Joel Gruver, Western Illinois University. Dr. Weil, University of Maryland. Charles White, Penn State University. What is the Conservation Reserve Program (CRP)? The Conservation Reserve Program (CRP) is a land conservation program administered by the Farm Service Agency (FSA). Dr. Yvonne Lawley, University of Manitoba. Over the past decade, radishes have been redefined; once known almost exclusively as a pungent vegetable, radishes have recently gained recognition for their cover cropping potential. After reading this article, you'll be able to make an informed decision about whether cover crop radishes are worth a try on your farm. Radishes have made rapid inroads as a cover crop for several reasons. First, the radish phenotype is well suited to perform many valuable cover crop functions. August 3, 2012 Issue: A weekly summary of world developments in agri-biotech for developing countries, produced by the Global Knowledge Center on Crop Biotechnology. The content on this page is available as a topic brief (PDF download), Cover Crops for Sustainable Crop Rotations. Use the green Order button on this page to order. Infants and Toddlers: The mouths of babes Leslie Alexander Restoration Herbs. Leslie Alexander begins by talking about stages of development in utero and. Staff from Under Armour and students from two local schools set oyster cages at a local dock. Maryland Oyster Gardening Program. From the Field: Sustainable Agriculture in Lancaster County, Pennsylvania from Chesapeake Bay Program on Vimeo. Conservation tillage leaves one. Joanne Whalen, Extension IPM Specialist; [email protected]. As you make plans to plant wheat, you should consider the following factors when making a treatment. Second, recent research including many on- farm trials has documented beneficial effects of radish cover crops on soil properties and subsequent crops. Third, the seed industry has ramped up production of radish seed, brought new branded products to market, and promoted radish as a cover crop. Between 1. 0/1/2. Crop Talk forum of New Ag Talk, with over 5. Radish Seedstock. Most of the radish varieties currently marketed for cover cropping (e. Ground. Hog radish. All are morphologically similar to the large white daikon radishes traditionally used in Asian cooking. Hybrid daikon- type culinary radish seed is prohibitively expensive (more than $1. Standard oilseed radish cultivars (e. Adagio, Colonel, and Defender) tend to have a stubbier, more branched taproot, greater winter hardiness, and lower seed cost than larger- rooted daikon types (Ngouajio and Mutch, 2. There are currently 2 radish varieties marketed for cover cropping with certified genetics - Graza and Tillage Radish. Graza from Pyne Gould Guinness Seeds (PGG, Ltd.) in New Zealand was developed over 1. The breeding program selected for smooth leaves, ability to recover from multiple grazings, and resistance to bolting. Graza will grow vegetatively for an extended period when spring planted unlike most other cover crop radishes. Compared to rape and forage turnips, Graza radishes have greater ability to respond to high fertility and build up larger root reserves, providing more resilience under difficult conditions (Stewart and Moorhead, 2. Plant Variety Protection status in June 2. Unauthorized propagation of Graza and Tillage Radish. Plant Variety Protection pending statute, and unauthorized propagation is strictly prohibited. Plant Variety Protection, indicating that it is a unique variety. Tillage Radish. Plant Variety Protection pending statute, and unauthorized propagation is strictly prohibited. Plant Variety Protection pending statute, and unauthorized propagation is strictly prohibited. Plant Variety Protection pending statute, and unauthorized propagation is strictly prohibited. In recent years, some farmers who purchased inexpensive radish seed have reported high levels of variability including early bolting. In response to the growing interest in radishes for cover cropping, some public and private breeding programs are starting to select for radishes with superior cover crop attributes. More research is needed comparing radish varieties with respect to traits such as winter- hardiness, hard- seededness, seedling vigor, nutrient scavenging, root penetration strength, and biofumigation potential. The information that follows should be generally applicable to all radish cultivars used for cover cropping unless otherwise noted. In addition, literature discussing other cool season annual brassica cover crops (e. Benefits of Radish Cover Crops. Effects on Soil Structure. The radish attribute that has captured the most farmer interest is their robust rooting ability. Under favorable growing conditions, radish roots can extend more than 3 feet deep in 6. Plants with roots more than 1 inch in diameter normally have a significant portion of the root exposed above ground (often more than 4 inches, even in uncompacted soils) (Fig. Typical above ground growth of the storage root after 6. Photo credit: Joel Gruver, Western Illinois University. After radishes winter- kill and their large fleshy roots desiccate, the channels created by the roots tend to remain open at the soil surface, improving infiltration, surface drainage, and soil warming (Fig. Radish rooting effects on soil porosity also extend into the subsoil. This general process called bio- drilling, can improve root growth by subsequent crops and access to subsoil moisture resulting in greater resilience under drought conditions (Chen and Weil, 2. Figure 2. Radish holes after winterkill. Photo credit: Joel Gruver, Western Illinois University. Research at the University of Maryland has shown that radish roots have greater ability to penetrate compacted soil than cereal rye and rapeseed (Chen and Weil, 2. Subsequent research found twice as many corn roots penetrated compacted subsoil after radish cover cropping as compared to cereal rye, with both cover crops promoting more rooting than bare- fallow (Fig. These results suggest that radishes may be useful as a biological alternative to deep ripping and other mechanical methods of alleviating soil compaction. Some farmers and researchers are currently evaluating bio- strip- till strategies which involve targeted fall planting of radishes on the wide rows (e. This approach reduces seed cost and may maximize crop utilization of radish root channels but requires precise equipment guidance in the field. More information about bio- strip- till planting methods is contained in the section on seeding. Figure 3. Enhanced corn and soybean root density following radish as compared to rye and no cover. Figure credit: Guihua Chen, University of Maryland. Effects on Weeds. A good stand of radishes can eliminate nearly all weed growth both during and for some time after active radish growth (Fig. To obtain near- complete weed suppression, radishes should be planted early (6 or more weeks before frost), at a relatively high population (more than 5 plants per square foot) into a clean seed bed. Weed suppression from fall planted radishes typically lasts into April, but does not extend much into the summer cropping season. Figure 4. Near- complete suppression of weeds in April (Hayden Farm, Beltsville, MD). Photo credit: Yvonne Lawley, University of Manitoba. Recent research at the University of Maryland investigated the mechanisms through which radishes provide weed suppression. Over ten site- years, they found that radishes provided complete suppression of winter annual weeds in the fall and early spring but the suppression did not persist into the summer crop. Controlled environment bioassays involving cover crop amended soil, aqueous plant extracts, and aqueous soil extracts along with a field experiment involving planted weed seeds did NOT provide evidence of allelopathy. In a residue moving experiment, no differences in spring weed suppression were observed if radish residues were removed prior to a killing frost in November or left in place to decompose (3 out of 4 site- years). These results were supported by planting date experiments where fall ground cover and spring weed suppression was greatest for the earliest radish planting dates. The University of Maryland researchers concluded that rapid and competitive fall growth, rather than allelopathy, is the primary mechanism of weed suppression by radishes (Lawley et al., 2. Effects on Seed Bed Preparation. After winter- kill (or other causes of mortality), radish residues deteriorate rapidly. As a result, fall biomass production is unlikely to interfere with spring field work. Typically a good stand of winter- killed radishes leaves the soil surface weed free and perforated with open root holes in early spring. As a result, the soil warms up and dries out faster than soils covered by either winter weeds or a growing cover crop and is conducive to earlier spring planting (Fig. Warmer and drier seedbed in April with forage radish compared to rye as cover crop. Figure credit: Charlie White, Penn State University. Effects on Nitrate Leaching. Because of their deep root system, rapid root extension, and heavy N feeding, radishes are excellent scavengers of residual N following summer crops (Fig. Radishes take up N from both the topsoil and from deeper soil layers, storing the N in their shoot and root biomass. With favorable fall growing conditions, radishes typically take up more than 1. N. Much higher amounts of N may be acquired when N is abundant. Early planting promotes high biomass production and associated nutrient accumulation but research at the University of Maryland has shown that late planted radishes can still take up substantial quantities of N despite low biomass production due to shifts in plant C: N ratio (Dean and Weil, 2. Figure 6. Scavenging of soil nitrate by radish. Figure credit: Ray Weil, University of Maryland. Effects on Early Spring Nitrogen. Unlike cereal rye and other small grains whose residues decompose slowly and continue to immobilize N for an extended period, radish residues decompose and release N rapidly (Fig. Timely crop establishment following radishes can result in an early boost in growth and N uptake similar to following a legume cover crop or N fertilizer application. In contrast, if planting is delayed (e. N scavenged by radishes to subsequent crops may be limited. Research at the University of Maryland found that early planting of spring crops following radish was more important on sandy soils than finer textured soils (Kremen, 2. More research is needed to identify strategies for optimizing recycling of the N scavenged by radish cover crops (e. Figure 7. Spring release of N from radish residues (FR = following radish, NC = no cover). Figure credit: Ray Weil and Amy Kremen, University of Maryland. Effects on Soil Phosphorus and Potassium. Radishes are excellent accumulators of P and K (root dry matter commonly contains more than 0. P and 4% K), and elevated levels of soil test P have been measured following radish cover cropping, particularly within 1. Cover Crop Topic Room / Learning Center / SAREThe content on this page is available as a topic brief (PDF download), Cover Crops for Sustainable Crop Rotations. Use the green Order button on this page to order free hard copies. What is a Cover Crop? A cover crop is a plant that is used primarily to slow erosion, improve soil health, enhance water availability, smother weeds, help control pests and diseases, increase biodiversity and bring a host of other benefits to your farm. Cover crops have also been shown to increase crop yields, break through a plow pan, add organic matter to the soil, improve crop diversity on farms and attract pollinators. There is an increasing body of evidence that growing cover crops increases resilience in the face of erratic and increasingly intensive rainfall, as well as under drought conditions. Cover crops help when it doesn. The yield benefit is often apparent after just one year of using cover crops and farmers will start to see other benefits, such as improved soil health, after several years of using them in crop rotation. Two years of survey results for farmers in the United States using cover crops demonstrate their yield benefits. In 2. 01. 2, corn yields increased 9. In 2. 01. 3, corn yields were 3. Whether you are just starting with cover crops, or have some experience growing them, the SARE Cover Crop Topic Room has a wealth of information you can use. Here we summarize some of that information and provide an introduction to many of the benefits of growing cover crops. To select cover crops for your operation, first identify your primary objectives for adding them to your system. Do you want to add nitrogen to your soil, increase organic matter to improve soil health, reduce erosion, provide weed control, manage nutrients, and/or conserve soil moisture? While all cover crops provide many of these benefits, some species or . Are you looking for winter cover crops to scavenge nitrogen, summer cover crops to break soil compaction, a window in a small- grain rotation to supply much needed nutrients, or even a full- year cycle to improve soil or suppress weeds? Consider creating a new rotation or modifying an existing one to accommodate your long- term objectives for planting cover crops. Also remember that there is likely no single cover crop that is right for your farm (see Cocktails or Mixtures, below). Finally, think through exactly how and when you will seed, terminate and plant into your cover crop. Do you know a reliable source for cover crop seeds, what will the weather be like, can you get into the field, do you want it to winterkill, and what labor and equipment will you need? Find information to help you answer these questions in Selection and Management, but above all, consult local expertise, including other farmers. Legume cover crops (red clover, crimson clover, vetch, peas, beans) can fix a lot of nitrogen (N) for subsequent crops, generally ranging from 5. You can usually reduce your nitrogen fertilizer inputs following a legume, but they are not very good at scavenging nitrogen that is left over after your cash crops. Legumes also help prevent erosion, support beneficial insects and pollinators, and they can increase the amount of organic matter in soil, although not as much as grasses. Legumes differ in their productivity and adaptability to soil and climatic conditions. If a legume fits your cover crop objectives, seek additional information in the Overview of Legume Cover Crops section of Managing Cover Crops Profitably or with local expertise to identify the best ones for your conditions. Non- legume cover crops include the cereals (rye, wheat, barley, oats, triticale), forage grasses (annual ryegrass) and broadleaf species (buckwheat, mustards and brassicas, including the forage radish). Non- legumes are most useful for scavenging nutrients, providing erosion control, suppressing weeds and producing large amounts of residue that adds soil organic matter. Plant a non- legume whenever a field has excess nutrients, particularly nitrogen. When planted as a fall cover crop, non- legumes consistently take up 3. If large amounts of nitrogen are left in the soil from the summer crop or due to a history of manure applications, non- legumes can scavenge upwards of 1. Depending on your conditions. To learn more about non- legume cover crops, read the Overview of Non- Legume Cover Crops section of Managing Cover Crops Profitably or consult with local expertise. Although seeding and management of cover crop mixes or . Cover crop mixtures offer the best of both worlds by combining the benefits of grasses and legumes, or using the different growth characteristics of several species to fit your needs. Compared to pure stands of legumes or non- legumes, cocktails usually produce more overall biomass and nitrogen, tolerate adverse conditions, increase winter survival, provide ground cover, improve weed control, attract a wider range of beneficial insects and pollinators, and provide more options for use as forage. However, cocktails often cost more, can create too much residue, may be difficult to seed and generally require more complex management. Find out more information about cocktails and cover crop mixes in the Grass/Legume Mixes chapter of Managing Cover Crops Profitably. One of the biggest challenges of cover cropping is to fit cover crops into your current rotations, or to develop new rotations that take full advantage of their benefits. There may be a role for cover crops in almost all rotations, but the diversity of cropping systems precludes addressing them here. Find more information by reading Crop Rotation on Organic Farms and Managing Cover Crops Profitably, reviewing the Crop Rotations page of this topic room, and consulting local expertise. Whether you add cover crops to your existing rotations or totally revamp your farming system, you should devote as much planning and attention to your cover crops as you do to your cash crops. Failure to do so can lead to failure of the cover crop and cause problems in other parts of your system. No- till farming or other conservation agriculture systems are good opportunities to plant cover crops. The cover crop mulch can increase water infiltration and also improve moisture availability by preventing evaporation. Cover crop residue helps control weeds, which is especially important in organic no- till agriculture. For resources on this subject, read the results of SARE- funded resesarch on the No- Till page of this topic room. Plant cover crops in organic farming to provide nitrogen, manage weeds and improve soil health. In organic no- till farming, use a roller- crimper to kill the cover crop and leave the mulch on the soil surface to conserve water. Or, incorporate the cover crop into the soil (sometimes called a green manure) before planting your main crop. Cover crop economics are rooted in nitrogen dynamics (how much nitrogen you save or produce with cover crops), fuel costs (the cost of nitrogen and trips across the field) and commodity prices. Given wide fluctuations in commodity and energy prices in recent years, it is difficult to generate accurate economic analyses or to predict economic returns for future growing seasons. We do know that cover crops can help you increase yield, save on nitrogen costs, reduce trips across the field and reap many agronomic benefits. Cover crops clearly improve overall soil health. Read how SARE grantees have quantified the monetary benefits of cover crops in the Economics page of this topic room. Cover crops maintain and improve soil fertility in a number of ways. Protection against soil loss from wind and water erosion is perhaps the most obvious soil benefit, but providing organic matter is a more long- term and equally important goal. Cover crops contribute indirectly to overall soil fertility and health by catching nutrients before they can leach out of the soil profile or, in the case of legumes, by adding nitrogen to the soil. Their roots can even help unlock some nutrients in the soil, converting them to more available forms. The amount and availability of nutrients from cover crops will vary widely depending on such factors as species, planting date, plant biomass and maturity at termination date, residual soil fertility, and temperature and rainfall conditions. See the Soil and Fertility Management section of this topic room or Building Soils For Better Crops for more information on building soil health by using cover crops and other practices on your farm. Evidence is mounting that cover crops help stabilize yields and improve moisture availability in the face of increasingly erratic weather. Is it too wet in the spring? Cover crops take up water (via evapotranspiration) and usually allow you onto the field earlier than if you did not have a cover crop growing. Alternatively, if facing drought or practicing dryland farming, cover crops still help boost yields while being very efficient with water use. If you use no- till farming, the cover crop mulch increases water infiltration and conserves moisture into the summer. Added carbon and root channels, in addition to increased soil pore space, help improve soil water- holding capacity. For more information on using cover crops to address erratic weather events, visit the Water Management page of this topic room. With careful attention to cultivar choice, placement and timing, cover crops can reduce infestations by insects, diseases, nematodes and weeds. Cover crops that attract and retain beneficial insects. Cover crop mulches suppress weeds and reduce splashing of soil- borne pathogens onto leaves, while some, such as sudangrass, brassicas and mustards, reduce populations of verticillium wilt and other soil pathogens. Other mulches have been shown to suppress nematodes. In Michigan, for example, some potato growers report that two years of radish improves potato production and lowers pest control costs.
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