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A beneficial weed can be an invasive plant that has some companion plant effect which is edible, contributes to soil health, adds ornamental value, [1] [2] and as well as beneficial also. These plants are normally not domesticated. However, some invasive plants, such as dandelions are commercially cultivated in addition to growing in the wild. Beneficial weeds include many wildflowers, as well as other weeds that are commonly removed or poisoned. [3] Certain weeds that have obnoxious and destructive qualities have been shown to fight illness and are thus used in medicine. Reductions in abundances of weeds which act as hosts may affect associated insects and other taxa which are beneficial. For example, Parthenium hysterophorus which is native to Northern Mexico and parts of the US, has been an issue for years due to its toxicity and ability to spread rapidly. In the past few decades though research has found that Parthenium hysterophorus has been used in traditional medicine to treat inflammation, pain, fever, neurological disorders and diseases like malaria dysentery. [4] It is also known to create Biogas that can be used as a bioremediation agent to break down heavy metals and other pollutants. [5]
Beneficial weeds are erroneously considered to compete with neighboring plants for food and moisture. However, some "weeds" provide the soil with nutrients, either directly or indirectly.
Many weeds protect nearby plants from pest insects. Some beneficial weeds release volatile organic compounds that mask the scents of nearby plants, as with alliums and wormwood; others imitate the pheromones of pest insects and confuse them, as with ground ivy, oregano, and other mints. In addition, a number of beneficial weeds have spines or other features that deter pest insects.
Some weeds act as trap crops, distracting pests away from valued plants. Insects often search for target plants by smell, and then land at random on anything green in the area of the scent. If they land on an edible "weed", they will stay there instead of going on to the intended victim. Sometimes, they actively prefer the trap crop.
The use of certain weeds integrated around native or otherwise intended plants has been found to be beneficial in many ways. A 2015 study showed that the presence of other plants or decoy plants made of green plastic, cardboard, or any other green materials can significantly reduce the success rate of flying pests in locating their host plants. [10] These pests:
Some "weed" species, such as subterranean clover ( Trifolium subterraneum L .), have been found to be specifically beneficial against pests targeting crops of common cabbage ( Brassica) species, reducing insects by 39%-100% on brassica plants when they were sown surrounded with clover as compared to when surrounded by bare soil. [14] The differences in the colonization of such insects appear sufficient to determine the lower numbers of insects found that where when host plants are surrounded and under sown with clover.
Many plants can grow intercropped in the same space because they exist on different levels in the same area, providing ground cover or working as a trellis for each other. [15] This healthier style of horticulture is called forest gardening. Larger plants provide a wind break or shelter from the noonday sun for more delicate plants.
Conversely, some intercropped plants provide a living mulch effect, able to inhibit the growth of harmful weeds and create a humid, cooler microclimate around nearby plants to stabilize soil moisture.
Plants such as ryegrass, red clover, and white clover are examples of "weeds" that are living mulches, often welcomed in horticulture.
Plants or fungi can be repelled through a chemical means known as allelopathy. [16] Certain plants can be affected by a chemical emission through their roots or air, slowing their growth, preventing seed germination, or even killing them.
A common companion plant benefit from many weeds is to attract and provide habitat for beneficial insects or other organisms that benefit plants.
For example, wild umbellifers attract predatory wasps and flies. The adults eat nectar, but they feed common garden pests to their offspring. [17]
Some weeds attract lady beetles or "good" types of nematodes, or provide ground cover for predatory beetles.
Crop rotation is the practice of growing a series of different types of crops in the same area across a sequence of growing seasons. This practice reduces the reliance of crops on one set of nutrients, pest and weed pressure, along with the probability of developing resistant pests and weeds.
Companion planting in gardening and agriculture is the planting of different crops in proximity for any of a number of different reasons, including weed suppression, pest control, pollination, providing habitat for beneficial insects, maximizing use of space, and to otherwise increase crop productivity. Companion planting is a form of polyculture.
Weed control is a type of pest control, which attempts to stop or reduce growth of weeds, especially noxious weeds, with the aim of reducing their competition with desired flora and fauna including domesticated plants and livestock, and in natural settings preventing non native species competing with native species.
Intercropping is a multiple cropping practice that involves the cultivation of two or more crops simultaneously on the same field, a form of polyculture. The most common goal of intercropping is to produce a greater yield on a given piece of land by making use of resources or ecological processes that would otherwise not be utilized by a single crop.
In agriculture, a green manure is a crop specifically cultivated to be incorporated into the soil while still green. Typically, the green manure's biomass is incorporated with a plow or disk, as is often done with (brown) manure. The primary goal is to add organic matter to the soil for its benefits. Green manuring is often used with legume crops to add nitrogen to the soil for following crops, especially in organic farming, but is also used in conventional farming.
In agriculture, cover crops are plants that are planted to cover the soil rather than for the purpose of being harvested. Cover crops manage soil erosion, soil fertility, soil quality, water, weeds, pests, diseases, biodiversity and wildlife in an agroecosystem—an ecological system managed and shaped by humans. Cover crops can increase microbial activity in the soil, which has a positive effect on nitrogen availability, nitrogen uptake in target crops, and crop yields. Cover crops reduce water pollution risks and remove CO2 from the atmosphere .Cover crops may be an off-season crop planted after harvesting the cash crop. Cover crops are nurse crops in that they increase the survival of the main crop being harvested, and are often grown over the winter. In the United States, cover cropping may cost as much as $35 per acre.
A mulch is a layer of material applied to the surface of soil. Reasons for applying mulch include conservation of soil moisture, improving fertility and health of the soil, reducing weed growth, and enhancing the visual appeal of the area.
In agriculture, polyculture is the practice of growing more than one crop species together in the same place at the same time, in contrast to monoculture, which had become the dominant approach in developed countries by 1950. Traditional examples include the intercropping of the Three Sisters, namely maize, beans, and squashes, by indigenous peoples of Central and North America, the rice-fish systems of Asia, and the complex mixed cropping systems of Nigeria.
In agriculture, a living mulch is a cover crop interplanted or undersown with a main crop, and intended to serve the purposes of a mulch, such as weed suppression and regulation of soil temperature. Living mulches grow for a long time with the main crops, whereas cover crops are incorporated into the soil or killed with herbicides.
Worldwide more human beings gain their livelihood from agriculture than any other endeavor; the majority are self-employed subsistence farmers living in the tropics. While growing food for local consumption is the core of tropical agriculture, cash crops are also included in the definition.
This is an alphabetical index of articles related to gardening.
The carrot fly is a pest of gardens and farms, and mainly affects the crop of carrots, but can also attack parsnips, parsley and celery. It is a member of the family Psilidae.
Delia flies are members of the Anthomyiidae family within the superfamily Muscoidae. The identification of different species of Delia can be very difficult for non-specialists as the diagnostic characteristics used for immature and/or female specimens may be inconsistent between species. Past taxonomic keys were not as comprehensive in their identification of Delia specimens; they were either too reliant on genetic characteristics, focused solely on a specific life stage, or were focused only on certain species. However current taxonomic keys aim to be more thorough by not only including morphological diagnostics for males, females, and immature specimens of various species, but also their genetic make-up or molecular barcode.
A trap crop is a plant that attracts agricultural pests, usually insects, away from nearby target crops. This form of companion planting can save a target crop from decimation by pests without the use of artificial pesticides. A trap crop is used for attracting the insect and pests away from a target crop field. Many trap crops have successfully diverted pests from focal crops in small scale greenhouse, garden and field experiments; a small portion of these plants have been shown to reduce pest damage at larger commercial scales. A common explanation for reported trap cropping failures, is that attractive trap plants only protect nearby plants if the insects do not move back into the target crop. In a review of 100 trap cropping examples in 2006, only 10 trap crops were classified as successful at a commercial scale, and in all successful cases, trap cropping was supplemented with management practices that specifically limited insect dispersal from the trap crop back into the target crop.
A weed is a plant considered undesirable in a particular situation, growing where it conflicts with human preferences, needs, or goals. Plants with characteristics that make them hazardous, aesthetically unappealing, difficult to control in managed environments, or otherwise unwanted in farm land, orchards, gardens, lawns, parks, recreational spaces, residential and industrial areas, may all be considered weeds. The concept of weeds is particularly significant in agriculture, where the presence of weeds in fields used to grow crops may cause major losses in yields. Invasive species, plants introduced to an environment where their presence negatively impacts the overall functioning and biodiversity of the ecosystem, may also sometimes be considered weeds.
Parthenium hysterophorus is a species of flowering plant in the family Asteraceae. It is native to the American tropics. Common names include Santa-Maria, Santa Maria feverfew, whitetop weed, and famine weed. In India, it is locally known as carrot grass, congress grass or gajar ghas or dhanura. It is a common invasive species in India, Australia, and parts of Africa.
Mechanical weed control is a physical activity that inhibits unwanted plant growth. Mechanical, or manual, weed control techniques manage weed populations through physical methods that remove, injure, kill, or make the growing conditions unfavorable. Some of these methods cause direct damage to the weeds through complete removal or causing a lethal injury. Other techniques may alter the growing environment by eliminating light, increasing the temperature of the soil, or depriving the plant of carbon dioxide or oxygen. Mechanical control techniques can be either selective or non-selective. A selective method has very little impact on non-target plants where as a non-selective method affects the entire area that is being treated. If mechanical control methods are applied at the optimal time and intensity, some weed species may be controlled or even eradicated.
Altica cyanea is a species of flea beetle. It is a pest of millets such as sorghum in India. It is being investigated as a biological pest control of Ludwigia adscendens, a common weed in rice fields.
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