A cover crop is a plant grown primarily to manage soil erosion, soil fertility, soil quality, water, weeds, pests, diseases, biodiversity and wildlife within agroecosystem et al. 2000), ecological systems are managed and largely shaped by humans in varying intensities to produce food, feed, or fiber. Currently, not many countries are known to use the cover crop method.
Crop cover is of interest in sustainable agriculture as many of them enhance the sustainability of agro-ecosystem attributes and may also indirectly improve the quality of the surrounding natural ecosystems. Farmers choose to plant and manage specific types of crops based on their own needs and objectives, influenced by the biological, environmental, social, cultural, and economic factors of the food systems in which they operate (Snapp et al., 2005). Agronomic studies are beginning to pay attention to cost/benefit analysis and certain growth methods, to address the practical concerns of farmers. The practice of farm cover crops has been recognized as climate smart agriculture by the White House.
Video Cover crop
Erosi tanah
Although cover crops can perform multiple functions in agroecosystems simultaneously, these plants are often grown for the sole purpose of preventing soil erosion. Soil erosion is a process that can irreversibly reduce the agro-ecosystem's productive capacity. Dense crops stand physically slow down rainfall speed before surface contact, preventing soil splashing and erosion surface runoff (Romkens et al., 1990). In addition, extensive root crop roots help anchor the soil in place and increase soil porosity, creating a suitable habitat network for soil macrofauna (Tomlin et al., 1995). It makes good soil enrichment for the next few years.
Maps Cover crop
Soil fertility management
One of the main uses of cover crops is to improve soil fertility. This type of cover crop is referred to as "green manure." They are used to manage various soil macronutrients and micronutrients. Of the various nutrients, the crop-covering effect on nitrogen management has received the greatest attention from researchers and farmers, as nitrogen often becomes the most restrictive nutrient in crop production.
Often, green manure crops are planted for a certain period, and then plowed down before reaching full maturity to improve soil fertility and quality. Also the remaining trunks block the soil so as not to erode.
Green manure plants are generally leguminous in color, which means they are part of the Fabaceae family (nuts). This family is unique because all the species in it organize pods, such as nuts, lentils, lupins and alfalfa. Soil cover crops contain high nitrogen and can often provide the amount of nitrogen needed for crop production. In conventional farming, this nitrogen is usually applied in the form of chemical fertilizers. The quality of this cover crop is called the fertilizer replacement value (Thiessen-Martens et al., 2005).
Another unique quality for leguminous crops is that they form a symbiotic relationship with rhizobial bacteria located in the legume root nodula. Lupine is nodulated by soil microorganisms Bradyrhizobium sp. (Lupine). Bradyrhizobia is encountered as a microscion in other legume plants ( Argyrolobium , Lotus , Ornithopus , Acacia , Lupine ) of Mediterranean origin. These bacteria convert atmospheric nitrogen gas that is not available biologically ( N
2 ) for biologically available ammonium (
4 ) through biological nitrogen fixation process.
Prior to the advent of the Haber-Bosch process, an energy-intensive method developed to conduct industrial nitrogen fixation and make chemical nitrogen fertilizers, most of the nitrogen introduced to the ecosystem emerges through biological nitrogen fixation (Galloway et al., 1995). Some scientists believe that widespread biological nitrogen fixation, achieved primarily through the use of cover crops, is the only alternative to industrial nitrogen fixation in order to maintain or improve future levels of food production (Bohlool et al 1992, Peoples and Craswell 1992, Giller and Cadisch 1995). Industrial nitrogen fixation has been criticized as an unsustainable nitrogen source for food production due to its dependence on fossil fuel energy and the environmental impact associated with the use of chemical nitrogen fertilizers in agriculture (Jensen and Hauggaard-Nielsen 2003). Large environmental impacts such as loss of nitrogen fertilizer to waterways, which can lead to eutrophication (subsequent nutrient loading) and subsequent hypoxia (oxygen depletion) from large bodies of water.
An example of this is in the Valley of the Mississippi Valley, where years of loading nitrogen fertilizers into the watersheds of agricultural production have produced hypoxic "dead zones" in the New Jersey-size Gulf of Mexico (Rabalais et al., 2002). The ecological complexity of marine life in this zone has decreased as a consequence (CENR 2000).
As well as bringing nitrogen to the agroecosystem through biological nitrogen fixation, this type of cover crop known as "capture plant" is used to retain and recycle the nitrogen of the existing soil. The capture plants take the remaining nitrogen surplus from previous plant fertilization, preventing it lost through leaching (Morgan et al. 1942), or gas denitrification or volatilization (Thorup-Kristensen et al., 2003).
Catch a plant is usually a fast growing annual cereal type adapted to scavenge nitrogen available efficiently from the ground (Ditsch and Alley 1991). The nitrogen bonded in capture biomass crops is released back to the soil after the catching crop is entered as a green manure or otherwise begins to decompose.
An example of the use of green manures comes from Nigeria, where cover crops Mucuna pruriens (peanut velvet) have been found to increase the availability of phosphorus in the soil after a farmer applies phosphate rock (Vanlauwe et al. 2000).
Soil quality management
Crop cover can also improve soil quality by increasing the level of soil organic matter through plant cover biomass input over time. Increased soil organic matter improves soil structure, as well as water and nutrient holding capacity and soil buffer capacity (Patrick et al., 1957). This can also lead to an increase in soil carbon uptake, which has been promoted as a strategy to help offset rising levels of atmospheric carbon dioxide (Kuo et al. 1997, Sainju et al., 2002, Lal 2003).
Soil quality is managed to produce optimal state for plants to grow. The main factors of soil quality are soil salinity, pH, microorganism balance and prevention of soil contamination.
Water management
By reducing soil erosion, cover crops also often reduce the rate and quantity of water that flows off the land, which would normally cause environmental risks to downstream waterways and ecosystems (Dabney et al., 2001). The plant biomass cover acts as a physical barrier between rainfall and ground level, allowing raindrops to continue to flow through the soil profile. Also, as stated above, the growth of cover crops masks results in the formation of soil pores, which in addition to enhancing the macrofauna habitat of the soil provide a waterway for filtering through soil profiles rather than flowing from the field as surface runoff. With an increase in water infiltration, the potential for groundwater storage and aquifer fill can be increased (Joyce et al., 2002).
Just before the cover crop is killed (by such practices including cutting, processing, discing, rolling, or herbicide application) they contain a large amount of moisture. When the cover crop is put into the soil, or left on the soil surface, it often increases soil moisture. In agroecosystems where water for crop production is less available, cover crops can be used as mulch to conserve water with shade and cool the soil surface. This reduces moisture evaporation of the soil. In other situations, farmers try to dry the soil as soon as possible into the growing season. Here prolonged soil moisture conservation can be a problem.
While cover crops can help to conserve water, in temperate climates (especially in years with below average rainfall) they can attract groundwater supplies in the spring, especially if good climatic growth conditions. In this case, shortly before planting, farmers often face a tradeoff between the benefits of increased cover crop growth and reduced soil moisture loss for cash crop production during the season. The C/N ratio is balanced with this application.
Weed management
Thick plant cover plants often compete well with weeds during periods of plant growth cover, and can prevent most of the seed weed germinates to complete the cycle of life and reproduce. If the cover crop is left on the soil surface rather than put into the soil as a green manure after its growth is stopped, it can form an almost impenetrable mat. This drastically reduces the transmission of light to weed seeds, which in many cases reduces the seed weed germination rate (Teasdale 1993). Furthermore, even when weed seeds germinate, they often run out of stored energy for growth before building the structural capacity necessary to penetrate the mulch layer of the cover crop. This is often referred to as the cover effect of plant cover crops (Kobayashi et al., 2003).
Some cover crops suppress weeds both during growth and after death (Blackshaw et al., 2001). During this growth the cover crops vigorously compete with weeds for space, light, and nutrients available, and after death they withhold the next strain by forming a layer of mulch at the soil surface. For example, Blackshaw et al. (2001) found that when using Melilotus officinalis (yellow sweet potato) as a cover crop in an improved fallow system (where the fallow period is intentionally enhanced by a number of different management practices, including planting of plant cover) weed biomass represents only between 1-12% of the total standing biomass at the end of the plant growth season. Furthermore, after closing the cover crop, the yellow sweetclover residue suppresses the weeds to a level 75-97% lower than the fallow (no yellow sweetclover) system.
In addition to competition or physical competition-based weeds, certain cover crops are known to suppress weeds through allelopathy (Creamer et al. 1996, Singh et al., 2003). This occurs when certain biochemical cover crop compounds are degraded which are accidentally toxic, or inhibit seed germination, other plant species. Some of the most notable examples of allelopathic cover plants are Secale cereale (rye), Vicia villosa (vack hairy), Trifolium pratense (red clover) < Sorgum bicolor (sorghum-sudangrass), and species in the Brassicaceae family, especially mustard (Haramoto and Gallandt 2004). In one study, residual rye cover crops were found to have provided between 80% and 95% of early season wide leaf weed control when used as mulch during different crop production such as soybeans, tobacco, maize, and sunflower (Nagabhushana et al., 2001).
In a recent study released by Agricultural Research Service (ARS) researchers examined how the rate of rye seeding and planting patterns affect the production of cover crops. [1] The results show that growing more pounds per hectare of wheat increases the production of plant cover and decreases the number of weeds. The same thing happens when scientists test seeding levels on beans and wheat; the higher seed density grown per acre decreases the number of weeds and increases the yield of legumes and oats. The planting pattern, which consists of traditional lines or grid patterns, does not appear to have a significant impact on crop production or on weed production in cover crops. The ARS scientists concluded that increasing the seeding rate could be an effective weed control method.
Disease management
In the same way that allelopathic properties of cover crops can suppress weeds, they can also break disease cycles and reduce populations of bacterial and fungal diseases (Everts 2002), and parasitic nematodes (Potter et al. 1998, Vargas-Ayala et al. 2000). Species within the Brassicaceae family, such as mustard greens, have been widely shown to suppress populations of fungal diseases through the release of naturally occurring toxic chemicals during the degradation of glucosinolade compounds in their plant cellular tissues (Lazzeri and Manici 2001).
Pest management
Some cover crops are used as so-called "trap crops", to attract pests from crops and to what is considered pests as better habitat (Shelton and Badenes-Perez 2006). Plant trap areas can be established inside the plant, inside the farm, or in the landscape. In many cases, plant traps are planted during the same season as food crops are produced. The limited area occupied by these trapping plants can be treated with pesticides when the pest is attracted to a trap large enough to reduce pest populations. In some organic systems, farmers control trap crops with large vacuum-based tools to physically pull pests out of plants and out of the field (Kuepper and Thomas 2002). This system has been recommended to be used to help control the lygus bug in the production of organic strawberries (Zalom et al., 2001). Other examples of trap crops are the white mustard resistance nematodes ( Sinapis alba ) and radishes ( Raphanus sativus ). They can grow after the main crop (cereal) and capture the nematodes, such as the bit cyst nematodes and the nematodes of Columbus root nodes. As it grows, nematodes hatch and are attracted to the roots. After entering the roots they can not reproduce at the root due to the hypersensitive resistance reaction of the plant. Therefore the nematode population is greatly reduced, by 70-99%, depending on species and cultivation time.
Other cover crops are used to attract natural pest predators by providing their habitat elements. This is a form of biological control known as habitat augmentation, but is achieved by the use of cover crops (Bugg and Waddington 1994). Findings on the relationship between the presence of cover crops and the predator/pest population dynamics have been mixed, pointing towards the need for detailed information on certain types of cover crops and management practices to complement the integrated pest management strategy provided. For example, the predatory mite Euseius tularensis (Congdon) is known to help control thrus thrus pests in the Central California citrus orchard. The researchers found that the planting of several different legume cover crops (such as beans, vetch wollypod, New Zealand white clover, and Austrian winter nuts) provided sufficient pollen as a food source to cause seasonal increases in E. tularensis population, which at the right time can potentially introduce sufficient predatory pressure to reduce the population of citrus thrips (Grafton-Cardwell et al., 1999).
Diversity and wildlife
Although cover crops are usually used to serve one of the purposes discussed above, they often simultaneously increase agricultural habitat for wildlife. The use of cover crops adds at least another dimension of plant diversity to the rotation of commercial crops. Since cover crops are not usually valuable crops, their management is usually less intensive, providing a "soft" window of human influence on agriculture. This relatively "hands-off" management, combined with increased heterogeneity in agriculture created by the formation of cover crops, increases the likelihood that more complex trophic structures will evolve to support higher levels of wildlife diversity (Freemark and Kirk 2001).
Source of the article : Wikipedia
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