerous research efforts have been designed to identify and enhance the
abundance of nitrogen-fixing bacteria in the rhizosphere.

Soil microorganisms primarily depend on soluble root exudates and decomposed organic
matter to supply the energy necessary for fixing nitrogen. Hence, there is also an interest in enhancing the biodegradation of organic matter in the soil. This research has primarily centered on inoculating the soil with cellulose-degrading fungi and nitrogenfixing bacteria or applying organic matter, such as straw that has been treated with a combination of the fungi and bacteria to the soil.

Thursday, July 1, 2010

'Balanced' Ecosystems Seen in Organic Agriculture Better at Controlling Pests, Research Finds

There really is a balance of nature, but as accepted as that thought is, it has rarely been studied. Now Washington State University researchers writing in the journal Nature have found that more balanced animal and plant communities typical of organic farms work better at fighting pests and growing a better plant.

The researchers looked at insect pests and their natural enemies in potatoes and found organic crops had more balanced insect populations in which no one species of insect has a chance to dominate. And in test plots, the crops with the more balanced insect populations grew better.

"I think 'balance' is a good term," says David Crowder, a post-doctorate research associate in entomology at Washington State University. "When the species are balanced, at least in our experiments, they're able to fulfill their roles in a more harmonious fashion."

Crowder and colleagues here and at the University of Georgia use the term "evenness" to describe the relatively equal abundance of different species in an ecosystem. Conservation efforts more typically concentrate on species richness -- the number of individual species -- or the loss of individual species. Crowder's paper is one of only a few to address the issue. It is the first the first to look at animal and fungal communities and at multiple points in the food chain.

The researchers say their results strengthen the argument that both richness and evenness need to be considered in restoring an ecosystem. The paper also highlights insect predator and prey relationships at a time when the potato industry and large French fry customers like McDonald's and Wendy's are being pushed to consider the ecological sustainability of different pest-control practices.

Conventional pest-management on farms often leads to biological communities dominated by a few species. Looking at conventional and organic potato farms in central Washington State's Columbia Basin, Crowder found that the evenness of natural pests differed drastically between the two types of farms. In the conventional fields, one species might account for four out of five insects. In the organic fields, the most abundant species accounted for as little as 38 percent of a field's insect predators and enemies.

Using field enclosures on Washington State University's Pullman campus, Crowder recreated those conditions using potato plants, Colorado potato beetles, four insect species and three soil pathogens that attack the beetles. When the predators and pathogens had similar numbers, says Crowder, "we would get significantly less potato beetles at the end of the experiment."

"In turn," he adds, "we'd get bigger plants."

Crowder says he is unsure why species evenness was lower in conventional crops. It could be from different types of fertilization or from insecticides killing some natural enemies more than others.