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Overwintered cover crops mechanically terminated into mulch can be a weed management tool for reduced-tillage organic agriculture. However, the impacts of management options for cover cropping are not well understood, including cover crop variety, termination timing and termination method. In a field experiment, conducted in 2012 and 2013 in Wester...
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Mechanical cover crop (CC) termination can reduce tillage in organic rotations, but research is needed to develop recommendations for producers in the upper Midwest, U.S.A. Field studies were conducted near Concord, NE, U.S.A., in 2008–2009 and 2009–2010. This study compared no-till [roller/crimper (CRIMP) and broadcast propane flame (FLAME)] and s...
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... Roller crimping is a cover crop termination method that severs or creases the aboveground vegetation, eventually leading to the death and decomposition of the remaining surface mulch. Rye is effectively terminated with a roller-crimper when it is performed during its reproductive stage, between late anthesis and early milk (Ashford and Reeves 2003;Carr et al. 2013; Keene et al. 2017;Mirsky et al. 2009;Wayman et al. 2014). In Canada, this stage typically occurs between late May and early June; however, the optimal timing of roller crimping varies depending on environmental conditions and rye cultivars, making it difficult to provide generalized recommendations. ...
Fall sown cereal rye has gained popularity as a cover crop in vegetable production due to its weed-suppressive capabilities. However, previous research has shown that replacing preemergence and/or postemergence herbicide applications with roller-crimped rye has variable success at controlling weeds and maintaining vegetable cash crop yields. The objective of this research was to test roller-crimped rye in sweet corn production to determine whether it can provide season-long weed control and maintain sweet corn yield. Two rye cultivars (early vs. standard maturity) were compared at three seeding rates (150, 300, and 600 seeds m ⁻² ) for their effect on weed control and sweet corn yield. The trial was conducted at Harrow, ON, and St. Jean-sur-Richelieu, QC, from 2019 to 2021 and at Agassiz, BC, in 2019 and 2021. Results suggest that, although the early maturing cultivar allowed for earlier roller crimping in some locations, it was inferior at weed control and resulted in lower sweet corn yield than local standard cultivars. The average rye biomass was lower than the current literature recommendations, and the resulting level of weed control was not high enough to prevent sweet corn yield loss in cover crop treatments. Weed control provided by roller-crimped rye peaked between crimping and eight weeks after crimping and was highest in the standard cultivars sown at 300 and 600 seeds m ⁻² . Preliminary testing of supplemental postemergence weed control showed evidence for sweet corn yields comparable to the weed-free no-cover crop check. However, more research is needed. Overall, it was found that with the cultivars and seeding rates tested, roller-crimped rye is not a suitable stand-alone weed control option in sweet corn. Given the benefits of cover crops, further research should evaluate its potential as a component of an integrated weed management program.
... Soil C and N pools have been found to increase when cover crops are included in rainfed cropping systems (Hao et al. 2023), but responses can be variable depending on weather conditions (Blanco-Canqui et al. 2013), cover crop composition (Dube et al. 2012), duration of stand length (Alonso-Ayuso et al. 2014), and termination method (Wayman et al. 2015). Results from this study did not detect a positive effect from cover crops on SOC, total N, and POM-C or N, thereby rejecting the first null hypothesis. ...
Crop rotations in the northern Great Plains of North America increasingly include corn ( Zea mays L.) and soybean ( Glycine max (L.) Merr.). Use of cover crops, while less extensive, is also increasing given their purported agronomic and environmental benefits. To date, soil responses to the inclusion of corn, soybean, and cover crops in rainfed cropping systems have not been well documented in the region. Therefore, soil properties were evaluated 6 years after establishment of three crop rotations (spring wheat ( Triticum aestivum L.)–soybean (SW–S), spring wheat–corn–soybean (SW–C–S), and spring wheat–corn–cover crop (SW–C–cc)) each split by no and minimum tillage on a Dark Brown Chernozem near Mandan, ND, USA. Soil responses to treatments were subtle and exclusive to the 0–7.6 cm depth. Soil pH was lower in SW–S than SW–C–cc (5.28 vs. 5.48; P = 0.05), SO 4 -S was greater under SW–C–cc than SW–C–S (13.4 vs. 11.6 g S kg ⁻¹ ; P = 0.03), exchangeable K was greater under SW–C–S and SW–C–cc than SW–S (0.83 cmol kg ⁻¹ vs. 0.52 cmol kg ⁻¹ ; P = 0.05), and water-stable aggregates were greater in SW–S than SW–C–S (26% vs. 19%; P = 0.08). Soil organic carbon (SOC) and total N did not differ among crop rotations or between tillage treatments, while particulate organic matter N was greater under no tillage compared to minimum tillage ( P = 0.08). Between 2012 and 2018, soil pH decreased and SOC increased under SW–C–S. Frequent monitoring of near-surface soil conditions in rotations with soybean every other year is recommended. Furthermore, innovative management practices are needed to enhance soil C and N fractions in rotations with full-season cover crops.
... They found greater plant available N under hairy vetch than under either control or crimson clover, with peak soil N occurring between 4 and 6 wk after roll kill. In a different study, Wayman et al. (2015) reported that cover crop variety influenced cover crop biomass, and soil nitrate -N and that termination time did not influence plant N concentration or the C:N ratio. In this study, over 3 years, there was a significant increase in the concentration of available phosphorus (P) ranging from the highest amount of 53.2 mg kg −1 (sickle mowed) to the lowest of 21 mg kg −1 for control treatments. ...
Termination methods and the timing of the termination of the cover crops are critical factors determining the efficacy of cover crops in improving soil fertility and quality. We hypothesized that different termination methods will produce varying quantities of organic residue which will affect microbial diversity and thereby nutrient cycling and availability. The objective of this study was to compare termination methods (roller-crimper, flail mowing , rotary mowing, sickle bar mowing, and occultation using black tarps) for fall-grown cover crop combination (hairy vetch-cereal rye) under organic vegetable production. Field experiments were carried out in three consecutive years (2018-2021) and soil samples were collected from 0 to 15 cm and processed for analysis. Soil organic matter content, nutrients, health parameters, enzymes, and microbial diversity were measured. Flail mowing significantly enhanced the potentially mineralizable nitrogen, available phosphorus, and active carbon. Total Phospholipid Fatty Acid (PLFA) analysis showed a 24% increase for flail mowed, 17% for rotary mowed, and 15% for sickle bar mowed termination methods. There was a significant increase in active carbon content which ranged from 38.9% (rotary mowed), 25.4% (sickle bar mowed), 23.5% (flail mowed), 16.4% for crimper rolled method, and with 2.8% (occultation) respectively. Individual termination methods had varying effects on select enzyme activities. Results indicated that integrating cover crops has the potential to modify soil microbial community structure and increase soil enzyme activities. In this study, flail mowing appeared to be a good method for managing cover crops of choice in terms of soil microbial functionality and fertility. ARTICLE HISTORY
... CC biomass production is often used as an indicator of the capacity to suppress weeds (Brennan and Smith, 2005;Wayman et al., 2015) due to competition for resources (Finney et al., 2016). Also, successful and highly productive CC need a fast initial growth to reach the highest leaf area index to maximize solar radiation interception (Elhakeem et al., 2021). ...
Cover crops effect on weed supression in a dry subhumid region of Argentina
... the findings of Wayman et al. (2015) who reported a 19% weed coverage on a 9 tons DM ha −1 of a roller-crimped rye cover crop, compared to an 81% weed coverage observed in their weediest control. In 2021 the cover crop (3.4 ton DM ha −1 ) effect on the weed ground coverage was less evident. ...
The irrigated cropping systems in South Europe could benefit from soybean [Glycine max (L.) Merr.] introduction in their maize (Zea mays L.)‐based crop rotations. However, sustainable weed management strategies are needed for soybean growers under Mediterranean irrigated conditions. This work aimed to assess the weed control efficacy, and the soybean performance, of alternative management practices for single‐ and double‐cropped soybean. Two field experiments were carried out in northeast Spain in the period 2019–2021. Row width narrowing (75–37.5 cm), herbicide application (yes/no), and roller‐crimped rye [Secale cereal (L.) M.Bieb.] cover crop (yes/no) were assessed in the single cropping system experiment (SCS). In the barley‐soybean double cropping system experiment (DCS), row width narrowing and herbicide application were assessed. In the SCS, the presence of rye cover crop reduced weed biomass up to 92% compared to the controls without herbicide and cover crop in 2020. In 2021, no effect of the cover crop on weed pressure was found due to the low amount of rye biomass accumulated (11.8 and 3.4 ton DM ha⁻¹ in 2020 and 2021, respectively). In the DCS, herbicide application attained the expected weed control. Row width narrowing to 37.5 cm did not have an impact on weed pressure nor on soybean yield in either experiment. We concluded that herbicide reduction for single‐cropped soybean under Mediterranean irrigated conditions can be achieved by roller‐crimping a rye cover crop, provided enough rye biomass is accumulated. In the DCS, our results indicated that further research is needed to find alternatives to chemical weed control.
... Adeux et al. (2021) showed that cover crops had no effect on weeds in the subsequent crops when cover crops were terminated by tillage and/or when in-crop weed management relied on herbicides, and concluded that intensive weed management could override the potential effect of cover crops on weeds in the subsequent crops. Alternative cover crop termination methods such as mowing or rolling have been investigated (Carrera et al., 2004;Wayman et al., 2014;Büchi et al., 2020) and are reported to be as efficient in reducing weed biomass in the subsequent crop as herbicide-use or tillage (Osipitan et al., 2018). In no-till systems, mulch resulting from unburied cover crop biomass can limit germination of weed species and act as a physical barrier against early weed establishment (Teasdale and Mohler, 2000). ...
The carry-over effect of cover crops on weeds and crop productivity in the subsequent crops has been related to cover crop composition and cover crop termination methods but their interaction with soil resource availability remains poorly documented, as well as the relative importance of each of these factors. This study investigated the effect of cover crop management (i.e. cover crop mixture, fertilisation, irrigation, termination method and their combinations) on weed biomass and crop productivity in two subsequent crops (spring barley followed by winter linseed). We hypothesised that cover crop management could affect productivity of the subsequent crops through both weed suppression and nitrogen supply. Two experiments spanning a duration of two years were setup , on two different fields in two different years, to investigate the effect of cover crop mixture (2 or 8 species including or not legume species, plus a bare soil control), water and nitrogen availability at cover crop sowing and cover crop termination methods (rolling, herbicide-use and winter-kill control) on weed biomass and crop productivity of the two subsequent unweeded, unfertilised and directly seeded crops. Weed biomass and crop productivity in both subsequent crops were affected by multiple interactions between cover crop mixture, soil resource availability, cover crop termination method and experiment. In experiment 1, combinations of cover crop management alternative to the reference (i.e. bare soil, without fertilisation and irrigation, winter-killed) mainly showed beneficial carry-over effects (i.e. lower weed biomass and higher crop productivity) in the subsequent spring barley while having no effect in winter linseed. In experiment 2, alternative combinations of cover crop management mainly showed no effects or detrimental carry-over effects (i.e. higher weed biomass and lower crop productivity) in spring barley while having some positive effects in winter linseed (i.e. only when cover crops were terminated with herbicide-use). Crop productivity was mainly affected by weed biomass which was significantly reduced almost only when cover crops were terminated with herbicide-use. Crop productivity was also affected but to a lesser extent by cover crop soil-mediated effects (e.g. nitrogen supply). These results highlight complex interactions between cover crop management and environmental conditions on the carry-over effects of cover crops in the subsequent crops. Cover crops may not play an essential role for weed management in no-till and herbicide-free systems, particularly at low levels of cover crop biomass production.
... Cover crops used as a green manure have the potential to build soil organic matter, improve soil microbial activity (Finney et al., 2017;Wallander et al., 2021), stabilize or increase yields (Lu et al., 2000;Bergtold et al., 2005;Snapp et al., 2005), reduce weed populations (Ngouajio et al., 2003;Lawson et al., 2015) and replace inorganic fertilizer through biological fixation (Tonitto et al., 2006;Wayman et al., 2014;Janke et al., 2017). Hairy vetch (Vicia villosa) has among the highest nitrogen fixation rates when compared to other legume cover crops (Parr et al., 2011). ...
High-tunnel (HT) systems have been shown to effectively improve yields, fruit quality and profitability. In order to maximize returns on investment, HTs are frequently planted successively with both winter and summer cash crops and may include >2 crop cycles per year in some climates. The intense cultivation strategies used in HT systems necessitate increased tillage and nutrient demands posing challenges for soil health, environmental quality and long-term economic sustainability, particularly among organic growers. Seasonal rotations that incorporate fertility-building cover crops, such as legumes and other green manures, have the potential to build soil organic matter, improve crop yield and reduce applications of animal manure and/or compost. The economic impact of cover crop use in HT production systems poses important implications for organic growers. In this study, we present three partial budget analyses to quantify the economic benefits from a leguminous winter cover crop–tomato cash crop rotation in HTs across three regions. Data used in the economic analysis come from multi-year organic HT field trials in Kansas (2016–2019), Kentucky (2016–2019) and Minnesota (2016–2020). Direct financial benefits from hairy vetch ( Vicia villosa ) cover crop N credits were observed but not sufficient to offset the direct and indirect costs of the cover crop practice. A winter cover crop used in organic HT vegetable systems results in negative financial benefits to producers even with conservation incentive payments. These results highlight challenges for organic growers who are required under the USDA National Organic Program to incorporate soil building practices as part of their rotation schedule. The findings will also be of interest to policy makers as they refine cost-share offerings and programming to incentivize cover crop adoption as a conservation strategy.
... A study compared the chemical, mechanical, and chemical + mechanical termination methods of cover crop termination and their effect on cotton (Gossypium hirsutum) emergence and yield, and reported some differences in the crop emergence but no effect on yield [42]. Another study compared two different mechanical methods of cover crop termination on mulch, weed cover and nitrogen but not on crop yield [43]. Kornecki and Kichler [44] compared different cover crop terminations with different roller-crimper types and their effect on the cantaloupe (Cucumis melo) yield, but no comparison was made with other cover crop termination methods. ...
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.
... Termination methods range from aggressive tillage (e.g. moldboard or chisel plowing) which incorporates most or all of the cover crop biomass into the soil, to roller-crimping or herbicide spraydown which leaves a layer of cover crop mulch on the soil surface with minimal incorporation (25)(26)(27)(28). Generally speaking, late-terminated cover crops accumulate more biomass and biomass N than early-terminated cover crops. ...
Summer-seeding legume cover crops can reduce erosion, mitigate nitrate leaching losses during the non-growing season, and provide bio-accumulated nitrogen (N) to the following crop. Very little information is available, however, on the most effective methods for terminating summer-seeded cover crops, or on the amount of N they can provide to subsequent crops. We therefore evaluated the impacts of selected legume cover crops and cover crop termination-tillage methods on corn (Zea mays L.) N credit and grain yield in a soybean (Glycine max Merr.) - winter wheat (Triticum aestivum L.)/cover crop - corn rotation over 3 consecutive years on a clay loam soil in southwestern Ontario. The cover crops were summer-seeded after wheat harvest, and included hairy vetch (Vicia villosa L. Roth), red clover (Trifolium pratense L.), white clover plus crimson clover mix (incarnatum and Trifolium alba L.), and a no cover crop control (CK). The cover crops were nested within termination-tillage method, including moldboard plow-down in fall, and herbicide spray-down in spring under strip-tillage or no-tillage then corn planting. Nitrogen fertilizer to corn was applied via side-dress at 200 kg N ha-1 to the CKs, and at 100 kg N ha-1 to the cover crops. Averaged over 3 years, above-ground biomass N level followed the pattern: hairy vetch > white clover plus crimson clover mix > red clover for fall plow-down termination. There were no significant differences in cover crop biomass N levels for spring termination. Corn response to cover crop was significantly affected by termination-tillage method and cover crop species, with poor corn stands after no-tillage, red clover and white plus crimson clover. Fall plow-down termination provided a range in N credit of 80-85 kg N ha-1, which was significantly greater than the N credit under herbicide spray-down in spring. Under spring strip-tillage and no-tillage, hairy vetch produced significantly greater corn grain yields than red clover and white plus crimson clover mix.
... Barley cover crops can suppress weeds with annual lifecycles such as annual sowthistle (Sonchus oleraceus), barnyardgrass (Echinochloa crus-galli), common groundsel (Senecio vulgaris) and yellow foxtail (Setaria glauca) (Alonso-Ayuso et al., 2018;Creamer et al., 1996;Dhima et al., 2006), as well as weeds with perennial lifecycles including bermudagrass (Cynodon dactylon) (Valencia-Gredilla et al., 2020). Fall-sown barley cover crops generally outcompete winter weeds, resulting in very little weed biomass at the time of cover crop termination (Silva, 2014;Wayman et al., 2014), although weed suppression ability can differ among barley varieties (Christensen, 1995). ...
... crop because the amount of rye biomass in this study was consistent with, or greater than, aboveground dry biomass for overwintered rye in previous studies (Bavougian et al., 2019;Toom et al., 2019;Moore and Mirsky, 2020;Baxter et al., 2021). However, rye biomass in our study was less than the amount of rye biomass reported by Wayman et al. (2014Wayman et al. ( , 2015 who studied fall-seeded cover crops under a cool summer Mediterranean climate (western Washington, USA) at a study site that received approximately 76 cm of precipitation over 132 to 140 days during cover crop growing seasons (Washington State University, 2022). The relatively high amount of biomass for rye grown under frequent precipitation in Wayman et al. (2014), and the relatively low amount of biomass for rye in our study, further suggests that rye cover crops are better suited for environments with plentiful moisture. ...
... However, rye biomass in our study was less than the amount of rye biomass reported by Wayman et al. (2014Wayman et al. ( , 2015 who studied fall-seeded cover crops under a cool summer Mediterranean climate (western Washington, USA) at a study site that received approximately 76 cm of precipitation over 132 to 140 days during cover crop growing seasons (Washington State University, 2022). The relatively high amount of biomass for rye grown under frequent precipitation in Wayman et al. (2014), and the relatively low amount of biomass for rye in our study, further suggests that rye cover crops are better suited for environments with plentiful moisture. This suggestion is consistent with Baxter et al. (2021) who studied five cover crops and determined that rye exhibited the greatest increase in biomass from irrigation. ...
Adoption of cover crops in arid agroecosystems has been slow due to concerns regarding limited water resources and possible soil moisture depletion. In irrigated organic systems, potential ecosystem services from cover crops also must be considered in light of the concerns for water conservation. A constructive balance could be achieved with fall-sown small grain cover crops; however, their impacts on irrigated organic systems are poorly understood. Our first objective was to determine the ability of fall-sown small grains [cereal rye ( Secale cereale L), winter wheat ( Triticum aestivum L.), barley ( Hordeum vulgare L.) and oat ( Avena sativa L.)] to suppress winter weeds in an irrigated, organic transition field in the southwestern USA. Small grains were planted following the legume sesbania ( Sesbania exaltata (Raf.) Rydb. ex A.W. Hill) during Fall 2012 and Fall 2013. In Spring 2013 and 2014, weed densities and biomass were determined within each cover crop treatment and compared against unplanted controls. Results indicated that both barley and oat were effective in suppressing winter weeds. Our second objective was to compare weed suppression and soil moisture levels among seven barley varieties developed in the western United States. Barley varieties (‘Arivat’, ‘Hayes Beardless’, ‘P919’, ‘Robust’, ‘UC603’, ‘UC937’, ‘Washford Beardless’) were fall-sown in replicated strip plots in Fall 2016. Weed densities were measured in Spring 2017 and volumetric soil moisture near the soil surface (5.1 cm depth) was measured at time intervals beginning in December 2016 and ending in March 2017. With the exception of ‘UC937’, barley varieties caused marked reductions in weed density in comparison with the unplanted control. Soil moisture content for the unplanted control was consistently lower than soil moisture contents for barley plots. Barley variety did not influence volumetric soil moisture. During the 2017–2018 growing season, we re-examined three barley varieties considered most amenable to the cropping system requirements (‘Robust’, ‘UC603’, ‘P919’), and these varieties were again found to support few weeds (≤ 5.0 weeds m ⁻² ). We conclude that several organically certified barley varieties could fill the need for a ‘non-thirsty’ cover crop that suppresses winter weeds in irrigated organic systems in the southwestern United States.
