Articoli di riviste: "Cover crop"

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London, Howard, David J. Saville, Charles N. Merfield, Oluwashola Olaniyan e Stephen D. Wratten. "The ability of the green peach aphid (Myzus persicae) to penetrate mesh crop covers used to protect potato crops against tomato potato psyllid (Bactericera cockerelli)". PeerJ 8 (7 agosto 2020): e9317. http://dx.doi.org/10.7717/peerj.9317.

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In Central and North America, Australia and New Zealand, potato (Solanum tuberosum) crops are attacked by Bactericera cockerelli, the tomato potato psyllid (TPP). ‘Mesh crop covers’ which are used in Europe and Israel to protect crops from insect pests, have been used experimentally in New Zealand for TPP control. While the covers have been effective for TPP management, the green peach aphid (GPA, Myzus persicae) has been found in large numbers under the mesh crop covers. This study investigated the ability of the GPA to penetrate different mesh hole sizes. Experiments using four sizes (0.15 × 0.15, 0.15 × 0.35, 0.3 × 0.3 and 0.6 × 0.6 mm) were carried out under laboratory conditions to investigate: (i) which mesh hole size provided the most effective barrier to GPA; (ii) which morph of adult aphids (apterous or alate) and/or their progeny could breach the mesh crop cover; (iii) would leaves touching the underside of the cover, as opposed to having a gap between leaf and the mesh, increase the number of aphids breaching the mesh; and (iv) could adults feed on leaves touching the cover by putting only their heads and/or stylets through it? No adult aphids, either alate or apterous, penetrated the mesh crop cover; only nymphs did this, the majority being the progeny of alate adults. Nymphs of the smaller alatae aphids penetrated the three coarsest mesh sizes; nymphs of the larger apterae penetrated the two coarsest sizes, but no nymphs penetrated the smallest mesh size. There was no statistical difference in the number of aphids breaching the mesh crop cover when the leaflets touched its underside compared to when there was a gap between leaf and mesh crop cover. Adults did not feed through the mesh crop cover, though they may have been able to sense the potato leaflet using visual and/or olfactory cues and produce nymphs as a result. As these covers are highly effective for managing TPP on field potatoes, modifications of this protocol are required to make it effective against aphids as well as TPP.

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Kruse, Raymond, e Ajay Nair. "Summer Cover Crops and Lettuce Planting Time Influence Weed Population, Soil Nitrogen Concentration, and Lettuce Yields". HortTechnology 26, n. 4 (agosto 2016): 409–16. http://dx.doi.org/10.21273/horttech.26.4.409.

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Cover crops can be used as a sustainable weed management tool in crop production systems. Cover crops have the ability to suppress weeds, reduce soil erosion, increase soil organic matter, and improve soil physical, chemical, and biological properties. In the north-central region of the United States, including Iowa, much cover crop research has been conducted in row crop systems, mainly with corn (Zea mays) and soybean (Glycine max) where cover crops are planted at the end of the growing season in September or October. There is little information available on the use of cover crops in vegetable cropping systems, particularly on the use of summer cover crops for fall vegetable production. The choice of the cover crop will significantly impact the entire fall vegetable production enterprise. Vegetable growers need information to identify the right cover crop for a particular slot in the cropping system and to understand how cover crops would affect weed suppression, soil properties, and successive vegetable crop yield. The time interval between cover crop termination and vegetable planting critically affects the growth and successive yield of the vegetable crop. This study investigated how short-duration summer cover crops impact weed suppression, soil properties, and ‘Adriana’ lettuce (Lactuca sativa) yield. The study also examined appropriate planting times of lettuce transplants after soil incorporation of cover crops. The experimental design was a randomized complete block split-plot design with four replications. Whole plots consisted of cover crop treatments: ‘Mancan’ buckwheat (Fagopyrum esculentum), ‘Iron & Clay’ cowpea/southernpea (Vigna unguiculata), black oats (Avena strigosa), ‘Grazex II’ sorghum-sudangrass (Sorghum bicolor ssp. drummondii), and a control (no-cover crop) where weeds were left to grow unchecked. The subplot treatment consisted of two lettuce transplanting times: planted immediately or 8 days after cover crop soil incorporation. Fall-planted butterhead lettuce was used. Data were collected on cover crop biomass, weed biomass, soil nutrient concentration, lettuce growth, and yield. All cover crops significantly reduced weed biomass during the fallow period as compared with the control treatment. Highest degree of weed suppression (90% as compared with the no-cover crop control treatment) was provided by buckwheat. Southernpea, a legume, increased soil nitrogen (N) concentration and contributed to higher lettuce yield and improved quality. Southernpea also enhanced lettuce growth and led to an earlier harvest than other treatments. Sorghum-sudangrass showed evidence of detrimental effects to the marketable lettuce crop. This was not due to N immobilization but presumably due to alleopathic properties. There is no clear pattern within any cover crop treatment that lettuce planting time following cover crop termination affects plant growth; however, planting early or soon after cover crop incorporation ensures more growing degree days and daylight, thus leading to timely harvest of a higher quality product. This study demonstrates that cover crops can successfully be integrated into vegetable cropping systems; however, cover crop selection is critical.

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Cai, Zhen, Ranjith P. Udawatta, Clark J. Gantzer, Shibu Jose, Larry Godsey e Lauren Cartwright. "Economic Impacts of Cover Crops for a Missouri Wheat–Corn–Soybean Rotation". Agriculture 9, n. 4 (24 aprile 2019): 83. http://dx.doi.org/10.3390/agriculture9040083.

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In the United States, agricultural production using row-crop farming has reduced crop diversity. Repeated growing of the same crop in a field reduces soil productivity and increases pests, disease infestations, and weed growth. These negative effects can be mitigated by rotating cash crops with cover crops. Cover crops can improve soil’s physical, chemical, and biological properties, provide ground cover, and sequester soil carbon. This study examines the economic profitability for a four-year wheat–corn–soybean study with cover crops by conducting a field experiment involving a control (without cover crops) at the Soil Health Farm in Chariton County, MO, USA. Our findings suggested that economic profitability of the cash crop is negatively affected by the cover crop during the first two years but were positive in the fourth year. The rotation with cover crops obtained the same profit as in the control group if revenue from the cash crop increased by 35% or the cost of the cover crop decreased by 26% in the first year, depending on the cost of seeding the cover crop and terminating it. This study provides insights for policymakers on ways to improve the economic efficiency of cost-share conservation programs.

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Smith, Richard G., Lesley W. Atwood, Fredric W. Pollnac e Nicholas D. Warren. "Cover-Crop Species as Distinct Biotic Filters in Weed Community Assembly". Weed Science 63, n. 1 (marzo 2015): 282–95. http://dx.doi.org/10.1614/ws-d-14-00071.1.

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Cover crops represent a potentially important biological filter during weed community assembly in agroecosystems. This filtering could be considered directional if different cover-crop species result in weed communities with predictably different species composition. We examined the following four questions related to the potential filtering effects of cover crops in a field experiment involving five cover crops grown in monoculture and mixture: (1) Do cover crops differ in their effect on weed community composition? (2) Is competition more intense between cover crops and weeds that are in the same family or functional group? (3) Is competition more intense across weed functional types in a cover-crop mixture compared with cover crops grown in monocultures? (4) Within a cover-crop mixture, is a higher seeding rate associated with more effective biotic filtering of the weed community? We found some evidence that cover crops differentially filtered weed communities and that at least some of these filtering effects were due to differential biomass production across cover-crop species. Monocultures of buckwheat and sorghum–sudangrass reduced the number of weed species relative to the no-cover-crop control by an average of 36 and 59% (buckwheat) and 25 and 40% (sorghum–sudangrass) in 2011 and 2012, respectively. We found little evidence that competition intensity was dependent upon the family or functional classification of the cover crop or weeds, or that cover-crop mixtures were stronger assembly filters than the most effective monocultures. Although our results do not suggest that annual cover crops exert strong directional filtering during weed community assembly, our methodological framework for detecting such effects could be applied to similar future studies that incorporate a greater number of cover-crop species and are conducted under a greater range of cover-cropping conditions.

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ALLISON, M. F., M. J. ARMSTRONG, K. W. JAGGARD e A. D. TODD. "Integration of nitrate cover crops into sugarbeet (Beta vulgaris) rotations. I. Management and effectiveness of nitrate cover crops". Journal of Agricultural Science 130, n. 1 (febbraio 1998): 53–60. http://dx.doi.org/10.1017/s0021859697005108.

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Between 1989 and 1993, 17 experiments tested the effect of cover crop species, sowing date and destruction date on cover crop dry matter (DM) yield, N uptake and on soil mineral nitrogen (SMN) content. All the experiments were carried out in Suffolk, Norfolk, Lincolnshire and Yorkshire on sandy-loam textured soils after crops of cereals or oilseed rape had been harvested. The largest DM yields were obtained with early sowings and averaged 1·6 t/ha. Cover crop N uptake was less dependent upon sowing date and averaged 35 kg N/ha. The average reduction in SMN was from 46 to 32 kg N/ha. Differences between cover crop species were small when compared with season/site variations.Cereal cover crop DM yields were closely related to the thermal time accumulated from the first significant rainfall after sowing, whilst the yields of non-cereal cover crops were more affected by the moisture content of the soil at sowing. The amount of SMN in the soil at sowing had little or no effect on cover crop yield. The yields of cereal cover crops were much more predictable than those of non-cereal cover crops. Water usage by cover crops was estimated to be 20 mm/t DM and large cover crops delayed the onset of leaching and reduced the amount of water leached. However, even in dry autumns and winters, soils are likely to reach field capacity before the following beet crop is sown. Due to their large C[ratio ]N ratio (20[ratio ]1) little N would be mineralized after cover crop destruction. Cover crops comprising volunteer cereals and weeds often performed as well as the other cover crops and in most cases will be the most cost-effective cover crops.

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Weston, Leslie A. "Cover Crop and Herbicide Influence on Row Crop Seedling Establishment in No-Tillage Culture". Weed Science 38, n. 2 (marzo 1990): 166–71. http://dx.doi.org/10.1017/s0043174500056320.

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The establishment and management of nine cover crops in Kentucky production systems were evaluated in field experiments over a 2-yr period. ‘Wheeler’ rye, ‘Barsoy’ barley, and ‘Tyler’ wheat cereal grains produced greater biomass (180 to 260 g/m2) than the pasture species tall fescue, creeping red fescue, and white clover (55 to 110 g/m2). ‘Kentucky 31’ tall fescue, creeping red fescue, and white clover proved most difficult to control, and significant regrowth occurred regardless of herbicide or rate applied. HOE-39866 (1.7 kg ai/ha) was effective in rapidly controlling all cover crops except tall fescue by 30 days after application. Sethoxydim and fluazifop (0.4 and 0.3 kg ai/ha, respectively) effectively controlled the cereals and two ryegrass species. Glyphosate applied at 1.1 and 2.2 kg ai/ha was also effective, while 0.6 kg ai/ha controlled only cereal grain growth adequately. After chemical control, pasture grass plots contained fewest weeds/m2with some reductions likely due to density and regrowth of the sods. Cover crops were effective in suppressing weed growth at 45 days after chemical control. However, significant weed growth existed in all cover crop plots by 60 days after kill. Row crop establishment increased linearly with increasing glyphosate rate. Cereal grain covers provided the most compatible planting situations for greatest seedling establishment, with rye and wheat providing greatest weed suppression. Generally, increased weed suppression provided by a cover crop was accompanied by reduced row crop establishment, with greatest reductions observed in pasture grass plots. Cucumber was most easily established while snap pea was most difficult.

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Oliveira, Maxwel C., Liberty Butts e Rodrigo Werle. "Assessment of Cover Crop Management Strategies in Nebraska, US". Agriculture 9, n. 6 (14 giugno 2019): 124. http://dx.doi.org/10.3390/agriculture9060124.

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Adoption of cover crops has the potential to increase agricultural sustainability in the US and beyond. In 2017, a survey was conducted with Nebraska stakeholders in an attempt to evaluate current cover crop management strategies adopted in soybean (Glycine max [L.] Merr.), field corn (Zea mays L.), and seed corn production. Eighty-two Nebraska stakeholders answered the survey, of which 80% identified themselves as growers. Eighty-seven percent of respondents manage cover crops, and the average cover crop ha planted on a per farm basis is 32%. The primary method of establishing cover crops following soybeans and field corn is drilling. In seed corn, interseeding is the main seeding strategy for cover crop establishment. Cereal rye (Secale cereale L.) appeared as the most adopted cover crop species (either alone or in mixtures with radish [Raphanus sativus L.] or hairy vetch [Vicia villosa Roth]). Over 95% of respondents utilize herbicides for cover crop termination in the spring before crop planting. Glyphosate is used by 100% of survey respondents that use herbicides for cover crop termination. The major observed impacts of incorporating cover crops into a production system according to survey respondents are reduced soil erosion and weed suppression. According to 93% of respondents, cover crops improve weed control by suppressing winter and/or summer annual weed species. The biggest challenge reported by cover crop adopters is planting and establishing a decent stand before winter. According to the results of this survey, there are different management strategies, positive outcomes, and challenges that accompany cover crop adoption in Nebraska. These results will help growers, agronomists, and researchers better guide cover crop adoption, management, and future research and education needs in Nebraska and beyond.

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Carabajal-Capitán, Sara, Andrew R. Kniss e Randa Jabbour. "Seed Predation of Interseeded Cover Crops and Resulting Impacts on Ground Beetles". Environmental Entomology 50, n. 4 (12 aprile 2021): 832–41. http://dx.doi.org/10.1093/ee/nvab026.

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Abstract Interseeding cover crops into standing grains can promote both agronomic and environmental benefits within agroecosystems. Producers must decide which cover crops are the best fit for their goals, and whether diverse cover crop mixtures provide benefits that are worth the increased seed cost. Broadcast seeding is an accessible strategy to try interseeding but can lead to patchy establishment; it is unknown how much seed loss is due to seed predators. In a two-year study, six cover crop species—planted as either single species or mixtures—were interseeded into standing corn. We evaluated seed predation at the time of seeding, agronomic impact through cover crop, and weedy biomass at the end of the season, and conservation impact through activity-density of ground beetles (Coleoptera: Carabidae). Cover crop seeds were vulnerable to seed predation, primarily by vertebrate seed predators, and seed loss varied across cover crop species. Cover crop biomass did not differ according to cover crop diversity and weedy biomass was not affected by cover crop presence or species. Cover crop diversity effects on carabid activity-density were inconsistent: carabids were higher in diverse mixtures in 1 year of the study, but only predicted by vegetative cover, not by cover crop, in the second year. Interseeding cover crops into corn has potential benefits for ground beetles, although the value of mixtures must be further explored.

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SaadatGhaleh joogh, Seyedeh Azaam, Ahmad Tobeh, Abdolghayoum Golipori e Mehran Ochi. "Management of cover crops of cold cereal, on total fresh weight, total dry weight weed, yield and yield components peppermint". Journal of Research in Science, Engineering and Technology 4, n. 01 (13 settembre 2019): 31–36. http://dx.doi.org/10.24200/jrset.vol4iss01pp31-36.

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To study the effect of cover crop and how manage cover crop an experiment was conducted in Agricultural Research Center of University of Mohaghegh Ardabili , the experiment was factorial based on complete randomized block design with three replications. winter cover crops and spring cover crops as the main factor with six levels( winter wheat, spring wheat, winter barley , spring barley, winter rye, winter rye+ winter barley) and how manage cover crop with three levels (living mulch, heading mulch, mulch with herbicide) as a second factor. For comparison, two controls (without cover crop with weeding weeds and without cover crop without weeding weeds) was aside experiments. The results showed that main effect of type cover crop on the number of branches, leaf fresh weight, leaf dry weight of peppermint and also the total dry weight of weeds and at the first stage of sampling, Had a significant impact. The main effect of management was significant for all traits measured. However, the interaction of cover crop in how management cover crop were not significant. Winter wheat highest number of branches, leaf fresh weight, leaf dry weight of peppermint, relative to other levels of cover crops. In the first stage sampling is obtained by winter rye, the lowest total weed weight relative to other levels. Spring barley, winter rye the lowest total weed dry matter to create than other cover crop. All three methods to manage of cover crops the most affected by weeds dry weight compared to control. (no weeding and no cover crop weed)

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Fajemisin, Adegboyega, Alexis Racelis e Rupesh Kariyat. "Cascading Effects of Cover Crops on the Subsequent Cash Crop Defense against the Polyphagous Herbivore Fall Armyworm (Spodoptera frugiperda)". Insects 14, n. 2 (10 febbraio 2023): 177. http://dx.doi.org/10.3390/insects14020177.

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Recent studies have started to show that the benefits of cover crops can cascade to the cash crop growing seasons. However, the impact of cover crops on the subsequent cash crop defense against herbivores is not well understood. To test this, we conducted a field and laboratory study to assess the possible cascading effects of cover crops such as Vigna unguiculata, Sorghum drummondii, Raphanus sativus, and Crotalaria juncea on the subsequent cash crop (Sorghum bicolor) defense against the notorious polyphagous herbivore fall armyworm (Spodoptera frugiperda) across three farms in the Lower Rio Grande Valley. Our field and laboratory studies showed that the cash crop planted in the cover crop treatment differentially affected S. frugiperda. More specifically, we found that cover crops have positive effects on the growth and development of S. frugiperda on the subsequent cash crop, including both larval and pupal parameters. However, our experiments on physical and chemical defenses in cash crops failed to show any significant differences between cover and control. Collectively, our results add an additional line of evidence on the effects of cover crops on pest dynamics outside the cash crop season, a key consideration for the selection and management of cover crops and cash crops, whose underlying mechanisms need to be examined further.

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Duncan, Hence, Jacob Eicher, Weston M. Bracey, Virginia R. Sykes, Christopher N. Boyer, Frank Yin, Gary E. Bates, David M. Butler e Alison R. Willette. "Is Harvesting Cover Crops for Hay Profitable When Planting Corn and Soybean in Tennessee?" Agronomy 12, n. 6 (1 giugno 2022): 1353. http://dx.doi.org/10.3390/agronomy12061353.

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Winter cover crops can improve the soil’s moisture-holding capacity, reduce soil water evaporation, and mitigate water-induced soil erosion; however, economic studies show mixed results on cover crop impacts on profits. One way to potentially increase the profits from planting cover crops is to harvest the cover crop for hay. The objective of this study was to determine the profitability of planting and harvesting cover crops when planting corn (Zea mays) or soybean (Glycine max (L.) Merr.) as a cash crop. We determined the difference in net returns among 15 cover crop species when planted before corn and soybeans. We then calculated the breakeven hay price if the cover crop was harvested. Data were collected from an experiment in Tennessee, from 2017 to 2019, at two locations. There was no difference in net returns across cover crop treatments for both corn and soybeans, thus indicating that planting a cover crop does not reduce profits. The breakeven prices for harvesting cover crops suggest that this system would not likely be profitable for corn but might be profitable if planting soybeans, depending on labor availability and local demand for hay.

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McKenzie, Sean C., Hayes B. Goosey, Kevin M. O'Neill e Fabian D. Menalled. "Integration of sheep grazing for cover crop termination into market gardens: Agronomic consequences of an ecologically based management strategy". Renewable Agriculture and Food Systems 32, n. 5 (29 settembre 2016): 389–402. http://dx.doi.org/10.1017/s1742170516000326.

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AbstractCover crops are suites of non-marketable plants grown to improve soil tilth and reduce erosion. Despite these agronomic benefits, the use of cover crops is often limited because they do not provide a direct source of revenue for producers. Integrating livestock to graze cover crops could provide both an expeditious method for cover crop termination and an alternative source of revenue. However, there has been little research on the agronomic impacts of grazing for cover crop termination, especially in horticultural market-gardens. We conducted a 3-year study comparing the effects of sheep grazing to terminate a four species cover crop (buckwheat, sweetclover, peas and beets) with those of mowing on soil quality indicators, cover crop termination efficacy, and subsequent cash-crop yields. In addition, we tested the nutritional quality of the cover crop as forage. Compared with mowing, sheep grazing did not affect soil chemistry, temperature or moisture. Our study demonstrates that sheep grazing removed more cover crop biomass than mowing at termination. The assessment of nutritional indices suggests that the four-species cover crop mixture could provide high-quality forage with a potential value of US$144.00–481.80 ha−1of direct revenue as a grazing lease. Cash-crop yields did not differ between previously grazed and previously mowed plots in the subsequent growing season. We conclude that integrating sheep grazing into market vegetable garden operations could make cover crops more economically viable without having adverse effects on subsequent cash crops.

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Mallory, Ellen B., Joshua L. Posner e Jon O. Baldock. "Performance, economics, and adoption of cover crops in Wisconsin cash grain rotations: On-farm trials". American Journal of Alternative Agriculture 13, n. 1 (marzo 1998): 2–11. http://dx.doi.org/10.1017/s0889189300007578.

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AbstractCover crop performance depends largely on management factors that must be customized to particular farm situations and, therefore, is suited for on-farm research, with farmers involved in both management and evaluation. Cover crop sequences that were successful in a research station study were tested over a variety of soils and management strategies in collaboration withfarmers. The two-year cover crop sequences consisted of a short-season crop followed by a cover crop in year one and corn in year two. The cover crops themselves were evaluated by their agronomic and economic performance and their acceptance by farmers. Four cover crop systems (companionseeded red clover, sequentially seeded hairy vetch, sequentially seeded oat, and fallow) were compared for ground cover, above-ground biomass and above-ground nitrogen yield, subsequent corn grain yield, and N fertilizer replacement value (N-FRV). Cover crops were essential for erosion control following vegetable crops and tillage, but were not necessary following small grains. Companion-seeded red clover produced the most ground cover, yielded up to 133 kg N/ha, and had a higher average N-FRV than sequentially seeded hairy vetch on sandy loam soils, but was not preferred by farmers who harvested small grain straw as well as grain. Sequentially seeded hairy vetch gave excellent cover when no-till seeded, produced more than 125 kg N/ha in half the siteyears, and had a higher average N-FRV than companion-seeded red clover on silt loam soils. First-year N-FRV for the legume cover crops averaged 67 kg N/ha over both soil types. The participating farmers indicated that their decisions to adopt cover crops would be based primarily on their need for ground cover, and secondarily on the profitability of using cover crops as an N source. However, when valued solely as an N source for the next year's crop (and not for any potential long-term benefits), cover crops were not an economical alternative to N fertilizer. We suggest focusing future cover crop research and extension efforts on outreach to farmers growing crops that do not provide sufficient ground cover, such as short-season vegetable crops, and optimizing the cover crop system to maximize its erosion control benefits and increase its profitability over N fertilizer.

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Hmielowski, Tracy. "Cover Crop Mixtures". Crops & Soils 50, n. 3 (maggio 2017): 58–59. http://dx.doi.org/10.2134/cs2017.50.0318.

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Fernando, Margaret, e Anil Shrestha. "The Potential of Cover Crops for Weed Management: A Sole Tool or Component of an Integrated Weed Management System?" Plants 12, n. 4 (8 febbraio 2023): 752. http://dx.doi.org/10.3390/plants12040752.

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Abstract (sommario):

Cover crops are an important component of integrated weed management programs in annual and perennial cropping systems because of their weed suppressive abilities. They influence weed populations using different mechanisms of plant interaction which can be facilitative or suppressive. However, the question often arises if cover crops can be solely relied upon for weed management or not. In this review we have tried to provide examples to answer this question. The most common methods of weed suppression by an actively growing cover crop include competition for limited plant growth resources that result in reduced weed biomass, seed production, and hence reductions in the addition of seeds to the soil seedbank. Cover crop mulches suppress weeds by reducing weed seedling emergence through allelopathic effects or physical effects of shading. However, there is a great degree of variability in the success or failure of cover crops in suppressing weeds that are influenced by the cover crop species, time of planting, cover crop densities and biomass, time of cover crop termination, the cash crop following in the rotation, and the season associated with several climatic variables. Several studies demonstrated that planting date was important to achieve maximum cover crop biomass, and a mixture of cover crop species was better than single cover crop species to achieve good weed suppression. Most of the studies that have demonstrated success in weed suppression have only shown partial success and not total success in weed suppression. Therefore, cover crops as a sole tool may not be sufficient to reduce weeds and need to be supplemented with other weed management tools. Nevertheless, cover crops are an important component of the toolbox for integrated weed management.

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Christoph, Kunz, Sturm Dominic J, Sökefeld Markus e Gerhards Roland. "Weed suppression and early sugar beet development under different cover crop mulches". Plant Protection Science 53, No. 3 (25 giugno 2017): 187–93. http://dx.doi.org/10.17221/109/2016-pps.

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Field experiments were conducted at two locations in 2014–2015 and 2015–2016 to investigate the weed suppressive ability of cover crop mulches in sugar beets. Three cover crops and two cover crop mixtures were tested in all four experiments. Weed densities ranged from 2 up to 210 plants/m<sup>2</sup> in Chenopodium album L. and Stellaria media (L.) Vill. as predominant species. Sinapis alba grew significantly faster than Vicia sativa, Raphanus sativus var. niger, and both cover crop mixtures. Sinapis alba, Vicia sativa, Raphanus sativus var. niger reduced weed density by 57, 22, and 15% across all locations, respectively. A mixture of seven different cover crops reduced weed emergence by 64% compared to the control plot without cover crop mulch. Early sugar beet growth was enhanced by all mulch treatments in 2015 and decelerated in 2016.

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Wortman, Sam E., Charles A. Francis, Mark A. Bernards, Erin E. Blankenship e John L. Lindquist. "Mechanical Termination of Diverse Cover Crop Mixtures for Improved Weed Suppression in Organic Cropping Systems". Weed Science 61, n. 1 (marzo 2013): 162–70. http://dx.doi.org/10.1614/ws-d-12-00066.1.

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Abstract (sommario):

Cover crops can provide many benefits in agroecosystems, including the opportunity for improved weed control. However, the weed suppressive potential of cover crops may depend on the species (or mixture of species) chosen, and the method of cover crop termination and residue management. The objective of this study was to determine the effects of cover crop mixture and mechanical termination method on weed biomass and density, and relative crop yield in an organic cropping system. A field experiment was conducted from 2009 to 2011 near Mead, NE, where spring-sown mixtures of two, four, six, and eight cover crop species were included in a sunflower–soybean–corn crop rotation. Cover crops were planted in late March, terminated in late May using a field disk or sweep plow undercutter, and main crops were planted within 1 wk of termination. Terminating cover crops with the undercutter consistently reduced early-season grass weed biomass, whereas termination with the field disk typically stimulated grass weed biomass relative to a no cover crop control (NC). The effects of cover crop mixture were not evident in 2009, but the combination of the undercutter and the eight-species mixture reduced early-season weed biomass by 48% relative to the NC treatment in 2010. Cover crops provided less weed control in 2011, where only the combination of the undercutter and the two-species mixture reduced weed biomass (by 31%) relative to the NC treatment. Termination with the undercutter resulted in relative yield increases of 16.6 and 22.7% in corn and soybean, respectively. In contrast, termination with the field disk resulted in a relative yield reduction of 13.6% in soybean. The dominant influence of termination method highlights the importance of appropriate cover crop residue management in maximizing potential agronomic benefits associated with cover crops.

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Davis, Adam S. "Cover-Crop Roller–Crimper Contributes to Weed Management in No-Till Soybean". Weed Science 58, n. 3 (settembre 2010): 300–309. http://dx.doi.org/10.1614/ws-d-09-00040.1.

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Termination of cover crops prior to no-till planting of soybean is typically accomplished with burndown herbicides. Recent advances in cover-crop roller–crimper design offer the possibility of reliable physical termination of cover crops without tillage. A field study within a no-till soybean production system was conducted in Urbana, IL, from 2004 through 2007 to quantify the effects of cover crop (cereal rye, hairy vetch, or bare soil control), termination method (chemical burndown or roller–crimper), and postemergence glyphosate application rate (0, 1.1, or 2.2 kg ae ha−1) on soybean yield components, weed–crop interference, and soil environmental variables. Biomass of weeds surviving management within a soybean crop following either a vetch or rye cover crop was reduced by 26 and 56%, respectively, in the rolled system compared to the burndown system. Soybean yield loss due to weed interference was unaffected by cover-crop termination method in soybean following a rye cover crop, but was higher in the rolled than burndown treatment in both hairy vetch and bare soil treatments. In soybean following a rye cover crop, regardless of termination method, yield loss to weed interference was unaffected by glyphosate rate, whereas in soybean following a vetch cover crop or bare soil, yield loss decreased with glyphosate rate. Variation in soybean yield among cover crops and cover-crop termination treatments was due largely to differences in soybean establishment, rather than differences in the soil environment. Use of a roller–crimper to terminate a cover crop preceding no-till soybean has the potential to achieve similar yields to those obtained in a chemically terminated cover crop while reducing residual weed biomass.

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19

Bergtold, Jason S., Patricia A. Duffy, Diane Hite e Randy L. Raper. "Demographic and Management Factors Affecting the Adoption and Perceived Yield Benefit of Winter Cover Crops in the Southeast". Journal of Agricultural and Applied Economics 44, n. 1 (febbraio 2012): 99–116. http://dx.doi.org/10.1017/s1074070800000195.

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Abstract (sommario):

The inclusion of cover crops in cropping systems brings direct and indirect costs and benefits. Farmers will adopt and utilize cover crops as long as the perceived benefit of using them is positive. This paper examines the demographic and management factors affecting the adoption and perceived benefit (in terms of improved crop yield) of using winter annual cover crops. A double selectivity model of cover crop adoption and perceived yield gain was estimated using survey data of Alabama farmers examining cover crop use and management. Results may help in understanding factors shaping farmers' perceptions, adoption, and retention of cover crops.

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20

Mangan, Francis X., e Stephen J. Herbert. "WINTER-KILLED LEGUMINOUS COVER CROPS FOR SWEET CORN". HortScience 27, n. 11 (novembre 1992): 1161f—1161. http://dx.doi.org/10.21273/hortsci.27.11.1161f.

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Field research was conducted in Deerfield, Mass. to study the effects of leguminous cover crops on sweet corn yield. Oat was planted alone and in combination with four leguminous cover crops August 8, 1990. Cover crop residue was disked once and sweet corn seeded April 23, 1991. Each cover crop combination had three rates of nitrogen added in two applications. Sweet corn seeded into stands of hairy vetch (Vicia villosa) yielded the highest of the cover crop combinations. All leguminous cover crop treatments yielded higher than oat alone or no cover crop when no synthetic nitrogen was added. Cover crop combinations were seeded again in the same field plots August 12, 1991. Oat biomass in November was greater where there had been leguminous cover crops or high rates of synthetic nitrogen. Legume growth was retarded in the plots that had previously received high nitrogen. It is thought that legume growth was reduced in the high nitrogen treatments due to increased oat growth and higher soil nitrogen levels which could inhibit root nodulation.

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21

Martinez, Lili, Pushpa Soti, Jasleen Kaur, Alexis Racelis e Rupesh R. Kariyat. "Impact of Cover Crops on Insect Community Dynamics in Organic Farming". Agriculture 10, n. 6 (8 giugno 2020): 209. http://dx.doi.org/10.3390/agriculture10060209.

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Manipulating cover crops as an integrated pest management strategy has recently gained popularity in both traditional and organic agroecosystems. However, little information is available for producers to make informed decisions about cover crop selection, management, and their potential use as a pest management tool. To address this, we conducted a two-year, four-season field experiment on the potential of various cover crops during the summer seasons of both years, followed by monocultures of cash crops during winters. We hypothesized that the cover crop treatments would attract beneficial insects and repel damaging herbivores in a species-specific manner, and the insect community dynamics would be bridged to the cash crops in the subsequent season. In addition, we hypothesized that cash crops would suffer lower herbivory damage following specific cover crop treatments. Our design comprised of three cover crops. Our results indicate that cover crops support beneficial insects during the early summer season, while the time of growing season doesnot affect herbivore abundance. Crop-specific effects were found for herbivore abundance with possible cascading effects on insect community as well as damage levels on the subsequent cash crop, but without any impact on the growth traits of the cash crop. Together, our data suggest that cover crops, when carefully selected, can be an integral part of a pest management strategy for sustainable agriculture.

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22

Garba, Ismail Ibrahim, e Alwyn Williams. "Integrating Diverse Cover Crops for Fallow Replacement in a Subtropical Dryland: Implications on Subsequent Cash Crop Yield, Grain Quality, and Gross Margins". Agronomy 13, n. 1 (16 gennaio 2023): 271. http://dx.doi.org/10.3390/agronomy13010271.

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Abstract (sommario):

Integrating cover cropping into crop–fallow rotation has been considered a key component of ecological intensification that could mitigate negative productivity and sustainability challenges associated with conventional fallow practices. However, the adoption of cover crops in water-limited environments has been limited by potential soil water and nitrogen (N) costs and resulting yield penalties. We examined the impacts of diverse cover crops on fallow soil water and mineral N dynamics and the legacy impacts on subsequent cash crop productivity and profitability. The cover crops used (forage oat—Avena sativa L. [grass], common vetch—Vicia sativa subsp. sativa L.)/fababean—Vicia faba L. [legume], forage rape—Brassica napus L. [brassica]) differed in functional traits related to growth, phenology, and soil water and N acquisition and use strategies. We found that grass-associated cover crops generally supported higher cash crop grain yield and profit than brassica- or legume-associated cover crops, mainly due to moderate biomass accumulation and water use and persistent groundcover. Cash crop grain yields increased by +19% and +23% following forage oat cover crop, with concomitant gains in gross margins of +96$ ha−1 and +318$ ha−1 for maize and winter wheat compared to conventional fallow. In contrast, maize grain yield following brassica-associated cover crops ranged from +8 to −21% and reduced gross margins by −229 to −686$ ha−1 relative to conventional fallow. Legume- and brassica-associated cover crops had the lowest mungbean and winter wheat grain yield and gross margins compared to conventional fallow and the added stubble. Cash crop yields were related to cover crop biomass production, biomass N accumulation, residue carbon to N ratio, and legacy impacts through effects on soil water availability at cash crop sowing. Given the additional grain yield and gross margin benefits following grass-associated cover crops, they may provide a potential alternative fallow soil water and N management option that could improve crop productivity and cropping system resilience in water-limited environments.

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23

Zhou, Yangxue, Lindsey Roosendaal e Laura L. Van Eerd. "Increased nitrogen retention by cover crops: implications of planting date on soil and plant nitrogen dynamics". Renewable Agriculture and Food Systems 35, n. 6 (14 novembre 2019): 720–29. http://dx.doi.org/10.1017/s1742170519000383.

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Abstract (sommario):

AbstractCover crops are frequently adopted to immobilize residual nitrogen post-harvest, thereby reducing potential N losses. However, the effectiveness of a cover crop depends on the species planting date, and other management practices. Limited information on N dynamics in cover crop systems is available specially in short-season vegetable rotations under temperate climate. From 2008 to 2010, a split-plot field experiment was carried out in a humid, temperate climate with cover crop treatment as the main plot factor [no cover crop control (NoCC), cereal rye, hairy vetch, oat, forage pea, oilseed radish (OSR) and a control with fertilizer N to the cucumber crop (NoCC + N)], and cover crop planting date as the split factor (early and late) to evaluate their impacts on cover crop biomass and N dynamics over the fall and following cucumber crop. All cover crop treatments significantly lowered soil mineral nitrogen (SMN) by 39–87% compared to the NoCC control, which was concomitant with cover crop growth and N accumulation. In the fall, SMN (0–90 cm depth) was less under the early-planted cover crops (avg. 78 kg N ha−1) compared to the late-planted (avg. 100 kg N ha−1). In April, greater plant available nitrogen (PAN, sum of SMN to 60 cm depth and plant N) with cover crops than without demonstrated N conservation over the winter and into the cucumber crop. Crop yield was equal to or better with a cover crop compared with the NoCC in both years; moreover, compared to the NoCC + N control yields were equivalent with OSR and pea. Oat, vetch and pea cover crops benefited the most by having an earlier planting date, while OSR and rye are recommended if the planting date is delayed. Although an early August planting date significantly increased plant N accumulation and SMN by November, this species-dependent interaction did not persist into the following season in yield and N accounted for in the system.

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24

Schmitt, Mattie B., Marisol Berti, Dulan Samarappuli e Joel K. Ransom. "Factors Affecting the Establishment and Growth of Cover Crops Intersown into Maize (Zea mays L.)". Agronomy 11, n. 4 (8 aprile 2021): 712. http://dx.doi.org/10.3390/agronomy11040712.

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Abstract (sommario):

In the North Central USA, intersowing cover crops into standing maize (Zea mays L.) is required to establish plants large enough to afford the benefits of a cover since there is limited favorable weather for cover crop growth after maize harvest. The objective of this study was to quantify the impacts of the planting method and time of planting of three cover crop species when grown with or without maize competition on their establishment. Experiments were conducted in three environments during 2018 and 2019. Experiments consisted of a factorial combination of timing of cover crop planting (V7 and R4 growth stage of maize), cover crop species (camelina (Camelina sativa (L.) Crantz), rye (Secale cereale L.), or radish (Raphanus sativus L.), method of sowing (drilled or broadcast), and maize removal. Initial cover crop populations were similar regardless of maize removal or stage of maize when sown, but intersown cover crops produced only 3% of the fall biomass, compared with treatments with maize-removed when sown at the V7 stage of maize and 14% when sown at the R4 stage. Limited light intensity (less than 20%) under the maize canopy was the main factor affecting interseeded cover crop development. Radish was more sensitive to shading than the other cover crops. Camelina and rye sown at the R4 stage of corn produced similar spring biomass as earlier-sown cover crops. Intersown cover crops had no negative effect on maize grain yield.

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25

Plastina, Alejandro, Fangge Liu, Fernando Miguez e Sarah Carlson. "Cover crops use in Midwestern US agriculture: perceived benefits and net returns". Renewable Agriculture and Food Systems 35, n. 1 (29 aprile 2018): 38–48. http://dx.doi.org/10.1017/s1742170518000194.

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Abstract (sommario):

AbstractDespite being generally accepted as a promising conservation practice to reduce nitrate pollution and promote soil sustainability, cover crop adoption in Midwestern US agriculture is low. Based on focus groups, surveys and partial budgets, we calculated the annual net returns to cover crop use for farmers in Illinois, Iowa and Minnesota; and elicited farmers’ perceptions about the pros and cons of incorporating cover crops to their row cropping systems. The novelty of our methodology resides in comparing each farmer's practices in the portion of their cropping system with cover crops (typically small), against their practices in the other portion of their cropping system without cover crops. The resulting comparisons, accounting for farmer heterogeneity, are more robust than the typical effects calculated by comparing indicators across cover crop users and unrelated non-adopters. Our results highlight the complicated nature of integrating cover crops into the crop production system and show that cover crops affect whole farm profitability through several channels besides establishment and termination costs. Despite farmers’ positive perceptions about cover crops and the availability of cost-share programs, calculated annual net returns to cover crops use were negative for most participants.

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26

Bergtold, Jason S., Steven Ramsey, Lucas Maddy e Jeffery R. Williams. "A review of economic considerations for cover crops as a conservation practice". Renewable Agriculture and Food Systems 34, n. 1 (31 maggio 2017): 62–76. http://dx.doi.org/10.1017/s1742170517000278.

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Abstract (sommario):

AbstractOver the past few decades, farmers have increasingly integrated cover crops into their cropping systems. Cover-crop benefits can help a farmer to achieve sustainability or reduce negative environmental externalities, such as soil erosion or chemical runoff. However, the impact on farm economics will likely be the strongest incentive to adopt cover crops. These impacts can include farm profits, cash crop yields or both. This paper provides a review of cover-crop adoption, production, risk and policy considerations from an economic perspective. These dimensions are examined through a review of cover-crop literature. This review was written to provide an overview of cover crops and their impacts on the farm business and the environment, especially with regard to economic considerations. Through increasing knowledge about cover crops, the intent here is to inform producers contemplating adoption and policy makers seeking to encourage adoption.

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27

Burgos, Nilda R., e Ronald E. Talbert. "Weed Control by Spring Cover Crops and Imazethapyr in No-till Southern Pea (Vigna unguiculata)". Weed Technology 10, n. 4 (dicembre 1996): 893–99. http://dx.doi.org/10.1017/s0890037x00040987.

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Abstract (sommario):

Studies were conducted at the Vegetable Substation in Kibler, AR, in 1992 and 1993, in the same plots, to evaluate weed suppression by spring-seeded cover crops and to determine the effects of cover crop and imazethapyr on no-till southern pea. A plot without cover, conventionally tilled before planting southern pea, served as control. Weed control treatments, applied as subplots in each cover crop, included a weedy check, handweeded check, and half and full rates of imazethapyr (0.035 and 0.07 kg/ha) followed by sethoxydim (0.22 kg/ha). Biomass of Palmer amaranth 6 WAR without herbicides, was less in Italian ryegrass and sorghum-sudangrass residues than in oat residue and no cover crop. Over the years, Palmer amaranth density increased 333% without cover crops and 28% with cover crops. Rice flatsedge density increased four to five times in oat and sorghum-sudangrass residues but remained the same in Italian ryegrass residue. In general, Italian ryegrass residue suppressed the most weeds. Oat residue was least suppressive. Italian ryegrass and sorghum-sudangrass also reduced southern pea stand. Regardless of cover crop and year, half and full rates of imazethapyr followed by sethoxydim equally reduced density of Palmer amaranth, goosegrass, large crabgrass, southwestern cupgrass, and rice flatsedge compared with the untreated check. Residual control of Palmer amaranth by imazethapyr was higher at the full rate than the reduced rate, regardless of cover crop. Half rate of imazethapyr followed by sethoxydim controlled 94 to 100% of Palmer amaranth, rice flatsedge, large crabgrass, and southwestern cupgrass late in the season, regardless of cover crop in 1992 and 1993. Southern pea yield in untilled plots with cover crops was two to three times lower than yield in plots with preplant tillage and no cover crops mostly because of reduction in crop stand in the presence of cover crops.

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28

Acharya, Jyotsna, Thomas B. Moorman, Thomas C. Kaspar, Andrew W. Lenssen e Alison E. Robertson. "Cover Crop Rotation Effects on Growth and Development, Seedling Disease, and Yield of Corn and Soybean". Plant Disease 104, n. 3 (marzo 2020): 677–87. http://dx.doi.org/10.1094/pdis-09-19-1904-re.

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Abstract (sommario):

The effects of winter cover crops on root disease and growth of corn and soybeans are poorly understood. A 3-year field experiment investigated the effect of winter cereal rye (Secale cereale L.) and winter camelina (Camelina sativa [L.] Crantz), used either in all three years or in rotation with each other, on corn (Zea mays L.) and soybean (Glycine max. [L.] Merr.) growth, root disease, and yield. Corn following a cover crop of camelina had reduced root disease, a lower Pythium population in seedling roots, and greater growth and yields compared with corn following a rye cover crop. Camelina and rye cover crops before soybean had either a positive or no effect on soybean growth and development, root disease, and yield. Moreover, Pythium clade B populations were greater in corn seedlings after a rye cover crop compared with those following a camelina cover crop, whereas clade F populations were greater on soybean seedlings following a camelina cover crop compared with seedlings following a rye cover crop. A winter camelina cover crop grown before corn had less-negative effects on corn seedling growth, root disease, and final yield than a winter rye cover crop before corn. Neither cover crop had negative effects on soybean, and the cover crop in the preceding spring had no measurable effects on either corn or soybean.

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29

Adhikari, Pradip, Nina Omani, Srinivasulu Ale, Paul B. DeLaune, Kelly R. Thorp, Edward M. Barnes e Gerrit Hoogenboom. "Simulated Effects of Winter Wheat Cover Crop on Cotton Production Systems of the Texas Rolling Plains". Transactions of the ASABE 60, n. 6 (2017): 2083–96. http://dx.doi.org/10.13031/trans.12272.

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Abstract (sommario):

Abstract. Interest in cover crops has been increasing in the Texas Rolling Plains (TRP) region, mainly to improve soil health. However, there are concerns that cover crops could potentially reduce soil water and thereby affect the yield of subsequent cash crops. Previous field studies from this region have demonstrated mixed results, with some showing a reduction in cash crop yield due to cover crops and others indicating no significant impact of cover crops on subsequent cotton fiber yield. The objectives of this study were to (1) evaluate the CROPGRO-Cotton and CERES-Wheat modules within the cropping system model (CSM) of the Decision Support System for Agrotechnology Transfer (DSSAT) for the TRP region, and (2) use the evaluated model to assess the long-term effects of growing winter wheat as a cover crop on water balances and seed cotton yield under irrigated and dryland conditions. The two DSSAT crop modules were calibrated using measured data on soil water and crop yield from four treatments: (1) irrigated cotton without a cover crop (CwoC-I), (2) irrigated cotton with winter wheat as a cover crop (CwC-I), (3) dryland cotton without a cover crop (CwoC-D), and (4) dryland cotton with a winter wheat cover crop (CwC-D) at the Texas A&M AgriLife Research Station at Chillicothe from 2011 to 2015. The average percent error (PE) between the CSM-CROPGRO-Cotton simulated and measured seed cotton yield was -10.1% and -1.0% during the calibration and evaluation periods, respectively, and the percent root mean square error (%RMSE) was 11.9% during calibration and 27.6% during evaluation. For simulation of aboveground biomass by the CSM-CERES-Wheat model, the PE and %RMSE were 8.9% and 9.1%, respectively, during calibration and -0.9% and 21.8%, respectively, during evaluation. Results from the long-term (2001-2015) simulations indicated that there was no substantial reduction in average seed cotton yield and soil water due to growing winter wheat as a cover crop. Keywords: CERES-Wheat, Cover crop, Crop simulation model, CROPGRO-Cotton, DSSAT, Seed cotton yield, Soil water.

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30

Kumar, Virender, Daniel C. Brainard e Robin R. Bellinder. "Effects of Spring-sown Cover Crops on Establishment and Growth of Hairy Galinsoga (Galinsoga ciliata) and Four Vegetable Crops". HortScience 44, n. 3 (giugno 2009): 730–36. http://dx.doi.org/10.21273/hortsci.44.3.730.

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Abstract (sommario):

Hairy galinsoga [Galinsoga ciliata (Raf.) Blake] has become a troublesome weed in vegetable crops. Field studies were conducted in 2006 and 2007 in central New York to determine the effects of: 1) spring-sown cover crops on hairy galinsoga growth and seed production during cover crop growth grown before subsequent short duration vegetable crops; and 2) cover crop residues on establishment of hairy galinsoga and four short-duration vegetable crops planted after cover crop incorporation. The cover crops [buckwheat (Fagopyrum esculentum Moench), brown mustard (Brassica juncea L.), yellow mustard (Sinapis alba L.), and oats (Avena sativa L.)] were planted in May and incorporated in early July. Lettuce (Lactuca sativa L.) and Swiss chard [Beta vulgaris var. cicla (L.) K. Koch] were transplanted and pea (Pisum sativum L.) and snap bean (Phaseolus vulgaris L.) were sown directly into freshly incorporated residues. Aboveground dry biomass produced by the cover crops was 4.2, 6.4, 6.8, and 9.7 mg·ha−1 for buckwheat, brown mustard, yellow mustard, and oats, respectively. Cover crops alone reduced the dry weight (90% to 99%) and seed production of hairy galinsoga (98%) during the cover crop-growing season compared with weedy controls. In 2006, only yellow mustard residue suppressed hairy galinsoga emergence (53%). However, in 2007, all cover crop residues reduced hairy galinsoga emergence (38% to 62%) and biomass production (25% to 60%) compared with bare soil, with yellow mustard providing the greatest suppression. Cover crop residues did not affect snap bean emergence, but reduced pea emergence 25% to 75%. All vegetable crops were suppressed by all cover crop residues with crops ranked as: pea > Swiss chard ≥ lettuce > snap bean in terms of sensitivity. The C:N ratios were 8.5, 18.3, 22.9, and 24.8 for buckwheat, brown mustard, yellow mustard, and oat residues, respectively. Decomposition rate and nitrogen release of brown mustard and buckwheat residues was rapid; it was slow for oats and yellow mustard residues. Spring-sown cover crops can contribute to weed management by reducing seed production, emergence, and growth of hairy galinsoga in subsequent crops, but crop emergence and growth may be compromised. Yellow mustard and buckwheat sown before late-planted snap beans deserve further testing as part of an integrated strategy for managing weeds while building soil health.

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31

O'Reilly, Kelsey A., John D. Lauzon, Richard J. Vyn e Laura L. Van Eerd. "Nitrogen cycling, profit margins and sweet corn yield under fall cover crop systems". Canadian Journal of Soil Science 92, n. 2 (febbraio 2012): 353–65. http://dx.doi.org/10.4141/cjss2011-065.

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Abstract (sommario):

O'Reilly, K. A., Lauzon, J. D., Vyn, R. J. and Van Eerd, L. L. 2012. Nitrogen cycling, profit margins and sweet corn yield under fall cover crop systems. Can. J. Soil Sci. 92: 353–365. In order to improve N best management practices in southwestern Ontario vegetable farming, the effect of cover crops on N dynamics in the fall and spring prior to sweet corn planting and during sweet corn season was assessed. The experiment was a split plot design in a fresh green pea – cover crop – sweet corn rotation that took place over 2 site-years at Bothwell and Ridgetown in 2006–2007 and 2007–2008, respectively. The main plot factor was fall cover crop type with five treatments including oat (Avena sativa L.), cereal rye (Secale cereale L.), oilseed radish (OSR; Raphanus sativus L. var. oleoferus Metzg Stokes), mixture OSR plus cereal rye (OSR&rye) and a no cover crop control. Compared with no cover crop, sweet corn profit margins were higher by $450 ha−1 for oat at Bothwell and $1300 and $760 ha−1 for OSR and OSR&rye, respectively, at Ridgetown. By comparing plant available N over the cover crop season, the cover crops tested were more effective at preventing N loss at Bothwell than at Ridgetown likely due to higher precipitation and sandier soil at Bothwell. Despite differences in site characteristics, cover crops did not result in increased plant available N compared with no-cover during the sweet corn season at either site, indicating that these cover crops will not provide an N credit to the following crop and growers should not modify N fertilizer applications based on cover crops.

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32

Cottney, Paul, Lisa Black, Ethel White e Paul N. Williams. "The Correct Cover Crop Species Integrated with Slurry Can Increase Biomass, Quality and Nitrogen Cycling to Positively Affect Yields in a Subsequent Spring Barley Rotation". Agronomy 10, n. 11 (12 novembre 2020): 1760. http://dx.doi.org/10.3390/agronomy10111760.

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Abstract (sommario):

The aim of this study is to identify species of cover crops that cause an increase in biomass and total nutrient accumulation in response to manure/slurry. This could improve nutrient efficiency and intensify the benefits from over-winter cover crops in arable rotations and improve following commercial crop yields. In a pot experiment, sixteen cover crops were grown for 100 days in response to slurry. Growth and nutrient (N, P, K, Mg and S) accumulation were measured, and then residue was reincorporated into the soil with spring barley (Hodeum vulgare L.) sown and harvested for yield. In response to slurry, tillage radish (Raphanus sativus L.) increased N accumulation by 101% due to a significant increase in biomass and % N (p < 0.05) over its relative control plots. Significant interactions between species and the application of slurry were found in cover crop biomass, cover crop and spring barley nutrient uptake, as well as cover crop carbon accumulation, particularly in the brassica species used. Slurry integrated with cover crops both reduced the cover crop C:N ratio and enhanced nutrient cycling compared to the control when soil mineral nitrogen (SMN) and spring barley crop N offtake were pooled. However, this was not observed in the legumes. This study shows that slurry integration with cover crops is a promising sustainable farming practice to sequester N and other macro-nutrients whilst providing a range of synergistic benefits to spring barley production when compared to unplanted/fallow land rotations. However, this advantage is subject to use of responsive cover crop species identified in this study.

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33

Peredo, J., C. Wayman, B. Whong, A. Thieme, L. R. Kline, S. Yadav, B. Eder et al. "UTILIZING LANDSAT AND SENTINEL-2 TO REMOTELY MONITOR AND EVALUATE THE PERFORMANCE OF WINTER COVER CROPS THROUGHOUT MARYLAND". ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-3/W11 (14 febbraio 2020): 125–30. http://dx.doi.org/10.5194/isprs-archives-xlii-3-w11-125-2020.

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Abstract (sommario):

Abstract. Winter cover crops have been shown to limit erosion and nutrient runoff from agricultural land. To promote their usage, the Maryland Department of Agriculture (MDA) subsidizes farmers who plant cover crops. Conventional verification of cover crop planting and analysis of subsequent crop performance requires on-the-ground fieldwork, which is costly and labor intensive. In partnership with the MDA, NASA's DEVELOP program utilized imagery from Landsat 5, Landsat 8, and the European Space Agency’s Sentinel-2 to create a decision support tool for satellite-based monitoring of cover crop performance throughout Maryland. Our teams created CCROP, an interactive graphical user interface, in Google Earth Engine which analyzes satellite imagery to calculate the normalized difference vegetation index (NDVI) of fields across the state. Linear regression models were applied to convert NDVI to estimates of crop biomass and percent green ground cover, with measure of fit (R2) values ranging from 0.4 to 0.7. These crop metrics were implemented into an interactive filtering tool within CCROP which allows users to examine cover crop performance based on a variety of growing parameters. CCROP also includes a time series analysis routine for examining the progression of NDVI throughout the spring to help determine farmer-induced termination dates of cover crops. With this decision support tool, the MDA can analyze the effectiveness of cover crops throughout the state with reduced need to manually spot-check enrolled production fields, and can identify variables influencing overall cover crop performance to optimize implementation of their winter cover crop program via adaptive management approaches.

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34

Rothrock, C. S., e W. L. Hargrove. "Influence of legume cover crops and conservation tillage on soil populations of selected fungal genera". Canadian Journal of Microbiology 34, n. 3 (1 marzo 1988): 201–6. http://dx.doi.org/10.1139/m88-038.

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Abstract (sommario):

The influence of winter legume cover crops and of tillage on soil populations of fungal genera containing plant pathogenic species in the subsequent summer sorghum crop were examined in field studies. Legume cover crops significantly increased populations of Pythium spp. throughout the sorghum crop compared with a rye cover crop or no cover crop. This stimulation of the populations of Pythium spp. was not solely due to colonization of cover-crop residue, as populations were significantly greater at the time the legume cover crop was desiccated. Removal of aboveground residue generally decreased populations of Pythium spp. in soil. Incorporation of residue by tillage increased populations of Pythium spp. at some sampling dates. Legumes differed in the magnitude of stimulation, with hairy vetch stimulating Pythium spp. more than crimson clover. Cover crop treatments did not consistently influence soil populations of Fusarium spp., Rhizoctonia solani, Rhizoctonia-like binucleate fungi, or Macrophomina phaseolina. Macrophomina phaseolina populations were significantly greater under no tillage.

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35

Kornecki, Ted S., e Stephen A. Prior. "Engine Exhaust Heat Device for Terminating Cover Crops in No-Till Vegetable Systems". Applied Engineering in Agriculture 35, n. 5 (2019): 787–93. http://dx.doi.org/10.13031/aea.13101.

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Abstract. Sustainable no-till practices utilize cover crops to protect the soil surface and to improve soil properties. Proper cover crop management is the key for successful planting of the main crop directly into cover crop residue without interfering with planting operations. In the Southern United States, the recommended time to plant cash crops into desiccated residue cover is typically three weeks after cover crop termination when the termination rate exceeds 90%; this minimizes nutrient competition between cover and cash crops. The standard method to manage cover crops is mechanical termination utilizing rollers/crimpers. This technique flattens and crimp plants to expedite termination. Another method that has been used in agriculture is to injure (desiccate) plants utilizing an external heat source. An example of utilizing an external heat source has been used in vegetable production for weed control. However, there is a need to evaluate another heat source such as exhaust heat generated by internal combustion engines (which otherwise is completely wasted) for cover crop termination effectiveness. To achieve cover crop termination with exhaust heat, a prototype was invented on board a walk-behind tractor powered by a single cylinder gasoline engine from which exhaust heat was funneled from the exhaust manifold to a perforated steel rectangular tube maintaining 204°C against a flattened cover crop to damage plant tissue. The heat pusher was equipped with electric heater strips to provide supplemental heating. Three electric heater strips (front, middle, back relative to the direction of travel) were supplied with electrical energy by a generator powered by the tractor’s PTO and generated temperatures of 379°C to 421°C with a temperature transfer efficiency of 83% to 91%. The performance of the unit with and without supplemental heating was compared with standard mechanical roller/crimper. Results demonstrated that using the exhaust heat concept can be a viable option to terminate cover crops. The exhaust heat transferring channel could be better insulated to exceed the lower 23% temperature transfer efficiency achieved by the device. Cover crop termination data during three weeks of evaluation indicated that the heat-based system was as effective as a mechanical roller/crimper. Keywords: Cereal rye, Cover crop termination, Crimson clover, Exhaust heat, Flattening cover crops, Heat transfer, Heater, Plant termination.

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36

Whalen, Derek M., Mandy D. Bish, Bryan G. Young, Aaron G. Hager, Shawn P. Conley, Daniel B. Reynolds, Lawrence E. Steckel, Jason K. Norsworthy e Kevin W. Bradley. "Evaluation of cover crop sensitivity to residual herbicides applied in the previous soybean [Glycine max (L.) Merr] crop". Weed Technology 33, n. 2 (aprile 2019): 312–20. http://dx.doi.org/10.1017/wet.2019.10.

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AbstractIn recent years, the use of cover crops has increased in U.S. crop production systems. An important aspect of successful cover crop establishment is the preceding crop and herbicide program, because some herbicides have the potential to persist in the soil for several months. Few studies have been conducted to evaluate the sensitivity of cover crops to common residual herbicides used in soybean production. The same field experiment was conducted in 2016 in Arkansas, Illinois, Indiana, Missouri, Tennessee, and Wisconsin, and repeated in Arkansas, Illinois, Indiana, Mississippi, and Missouri in 2017 to evaluate the potential of residual soybean herbicides to carryover and reduce cover crop establishment. Herbicides applied during the soybean growing season included acetochlor; acetochlor plus fomesafen; chlorimuron plus thifensulfuron; fomesafen; fomesafen plus S-metolachlor followed by acetochlor; imazethapyr; pyroxasulfone; S-metolachlor; S-metolachlor plus fomesafen; sulfentrazone plus S-metolachlor; sulfentrazone plus S-metolachlor followed by fomesafen plus S-metolachlor; and sulfentrazone plus S-metolachlor followed by fomesafen plus S-metolachlor followed by acetochlor. Across all herbicide treatments, the sensitivity of cover crops to herbicide residues in the fall, from greatest to least, was forage radish = turnip > annual ryegrass = winter oat = triticale > cereal rye = Austrian winter pea = hairy vetch = wheat > crimson clover. Fomesafen (applied 21 and 42 days after planting [(DAP]); chlorimuron plus thifensulfuron and pyroxasulfone applied 42 DAP; sulfentrazone plus S-metolachlor followed by fomesafen plus S-metolachlor; and sulfentrazone plus S-metolachlor followed by fomesafen plus S-metolachlor followed by acetochlor caused the highest visual ground cover reduction to cover crop species at the fall rating. Study results indicate cover crops are most at risk when following herbicide applications in soybean containing certain active ingredients such as fomesafen, but overall there is a fairly low risk of cover crop injury from residual soybean herbicides applied in the previous soybean crop.

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37

Gaskin, Julia W., Miguel L. Cabrera, David E. Kissel e Richard Hitchcock. "Using the cover crop N calculator for adaptive nitrogen fertilizer management: a proof of concept". Renewable Agriculture and Food Systems 35, n. 5 (8 maggio 2019): 550–60. http://dx.doi.org/10.1017/s1742170519000152.

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AbstractLegume cover crops can supply a significant amount of nitrogen (N) for cash crops, which is particularly important for organic farmers. Because N mineralization from cover crop residue depends on the amount of biomass, cover crop quality, as well as environmental conditions such as soil moisture and temperature, predicting the amount of N mineralized and the timing of release has been difficult. We have developed a Cover Crop Nitrogen Calculator based on the N subroutine of the CERES crop model and evaluated the use of the predicted N credits on yields of fall broccoli [Brassica oleracea L. (Italica group)] at a research farm and two working farms. Research farm trials consisted of a cowpea (Vigna unguiculata L. Walp.) cover crop and no cover crop treatments, each at four N rates (0N, 0.5N, 1N and 1.5N, with 1N the target N rate of 112 kg N ha−1 in 2013 and 168 kg N ha−1 in 2014 and 2015) in a randomized complete block design. On-farm trials consisted of a cowpea or sunn hemp (Crotolaria juncea L.) cover crop at four N rates (0N, 0.5N, 1N and 1.5N) and no cover crop treatment at the 1N rate in a completely randomized design. Cover crop biomass and quality (N%, carbohydrates%, cellulose% and lignin%) were measured and used with a 5-yr average soil moisture and soil temperature from a local weather station to predict an N credit. In the cover crop treatments, the N rate was modified by the predicted credit, while the no cover crop treatment received the full N fertilizer rate either as feathermeal (certified organic fields) or as urea (conventional field). At the research farm, broccoli yield increased up to the 0.5N rate, and there was no difference in yield between the no cover 0.5N rate and the cover crop 0.5N rate in 2013, 2014 and 2105. On-farm, we saw an N response in two site-years. In these site-years, there was no difference between the no cover 1N rate and the cover crop 1N rate. At the third site-year, no N response was seen. Overall, our results showed using the cover crop credit predicted by the Calculator did not reduce yields. The use of a decision support tool such as the Calculator may help farmers better manage N fertilizer when cover crops are used, and increase cover crop adoption.

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38

Acharya, Ram N., Rajan Ghimire, Apar GC e Don Blayney. "Effect of Cover Crop on Farm Profitability and Risk in the Southern High Plains". Sustainability 11, n. 24 (12 dicembre 2019): 7119. http://dx.doi.org/10.3390/su11247119.

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Cover cropping has been promoted for improving soil health and environmental quality in the southern High Plains (SHP) region of the United States. The SHP is one of the more productive areas of the country and covers a large landmass, including parts of Oklahoma, New Mexico, and Texas. This region faces challenges in sustainable crop production due to declining water levels in the Ogallala Aquifer, the primary source of water for irrigated crop production. This study examines the impact of integrating cover crops in the winter wheat (Triticum aestivum L)-based rotations on farm profitability and risk in the SHP. The study combines experimental yield data with other secondary information, including market prices, to conduct simulation analysis and evaluate the risk involved in introducing cover crops in a wheat-fallow cropping system. The results show that, due to the additional monetary costs involved, none of the cover crop options is economically viable. However, when secondary benefits (erosion control and green nitrogen) or government subsidies are included in the analysis, one of the cover crop options (peas) dominates the fallow alternative. Moreover, when the secondary benefits and a government subsidy are combined, two cover crop alternatives (peas and oats) emerge as more profitable options than leaving land fallow. These results highlight the importance of agricultural research and extension programs that are making a concerted effort to develop more productive farming techniques and increase public awareness about the long-term benefits of adopting soil health management systems such as cover cropping in the SHP region.

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39

Richards, I. R., P. A. Wallace e I. D. S. Turner. "A comparison of six cover crop types in terms of nitrogen uptake and effect on response to nitrogen by a subsequent spring barley crop". Journal of Agricultural Science 127, n. 4 (dicembre 1996): 441–49. http://dx.doi.org/10.1017/s0021859600078667.

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SUMMARYA field experiment was conducted at nine sites in England (1991–94) to compare six sown species of cover crop and natural regeneration in terms of nitrogen uptake and effect on response to applied N by a subsequent spring barley crop. The success and extent of cover crop establishment varied among sites and was insignificant in two. This may be associated with the relatively late sowing of the cover crops, the earliest site being sown on 27 August and the latest on 19 October. Dry matter (DM) yield of the sown cover crop at time of incorporation was related to sowing date, earlier sowing giving the higher yields. Maximum total DM yield and N uptake by the above-ground portion of cover crops were 1280kgDM/ha and 38 kg N/ha respectively. The extent of N uptake by the cover crops appeared to be related to the success of establishment rather than to the level of soil nitrate-N at the time of their sowing. Effects of cover crop incorporation on the subsequent spring barley were small. There was no evidence for any positive effect of the cover crop on N supply to the barley. In one trial, incorporation of forage rye significantly reduced grain yield of the barley by 0·7–1·2 t/ha compared to other cover crop species.

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40

Arias-Giraldo, Luis F., Gema Guzmán, Miguel Montes-Borrego, David Gramaje, José A. Gómez e Blanca B. Landa. "Going Beyond Soil Conservation with the Use of Cover Crops in Mediterranean Sloping Olive Orchards". Agronomy 11, n. 7 (9 luglio 2021): 1387. http://dx.doi.org/10.3390/agronomy11071387.

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Among the agricultural practices promoted by the Common Agricultural Policy to increase soil functions, the use of cover crops is a recommended tool to improve the sustainability of Mediterranean woody crops such as olive orchards. However, there is a broad range of cover crop typologies in relation to its implementation, control and species composition. In that sense, the influence of different plant species on soil quality indicators in olive orchards remains unknown yet. This study describes the effects of four treatments based on the implementation of different ground covers (CC-GRA: sown cover crop with gramineous, CC-MIX: sown cover crop with a mixture of species and CC-NAT: cover crop with spontaneous vegetation) and conventional tillage (TILL) on soil erosion, soil physicochemical and biological properties after 8 years of cover crop establishment. Our results demonstrated that the presence of a temporary cover crop (CC), compared to a soil under tillage (TILL), can reduce soil losses and maintain good soil physicochemical properties and modify greatly the structure and diversity of soil bacterial communities and its functioning. The presence of a homogeneous CC of gramineous (Lolium rigidum or Lolilum multiflorum) (CC-GR) for 8 years increased the functional properties of the soil as compared to TILL; although the most relevant change was a modification on the bacterial community composition that was clearly different from the rest of treatments. On the other hand, the use of a mixture of plant species (CC-MIX) as a CC for only two years although did not modify greatly the structure and diversity of soil bacterial communities compared to the TILL soil, induced significant changes on the functional properties of the soil and reverted those properties to a level similar to that of an undisturbed soil that had maintained a natural cover of spontaneous vegetation for decades (CC-NAT).

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41

Bangarwa, Sanjeev K., Jason K. Norsworthy, John D. Mattice e Edward E. Gbur. "Glucosinolate and Isothiocyanate Production from Brassicaceae Cover Crops in a Plasticulture Production System". Weed Science 59, n. 2 (giugno 2011): 247–54. http://dx.doi.org/10.1614/ws-d-10-00137.1.

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Brassicaceae cover crops are gaining attention as potential biofumigants for soil pest suppression because of their ability to release biologically active isothiocyanates (ITCs) and other compounds from hydrolysis of glucosinolates (GSLs). However, biofumigation potential of a Brassicaceae is related to its GSL and ITC profile and GSL to ITC conversion efficiency. Field and laboratory experiments were conducted to evaluate the biofumigation potential of seven Brassicaceae cover crops for weed control in plasticulture tomato and bell pepper. GSL concentration and composition varied among cover crops and between roots and shoots of each cover crop. Similar GSLs were produced in both years by roots or shoots of each cover crop, but GSL concentrations were variable between years. Total GSLs contributed to the soil by incorporation of Brassicaceae cover crop tissues were estimated between 47 to 452 nmol g−1soil. Highest ITC concentration was detected in soil at 3 h after cover crop incorporation, and concentration decreased at later timings. GSL to ITC conversion efficiency ranged from 1 to 39%, with variation among cover crops and between years. No injury was observed in tomato and bell pepper transplanted 1 wk after cover crop incorporation, indicating the tolerance of tomato and pepper to ITCs released by the cover crops. Early-season yellow nutsedge control from Brassicaceae cover crops was ≤ 53% at 2 wk after transplanting and declined to ≤ 18% later in the season. This research demonstrates that Brassicaceae cover crops have marginal potential for early-season weed control and cannot be used as a weed control practice in commercial tomato and bell pepper production.

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42

Luna, John M., Dan Sullivan, Amy M. Garrett e Lan Xue. "Cover crop nitrogen contribution to organic broccoli production". Renewable Agriculture and Food Systems 35, n. 1 (20 giugno 2018): 49–58. http://dx.doi.org/10.1017/s1742170518000236.

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AbstractNitrogen (N) is a difficult nutrient to manage in organic farming systems, and yield reductions related to N deficiency have been reported in organic systems. Legume-based cover crops offer opportunities for biologically fixed N; however, improved quantification of N contribution is needed for cost-effective N management. A 2-yr experiment was conducted near Corvallis, OR, USA, in 2007 and 2008 to (1) evaluate biomass production and N accumulation from selected cover crop treatments, (2) compare the effects of fall-planted cover crops on broccoli [(Brassica oleraceae L. (Italica group)] yield, (3) estimate the quantity of feather meal-N replaced by cover crops. Cover crop treatments included common vetch (Vicia sativa L.), phacelia (Phacelia tanacetifolia Benth), oats (Avena sativa L.) and the mixtures phacelia plus vetch, oats plus vetch and a no-cover crop (fallow) treatment as the control. Using feather meal as an N source, four rates of N fertilizer (0, 100, 200 and 300 kg N ha−1) were randomized within each cover crop treatment in a randomized, split-plot design. Cover crop biomass and N accumulation differed between the 2 yr of the study. In 2007, total biomass accumulation ranged from 5000 to 10,000 kg ha−1, whereas in 2008, cover crop accumulation was 1500 to 5000 kg ha−1. Biomass of both phacelia and vetch (in mixtures or as sole crops) was reduced by 80% from 2007 to 2008, whereas oat biomass and weed biomass in the fallow plots was reduced by only 40% between the 2 yr. The accumulation of N was also reduced in 2008, with vetch (either as a sole crop or in mixtures) contributing less than a third of total N produced in 2007. In 2007, vetch and vetch-based cover crop mixtures increased broccoli yield compared with the fallow, providing 100–135 kg fertilizer equivalent N ha−1. But due to decreased cover crop biomass and N accumulation in 2008, vetch and vetch-based mixtures failed to increase broccoli yield, providing <20 kg N ha−1 fertilizer equivalence. In 2007, oats grown as a sole cover crop reduced broccoli yield when no supplemental N was applied. In 2008, both phacelia and oats reduced broccoli yield at all N levels, with estimated N fertilizer equivalence values of −80 to −95 kg N ha−1. Although legume and legume mixtures increased broccoli yield in only 1 yr of the experiment, addition of vetch to the mixtures reduced yield loss in both years compared with oats and phacelia grown as sole crops.

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Higo, Masao, Yuya Tatewaki, Kento Gunji, Akari Kaseda e Katsunori Isobe. "Cover cropping can be a stronger determinant than host crop identity for arbuscular mycorrhizal fungal communities colonizing maize and soybean". PeerJ 7 (8 febbraio 2019): e6403. http://dx.doi.org/10.7717/peerj.6403.

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BackgroundUnderstanding the role of communities of arbuscular mycorrhizal fungi (AMF) in agricultural systems is imperative for enhancing crop production. The key variables influencing change in AMF communities are the type of cover crop species or the type of subsequent host crop species. However, how maize and soybean performance is related to the diversity of AMF communities in cover cropping systems remains unclear. We therefore investigated which cover cropping or host identity is the most important factor in shaping AMF community structure in subsequent crop roots using an Illumina Miseq platform amplicon sequencing.MethodsIn this study, we established three cover crop systems (Italian ryegrass, hairy vetch, and brown mustard) or bare fallow prior to planting maize and soybean as cash crops. After cover cropping, we divided the cover crop experimental plots into two subsequent crop plots (maize and soybean) to understand which cover cropping or host crop identity is an important factor for determining the AMF communities and diversity both in maize and soybeans.ResultsWe found that most of the operational taxonomic units (OTUs) in root samples were common in both maize and soybean, and the proportion of common generalists in this experiment for maize and soybean roots was 79.5% according to the multinomial species classification method (CLAM test). The proportion of OTUs specifically detected in only maize and soybean was 9.6% and 10.8%, respectively. Additionally, the cover cropping noticeably altered the AMF community structure in the maize and soybean roots. However, the differentiation of AMF communities between maize and soybean was not significantly different.DiscussionOur results suggest cover cropping prior to planting maize and soybean may be a strong factor for shaping AMF community structure in subsequent maize and soybean roots rather than two host crop identities. Additionally, we could not determine the suitable rotational combination for cover crops and subsequent maize and soybean crops to improve the diversity of the AMF communities in their roots. However, our findings may have implications for understanding suitable rotational combinations between cover crops and subsequent cash crops and further research should investigate in-depth the benefit of AMF on cash crop performances in cover crop rotational systems.

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44

Wayman, Sandra, Lisa Kissing Kucek, Steven B. Mirsky, Victoria Ackroyd, Stéphane Cordeau e Matthew R. Ryan. "Organic and conventional farmers differ in their perspectives on cover crop use and breeding". Renewable Agriculture and Food Systems 32, n. 4 (3 ottobre 2016): 376–85. http://dx.doi.org/10.1017/s1742170516000338.

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AbstractCover crops play an important role in agricultural sustainability. Unlike commodity cash crops, however, there has been relatively little cover crop breeding research and development. We conducted an online survey to evaluate: (a) the perspectives of organic and conventional farmers in the USA who use cover crops and (b) the specific cover crop traits that are important to farmers. We recruited participants from both organic and conventional agriculture networks and 69% of respondents reported that they farmed organic land. In addition to demographic data and information on management practices, we quantified farmer perspectives on four winter annual cover crops: (1) Austrian winter pea, (2) crimson clover, (3) hairy vetch and (4) cereal rye. Overall, respondents represented a wide range of states, farm sizes, plant hardiness zones and cash crops produced. Of the 417 full responses received, 87% of respondents reported that they used cover crops. The maximum amount farmers were willing to spend on cover crop seed varied by farmer type: 1% of conventional farmers versus 19% of organic farmers were willing to spend over US$185 ha−1 (US$75 acre−1). Organic and conventional farmers differed in terms of the reasons why they grew cover crops, with organic farmers placing greater value on the ecosystem services from cover crops. More organic (63%) than conventional (51%) farmers agreed that participatory breeding was important for cover crop variety development (P = 0.047). Both groups shared strong support for cover crop research and considered many of the same traits to be important for breeding. For the legume cover crops, nitrogen fixation was considered the most important trait, whereas winter hardiness, early vigor, biomass production and weed suppression were the most important traits for cereal rye. Our results illustrate common interests as well as differences in the perspectives between organic and conventional farmers on cover crops and can be used to inform nascent cover crop breeding efforts.

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45

Zablotowicz, Robert M., Krishna N. Reddy, L. Jason Krutz, R. Earl Gordon, Ryan E. Jackson e Leslie D. Price. "Can Leguminous Cover Crops Partially Replace Nitrogen Fertilization in Mississippi Delta Cotton Production?" International Journal of Agronomy 2011 (2011): 1–9. http://dx.doi.org/10.1155/2011/135097.

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Petroleum prices impact cotton nitrogen (N) fertilization cost. A field study was conducted from 2005 to 2007 to assess the interactions of cover crop (none, Austrian winter pea (Pisum sativumspp.arvense) or hairy vetch (Vicia villosaRoth)) and N fertilization (0, 67 or 134 kg N/ha applied at planting) on N availability and cotton yield under reduced-tillage management. Nitrogen content in desiccated residues averaged 49, 220, and 183 kg N/ha, in no cover crop, Austrian winter pea, and hairy vetch, respectively. Seventy percent of N in the above ground cover crop was derived from biological N fixation. In 2005, cover crops decreased cotton yield, while fertilizer N had no effect. In 2006, cover crops did not affect yield, but yield was positively correlated with N rate. In 2007, in no N plots, cotton yields were 65% higher in cover crops than in no cover crop. However, yield from N fertilized cover crop plots were similar to N fertilized no cover plots. These results indicate that leguminous cover crops can provide over 150 kg N/ha, but this N may not be as effective as fertilizer N for lack of synchronization between cotton N requirements and N release from residues.

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46

GARWOOD, T. W. D., D. B. DAVIES e A. R. HARTLEY. "The effect of winter cover crops on yield of the following spring crops and nitrogen balance in a calcareous loam". Journal of Agricultural Science 132, n. 1 (febbraio 1999): 1–11. http://dx.doi.org/10.1017/s0021859698006169.

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The recovery of nitrogen ‘retained’ through cover crop uptake, delayed ploughing and immobilization by straw was assessed in a spring cropping rotation on a chalk loam in Eastern England (1989–96). The effect of annual cover cropping on yield of the subsequent spring crops and on the soil N balance was also investigated. The recovery of retained N was in part dependent upon cover crop management. Late August-sown cover crops which were incorporated in February/March tended to reduce spring crop yields and crop N offtake. Adverse effects on soil N supply, seedbed conditions and soil water reserves were not in evidence and so an allelopathic effect from the decomposition of the rye cover crop, previously reported by others, may be responsible for the reduction in yield of spring crops. When the cover crops were drilled later and their early destruction was followed by a short fallow period, spring crop yields and N offtake were increased. The soil N balance indicated that over the course of the experiment there was a positive N input to the system due to continuous cover cropping. This input may be held as immobilized organic N, in which case it could be made available to subsequent crops over a number of years or lost via other routes. Nitrate concentrations in drainage water increased with the number of years under cover cropping.

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Baraibar, Barbara, Mitchell C. Hunter, Meagan E. Schipanski, Abbe Hamilton e David A. Mortensen. "Weed Suppression in Cover Crop Monocultures and Mixtures". Weed Science 66, n. 1 (2 ottobre 2017): 121–33. http://dx.doi.org/10.1017/wsc.2017.59.

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Interest in planting mixtures of cover crop species has grown in recent years as farmers seek to increase the breadth of ecosystem services cover crops provide. As part of a multidisciplinary project, we quantified the degree to which monocultures and mixtures of cover crops suppress weeds during the fall-to-spring cover crop growing period. Weed-suppressive cover crop stands can limit weed seed rain from summer- and winter-annual species, reducing weed population growth and ultimately weed pressure in future cash crop stands. We established monocultures and mixtures of two legumes (medium red clover and Austrian winter pea), two grasses (cereal rye and oats), and two brassicas (forage radish and canola) in a long fall growing window following winter wheat harvest and in a shorter window following silage corn harvest. In fall of the long window, grass cover crops and mixtures were the most weed suppressive, whereas legume cover crops were the least weed suppressive. All mixtures also effectively suppressed weeds. This was likely primarily due to the presence of fast-growing grass species, which were effective even when they were seeded at only 20% of their monoculture rate. In spring, weed biomass was low in all treatments due to winter kill of summer-annual weeds and low germination of winter annuals. In the short window following silage corn, biomass accumulation by cover crops and weeds in the fall was more than an order of magnitude lower than in the longer window. However, there was substantial weed seed production in the spring in all treatments not containing cereal rye (monoculture or mixture). Our results suggest that cover crop mixtures require only low seeding rates of aggressive grass species to provide weed suppression. This creates an opportunity for other species to deliver additional ecosystem services, though careful species selection may be required to maintain mixture diversity and avoid dominance of winter-hardy cover crop grasses in the spring.

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Hill, Erin C., Karen A. Renner, Christy L. Sprague e Adam S. Davis. "Cover Crop Impact on Weed Dynamics in an Organic Dry Bean System". Weed Science 64, n. 2 (giugno 2016): 261–75. http://dx.doi.org/10.1614/ws-d-15-00114.1.

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Weed suppression is one possible benefit of including cover crops in crop rotations. The late spring planting date of dry beans allows for more growth of cover crops in the spring. We assessed the influence of cover crops on weed dynamics in organic dry beans and weed seed persistence. Medium red clover, oilseed radish, and cereal rye were planted the year before dry beans; a no-cover-crop control was also included. After cover-crop incorporation, common lambsquarters, giant foxtail, and velvetleaf seeds were buried in the red clover, cereal rye, and no-cover control treatments and then retrieved 0, 1, 2, 4, 6, and 12 mo after cover-crop incorporation. Dry beans were planted in June and weed emergence and biomass measured. Eleven or more site-years of data were collected for each cover-crop treatment between 2011 and 2013, allowing for structural equation modeling (SEM), in addition to traditional analyses. Cereal rye residue increased giant foxtail and velvetleaf seed persistence by up to 12%; red clover decreased common lambsquarters seed persistence by 22% in 1 of 2 yr relative to the no-cover-crop control. Oilseed radish and incorporated cereal rye rarely reduced weed densities. When red clover biomass exceeded 5 Mg ha−1, soil inorganic N was often higher (5 of 6 site-years), as were weed density and biomass (5 and 4 of 12 main site sample times, respectively). Using SEM, we identified one causal relationship between cover-crop N content and weed biomass at the first flower stage (R1), as mediated through soil N at the time of dry bean planting and at the stage with two fully expanded trifoliates. Increasing cover-crop C : N ratios directly reduced weed biomass at R1, not mediated through changes in soil N. Cover crops that make a significant contribution to soil N may also stimulate weed emergence and growth.

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Carr, Patrick M., Randy L. Anderson, Yvonne E. Lawley, Perry R. Miller e Steve F. Zwinger. "Organic zero-till in the northern US Great Plains Region: Opportunities and obstacles". Renewable Agriculture and Food Systems 27, n. 1 (19 ottobre 2011): 12–20. http://dx.doi.org/10.1017/s174217051100041x.

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AbstractThe use of killed cover crop mulch for weed suppression, soil erosion prevention and many other soil and crop benefits has been demonstrated in organic no-till or zero-till farming systems in eastern US regions and in Canada. Implements have been developed to make this system possible by terminating cover crops mechanically with little, if any, soil disturbance. Ongoing research in the US northern Great Plains is being conducted to identify cover crop species and termination methods for use in organic zero-till (OZ) systems that are adapted to the crop rotations and climate of this semi-arid region. Current termination strategies must be improved so that cover crop species are killed consistently and early enough in the growing season so that subsequent cash crops can be grown and harvested successfully. Delaying termination until advanced growth stages improves killing efficacy of cover crops and may provide weed-suppressive mulch for the remainder of the growing season, allowing no-till spring seeding of cash crops during the next growing season. Excessive water use by cover crops, inability of legume cover crops to supply adequate amounts of N for subsequent cash crops and failure of cover crops to suppress perennial weeds are additional obstacles that must be overcome before the use of killed cover crop mulch can be promoted as a weed control alternative to tillage in the US northern Great Plains. Use of vegetative mulch produced by killed cover crops will not be a panacea for the weed control challenges faced by organic growers, but rather one tool along with crop rotation, novel grazing strategies, the judicious use of high-residue cultivation equipment, such as the blade plow, and the use of approved herbicides with systemic activity in some instances, to provide organic farmers with new opportunities to incorporate OZ practices into their cropping systems. Emerging crop rotation designs for organic no-till systems may provide for more efficient use of nutrient and water resources, opportunities for livestock grazing before, during or after cash crop phases and improved integrated weed management strategies on organic farms.

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Sanders, D. C., G. D. Hoyt, J. C. Gilsanz, J. M. Davis, J. T. Garrett, D. R. Decoteau, R. J. Dufault e K. D. Batal. "Cover Crops and N Rates Influence Sweetpotato Production". HortScience 31, n. 4 (agosto 1996): 611e—611. http://dx.doi.org/10.21273/hortsci.31.4.611e.

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`Jewel' sweetpotato was no-till planted into crimson clover, wheat, or winter fallow. Then N was applied at 0, 60, or 120 kg·ha–1 in three equal applications to a sandy loam soil. Each fall the cover crop and production crop residue were plowed into the soil, beds were formed, and cover crops were planted. Plant growth of sweetpotato and cover crops increased with N rate. For the first 2 years crimson clover did not provide enough N (90 kg·ha–1) to compensate for the need for inorganic N. By year 3, crimson clover did provide sufficient N to produce yields sufficient to compensate for crop production and organic matter decomposition. Soil samples were taken to a depth of 1 m at the time of planting of the cover crop and production crop. Cover crops retained the N and reduced N movement into the subsoil.

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