A Decade of Progress in Organic Cover Crop-Based Reduced Tillage Practices in the Upper Midwestern USA
A Decade of Progress in Organic Cover Crop-Based Reduced Tillage Practices in the Upper...
Silva, Erin M.;Delate, Kathleen
agriculture Article A Decade of Progress in Organic Cover Crop-Based Reduced Tillage Practices in the Upper Midwestern USA 1 , 2 Erin M. Silva * and Kathleen Delate Department of Plant Pathology, University of Wisconsin-Madison, 1630 Linden Dr., Madison, WI 53706, USA Departments of Agronomy and Horticulture, Iowa State University, 106 Horticulture Hall, Ames, IA 50011, USA; firstname.lastname@example.org * Correspondence: email@example.com; Tel.: +1-608-890-1503; Fax: +1-608-263-2626 Academic Editor: Patrick Carr Received: 6 March 2017; Accepted: 3 May 2017; Published: 7 May 2017 Abstract: The organic industry continues to expand in the United States (U.S.), with 14,093 organic farms in 2014. The upper Midwestern U.S. has emerged as a hub for organic row crop production; however, the management of these organic row crop hectares heavily relies on tillage and cultivation for weed control. Faced with the soil quality challenges related to these practices, and cognizant of the beneﬁts of conventional no-till practices, organic farmers have shown signiﬁcant interest in the development of Cover Crop-Based Reduced Tillage (CCBRT) techniques to lessen soil disturbance while achieving successful weed management. To serve this farmer interest, signiﬁcant research efforts have been conducted in the upper Midwestern U.S., focused on systems-based practices to ensure adequate suppression of weeds, through a combination of agronomic and cover crop species and variety selection. Within this review article, we discuss the agronomic successes that have been achieved in CCBRT using a combination of cereal rye and soybeans, resulting in consistent suppression of weeds while providing fuel and labor savings for farmers, as well as the continued challenges that have persisted with its implementation. Continued investment in research focused on cover crop breeding and management, optimization of CCBRT equipment and fertility management, and a greater understanding of rotation effects will contribute to the further expansion of this technique across organic farms. Keywords: organic agriculture; cover cropping; reduced tillage; ecosystem services; USA 1. Introduction The organic industry continues to expand in the United States (U.S.), with 14,093 certiﬁed organic farms in 2014 [1–3]. The 2014 National Agricultural Survey of organic production, conducted by the United States Department of Agriculture (USDA), reported 82,328 hectares of organic corn and 39,996 hectares of organic soybean among the 1.4 million organic cropland and vegetable hectares in the U.S. . Management of these organic row crops heavily relies on tillage and cultivation for weed control. While mechanical practices can be effective to manage weeds, these activities prevent organic farmers from fully optimizing the requirement for soil building, as set forth in 7 CFR §205.203 and 205.205 of the National Organic Program (NOP) . In typical organic row crop production in the upper Midwestern U.S., ﬁve to six tractor passes with tine weeders, rotary hoes, and/or row cultivators are often necessary for adequate weed control, which can negatively impact soil aggregation and soil organic matter concentrations, while exposing the land to greater risk of erosion. Additionally, the reliance on cultivation as a primary weed management tool poses risks during wet springs, an Agriculture 2017, 7, 44; doi:10.3390/agriculture7050044 www.mdpi.com/journal/agriculture Agriculture 2017, 7, 44 2 of 13 increasingly common production challenge with heavy rainfalls occurring more frequently as a result of climate change ; consistently wet soil conditions can prevent organic producers from implementing timely weed management through cultivation, increasing weed competition and weed seedbanks while negatively impacting yields. Ongoing data from the Wisconsin Integrated Cropping Systems Trial, a long-term management trial begun in 1989, illustrates that while organic management results in comparable yields to conventional management during more moderate production seasons, years Agriculture 2017, 7, 44 2 of 14 exhibiting wet spring conditions result in yields of corn and soybeans falling to approximately 75% of those produced using conventional practices, due to the inability of farmers to conduct timely weed increasingly common production challenge with heavy rainfalls occurring more frequently as a result of climate change ; consistently wet soil conditions can prevent organic producers from management . implementing timely weed management through cultivation, increasing weed competition and weed In addition to weed management challenges associated with tillage and cultivation, these practices seedbanks while negatively impacting yields. Ongoing data from the Wisconsin Integrated Cropping can also increase the risk for soil erosion. Several Midwestern regions of the U.S. which support high Systems Trial, a long‐term management trial begun in 1989, illustrates that while organic concentrations of organic farms, including the Driftless regions of Wisconsin, Iowa, and Minnesota, management results in comparable yields to conventional management during more moderate production seasons, years exhibiting wet spring conditions result in yields of corn and soybeans are characterized by farm ﬁelds exceeding 4% or greater slopes. The soils in these regions vary widely, falling to approximately 75% of those produced using conventional practices, due to the inability of from heavy, poorly drained clay soils to sandy, shallow, droughty soils. These conditions create a farmers to conduct timely weed management . landscape susceptible to erosion, negatively impacting both soil and water quality of several key In addition to weed management challenges associated with tillage and cultivation, these watersheds, including the Mississippi Valley Watershed. practices can also increase the risk for soil erosion. Several Midwestern regions of the U.S. which support high concentrations of organic farms, including the Driftless regions of Wisconsin, Iowa, and Conventional no-till farming techniques have been promoted for their role in reducing water Minnesota, are characterized by farm fields exceeding 4% or greater slopes. The soils in these regions runoff and soil erosion, as well as maintaining soil carbon [7,8], although the degree and nature to vary widely, from heavy, poorly drained clay soils to sandy, shallow, droughty soils. These which the conventional no-till systems build soil C, and the degree to which this C is stably stored, can conditions create a landscape susceptible to erosion, negatively impacting both soil and water quality vary [9,10]. No-till systems can also increase inﬁltration of water into the soil by 25 to 50% compared of several key watersheds, including the Mississippi Valley Watershed. Conventional no‐till farming techniques have been promoted for their role in reducing water with conventional tillage systems . In addition, cover crop surface residues can decrease the effect runoff and soil erosion, as well as maintaining soil carbon [7,8], although the degree and nature to of wind and temperature on soil water evaporation, increase water storage in the soil proﬁle [12,13], which the conventional no‐till systems build soil C, and the degree to which this C is stably stored, scavenge available nitrogen, and prevent soil erosion , thus preventing watershed contamination can vary [9,10]. No‐till systems can also increase infiltration of water into the soil by 25 to 50% and nutrient losses [14,15]. compared with conventional tillage systems . In addition, cover crop surface residues can decrease the effect of wind and temperature on soil water evaporation, increase water storage in the Faced with the soil quality challenges associated with tillage and cultivation, and cognizant of soil profile [12,13], scavenge available nitrogen, and prevent soil erosion , thus preventing the beneﬁts of conventional no-till practices, organic farmers have shown signiﬁcant interest in the watershed contamination and nutrient losses [14,15]. development of no- and reduced-tillage techniques suitable for organic production. Within the majority Faced with the soil quality challenges associated with tillage and cultivation, and cognizant of of the reduced tillage systems currently utilized by organic farmers, no-till phases are incorporated the benefits of conventional no‐till practices, organic farmers have shown significant interest in the development of no‐ and reduced‐tillage techniques suitable for organic production. Within the throughout the rotation, with tillage limited to establishing the cover crops [16–18]. This technique, majority of the reduced tillage systems currently utilized by organic farmers, no‐till phases are often referred to as Cover Crop-Based Reduced Tillage (CCBRT) uses mature cover crop residue as incorporated throughout the rotation, with tillage limited to establishing the cover crops [16–18]. This a mulch to smother weeds, replacing the standard organic weed management tactics of tillage and technique, often referred to as Cover Crop‐Based Reduced Tillage (CCBRT) uses mature cover crop cultivation. Winter annual cover crops (typically cereal rye (Secale cereale L.) and hairy vetch (Vicia villosa residue as a mulch to smother weeds, replacing the standard organic weed management tactics of tillage and cultivation. Winter annual cover crops (typically cereal rye (Secale cereale L.) and hairy L.)) are seeded in the fall and terminated mechanically without herbicides in the spring, often using a vetch (Vicia villosa L.)) are seeded in the fall and terminated mechanically without herbicides in the roller-crimper (Figure 1a) which creates an in situ surface mulch that physically suppresses weeds. spring, often using a roller‐crimper (Figure 1a) which creates an in situ surface mulch that physically At the time of cover crop termination, the cash crop (typically soybean (Glyine max (L.) Merr.) or suppresses weeds. At the time of cover crop termination, the cash crop (typically soybean (Glyine max ﬁeld corn (Zea mays L.)) is planted directly into the cover crop mulch (Figure 1b), which provides (L.) Merr.) or field corn (Zea mays L.)) is planted directly into the cover crop mulch (Figure 1b), which provides season‐long weed suppression without further soil disturbance throughout cash crop season-long weed suppression without further soil disturbance throughout cash crop production. production. (a) (b) Figure 1. (a) Photograph of the roller‐crimper design commonly used by farmers and researchers in Figure 1. (a) Photograph of the roller-crimper design commonly used by farmers and researchers in the upper Midwestern U.S.; (b) Photograph of soybeans emerging through the rolled winter cereal the upper Midwestern U.S.; (b) Photograph of soybeans emerging through the rolled winter cereal rye mulch. rye mulch. Agriculture 2017, 7, 44 3 of 13 2. Organic Cover Crop-Based Reduced Tillage in the Upper Midwestern U.S. The upper Midwestern U.S. maintains a long history in organic farming, and still remains a primary center of the U.S. organic industry . Prior to the rise of organic agriculture, regional environmental leaders, such as Aldo Leopold, an ardent environmentalist, and Gaylord Nelson, a Wisconsin politician, inspired a strong land ethic in upper Midwestern culture. Counter to the argument that the maturation of the organic industry will, by default, lead to a concurrent conventionalization of the industry, the production practices used by upper Midwestern organic farmers demonstrate adherence to the soil-building ethic that serves as a foundation of the organic regulation outlined by the NOP . CCBRT research began in the early 2000s in the upper Midwest, with several research programs, including Iowa, Wisconsin, and Michigan, establishing experimental plots both at land-grant university research stations and on working certiﬁed organic farms. Research approaches have predominantly centered on techniques and equipment made popular by the Rodale Institute in Kutztown, PA, where a fall-planted cover crop is mechanically terminated in the spring (cereal grains at anthesis at Zadok’s growth stage 60, or legumes at 100% bloom). Cover crop termination is achieved with a roller-crimper, a hollow steel cylinder with metal slats arranged in a chevron pattern, welded at uniform spacing along the length of the drum that can be ﬁlled with water for added weight [20–22] (Figure 1a). However, research programs have also included cover crop termination treatments that utilize sickle-bar mowing and ﬂail mowing [20,22]. Much of the CCBRT research in the upper Midwestern U.S. has focused on systems-based practices to ensure effective suppression of weeds, primarily through a combination of agronomic practices and cover crop management. Corn and soybean have been the primary commodity crops that have been evaluated within the CCBRT system in this region. However, studies have also addressed other critical aspects of the system, including cash crop yields, economic assessments regarding fuel and labor savings, and reduction in erosion risk. As research data is generated and practical experiences are reported by organic farmers, CCBRT has also been not only gaining recognition, but is being implemented across the organic agricultural landscape. According to the 2014 USDA Organic Survey, organic farmers in the upper Midwest are increasingly adopting organic no-till management strategies as part of their farming practices. Of the 3319 certified organic farms in of Iowa, Illinois, Michigan, Minnesota, Missouri, Nebraska, and Wisconsin, 957 reported the use of no-till practices . This survey, however, does not provide adequate resolution to determine whether CCBRT practices in row crops are being used, or whether other no-till practices are being reported, such as reseeding grasses and legumes into existing pastures without tillage. On a state level, the reported use of no-till practices ranged from 20 to 37% of organic farms (Iowa: 27% (166 no-till farms, 612 total organic farms); Illinois: 27% (69, 249); Michigan: 20% (67, 332); Minnesota; 37% (189, 512); Missouri: 28% (61, 216); Nebraska: 32% (54, 170); Wisconsin: 29% (351, 1228)) . The remainder of this paper summarizes experiences with CCBRT in the upper Midwestern U.S., incorporating published results from research studies and on-farm observations. Several platforms exist from which data and information are assembled: (1) land grant University research programs, particularly the efforts in Wisconsin and Iowa; and (2) organic farmer networks and participatory research efforts, such as OGRAIN (the Organic Grain Resource and Information Network), led by the University of Wisconsin-Madison. Further, the authors discuss remaining barriers in the CCBRT system which prevent more wide scale adoption in the upper Midwestern US, and further research needs necessary to address those barriers. 3. Summary of CCBRT Research in the Upper Midwestern U.S. 3.1. Organic Soybean Production Weed management in organic cropping systems remains a signiﬁcant challenge for organic farmers, particularly in the soybean phase of a typical corn–soybean-winter wheat–alfalfa rotation Agriculture 2017, 7, 44 4 of 13 common to organic grain systems in the upper Midwestern U.S. [21,22]. Unlike corn and winter wheat, which develop above-ground biomass early in the growing season and thus more effectively compete with weeds, soybean crops, often planted on the wider row spacing for cultivation, can be relatively slow to canopy, allowing weeds to establish over a prolonged period during the ﬁrst half of the production season. As such, the development of CCBRT techniques for this phase of the crop rotation to augment mechanical weed management strategies during soybean production addresses a critical production challenge. CCBRT research in organic soybean production in the upper Midwestern U.S. have integrated the establishment of a cereal grain cover crop (most often cereal rye) in late summer or early fall, typically seeding at a rate of 180–269 kgha [20,22] (Table 1). The cereal grain cover crop is then terminated in late spring, with soybean directly seeded through the cereal grain mulch, at rates of 500,000 seedsha ; or more. Other cereal grain cover crops have also been trialed for use in CCBRT, including Winter triticale (Tritocosecale Wittm. Ex A Camus), winter barley (Hordeum vulgare L.), ‘McGregor ’, and winter wheat (Triticum aestivum) [21,22]. While CCBRT has demonstrated its ability to effectively suppress weeds in organic soybean production [20,22], the capacity of the cover crop residue to prevent weeds from establishing varies widely depending on the weed species present in the ﬁeld. Small-seeded annual broadleaf weeds tend to be suppressed more easily by the mulch and thus are more dominant in tilled organic systems [23–25]; if ﬁelds have adequate mulch biomass and complete cover crop termination, up to 80% control of common annual weeds in winter rye stands have been reported . Perennial weeds are less sensitive to suppression by the mulch and readily proliferate in the system over time [25,27]. Weed management using the CCBRT technique is comprised of diversiﬁed approaches, with efﬁcacy driven by rye biomass levels, cash crop planting date, seeding rate and placement, and cash crop stand establishment. Under typical cropping conditions, rye can produce biomass levels that range from 4000 11,000 kgha  (Table 1). Research has demonstrated that in order to reliably suppress weeds as a surface mulch, the fall-planted cereal grain cover crop must reach biomass levels at the higher end of this range, ideally exceeding 8000 kgha [26,28]. This allows the mulch to effectively limit weed populations by not only physically interfering with the emergence process, but also preventing the breaking of seed dormancy and inhibiting weed germination through allelopathy . While CCBRT systems can produce soybean yields that are within state averages for organic soybeans, yields continue to lag behind organic systems that are managed using typical tillage practices. Research in Iowa and Wisconsin has demonstrated that, while during some seasons CCBRT yields are not signiﬁcantly different than typically managed organic soybean, in many circumstances yield reductions in CCBRT systems as compared to typical organic soybean yields are observed, even with planting dates remaining the same, with up to a 24% or more reduction in yields observed [20,21]. Reasons for these observed yield reductions may be multi-fold: (1) cooler soil temperatures under the rye residue delaying soybean germination; (2) slower or inhibited root growth under the rye mulch; (3) nutrient tie-up under the rye mulch; and (4) allelopathic effects of the cereal rye. Whereas soybean biomass at the end of the production season is similar between CCBRT and typically managed organic soybean, early season growth of CCBRT soybeans has been observed to be slower as compared to typical organic production practices. As the weed pressure experienced within the two systems has been observed to be either equivalent or less in the CCBRT, it is unlikely that weed competition is a primary factor resulting in the observed yield differences. Agriculture 2017, 7, 44 5 of 13 Table 1. Summary of results of Cover Crop-Based Reduced Tillage (CCBRT) research conducted in the upper Midwestern U.S.A. as reported in peer-reviewed research journals. Cover Cover Cover Crop Cash Crop Seeding Cash Crop Weed Cash Crop Cover Crop Crop Crop Soybean Study Location Cover Crop Variety Seeding Rate and Rate and Row Planting Populations/ Stand Citation Planting Date Termination Biomass at Yields Row Spacing Spacing Date Biomass Populations Date Termination Soybean ((Glycine max (L.) Merr.)) Cereal rye (Secale cereale 72 kgha cereal Zadoks L.), Variety Not Speciﬁed 12 September 494,210 seedsha ; 7–8 226,719–308,733 1067–2724 1 2 Iowa rye, 36 kgha growth N/A 23–25 May  2 1 1 (VNS)/VNS hairy vetch and 31 October 76 cm rows weedsm plantsha kgha hairy vetch stage 60 (Vicia villosa L.) Winter wheat (Triticum aestivum L.) (‘Expedition’ Zadoks 63 kgha winter 12 September 9–15 209,422–275,357 628–5668 494,210 seedsha ; and ‘Arapahoe’/winter growth N/A 23–25 May  wheat, 21 kgha 2 1 1 and 31 October weedsm plantsha kgha 76 cm rows pea (Pisum sativum subsp. stage 60 Winter Pea Arvense) cover crop) 4.3–10.8 1 1 5 October and 7 180 kgha , 19 cm 625,200 seedsha ; 377,100–505,600 2751–2885 Wisconsin Cereal rye, ‘Rymin’ 6–11 June Mg 18–21 May 3–229 kgha  1 1 October row spacing 19 cm row spacing plantsha kgha DMha 8 September and 33.6 kgha , 19 28 May–8 3.7–5.0 4–47 Hairy vetch, ‘VNS’ N/A N/A N/A N/A  1 2 13 September cm row spacing June MgDMha weedsm 8 September and 28 May–8 10.2–10.3 1–25 269 kgha , 19 cm Winter rye, ‘VNS’ N/A N/A N/A N/A  1 2 13 September June MgDMha weedsm row spacing Winter triticale 8 September and 269 kgha , 19 cm 28 May–8 6.4–14.6 24–26 (Tritocosecale Wittm. Ex A N/A N/A N/A N/A  1 2 13 September row spacing June MgDMha weedsm Camus), ‘Fridge’ Austrian winter pea 8 September and 44.6 kgha , 19 28 May–8 0–6.3 0–18 (Pisum sativum subsp. N/A N/A N/A N/A  1 2 13 September cm row spacing June MgDMha weedsm arvense), ‘VNS’ Winter barley (Hordeum 8 September and 269 kgha , 19 cm 28 May–8 10.3–11.7 19–43 N/A N/A N/A N/A  1 2 vulgare L.), ‘McGregor ’ 13 September row spacing June MgDMha weedsm Corn (Zea mays L.) Cereal rye (Secale cereale Zadoks 72 kgha cereal L.), Variety Not Speciﬁed 12 September 45,302–59,510 628–5668 79,073 seedsha ; Iowa growth N/A 23–25 May N/A  rye, 36 kgha 1 1 (VNS)/VNS hairy vetch and 31 October plantsha kgha 76 m rows stage 60 hairy vetch (Vicia villosa L.) Winter wheat (Triticum aestivum L.) (‘Expedition’ 63 kgha winter Zadoks 12 September 79,073 seedsha ; 49,824–51,479 640–5567 and ‘Arapahoe’/winter wheat, 21 kgha growth N/A 23–25 May N/A  1 1 and 31 October 76 cm rows plantsha kgha pea (Pisum sativum subsp. winter pea stage 60 Arvense) cover crop) 1 2 Ranges of values in a given column reﬂect data from separate years in a given study, due to signiﬁcant year effects N/A: designates data not included in publication. Agriculture 2017, 7, 44 6 of 13 3.2. Organic Corn Production Experimentation with CCBRT in the corn phase of the crop rotation has primarily differed with respect to the cover crop used in the system. Whereas the same planting strategies are used—a winter-hardy cover crop is seeded in the late summer and terminated during the following spring—CCBRT techniques for corn have integrated the leguminous cover crops, occasionally in combination with a cereal grain to enhance mulch biomass [21,22] Hairy vetch (Vicia villosa L.) has been the most commonly researched and trialed legume cover crop in the corn CCBRT system, although alternative legumes such as Austrian winter pea and ﬁeld pea (Pisum sativum subsp. arvense) have also been tested [21,22]. Seeding dates of these legume cover crops have been similar to those used in the establishment of cereal grain cover crops (late summer/early fall), with seeding rates ranging from 33.6–44.6 kgha . As with the effective mechanical termination of cereal grain cover crops, legume cover crops must be terminated at speciﬁc maturities. To obtain effective termination, roller-crimping or mowing must occur at 100% bloom to early pod set [29,30]. In the upper Midwest, this growth stage varies from late May (Austrian winter pea) to mid-June (hairy vetch) . While a late May planting date can allow for corn grain and silage production. If appropriate short-season varieties of corn are used, mid-June planting dates substantially decrease the yield potential of organic corn, for both silage and grain. Within the Austrian winter pea cultivars that are commercially available, winter-hardiness remains marginal in the region, thus reducing the feasibility of this cover crop into the CCBRT system. With hairy vetch remaining the only reliable option for an overwintering legume cover crop which produces adequate biomass for an effective weed-suppressive mulch, CCBRT organic corn systems remain challenging if not prohibitive. CCBRT in the corn phase has also proven more challenging than soybean due to increased risk of insect pest interactions. In research trials at the University of Wisconsin Arlington Agricultural research station, CCBRT corn stands have been decimated by army worm (Mythimna unipuncta Haworth), particularly when cover crop stands have included a cereal grain. This insect pest, which oviposits on the lower leaves of grasses or the base on grass plants, can be attracted to the cereal grain cover crop during its migration from the southern states of the U.S. Depending on the timing of this migration, newly hatched larvae may emerge from the cover crop residue at the time of corn germination, then feeding upon the corn seedlings. Although it has not been observed, depending on annual conditions and insect life cycles, a similar risk exists with seed corn maggot (Delia platura Meigen), a common corn insect pest. which lays eggs on decaying vegetation in late April or early May. Without the option to use chemical insecticide seed treatments, the development of CCBRT strategies must account for ecological-based management solutions, such as avoiding the use of cover crops that are preferred hosts to insect pests and the altering of cash crop planting dates to avoid speciﬁc pest cycles, to mitigate the risk of insect damage to the cash crop. 3.3. Economics and Labor/Fuel Savings Several CCBRT studies conducted in the upper Midwestern U.S. have integrated economic analyses into their data analysis (Table 2). In an analysis conducted by Bernstein et al. , returns to labor, capital, and management of the CCBRT treatments using cereal rye were 27% less than in the organic tilled system, primarily due to the 24% yield reduction shown in this particular study. However, the study also documented that labor and fuel inputs were reduced by nearly 50% in the no-till cereal rye treatments. Although the proﬁtability per hectare was greater in the tilled treatment, the return per labor hour was 25% greater in the no-till cereal rye system. These savings not only translate to economic savings, but could have positive impacts on the farmers’ quality of life, potentially allowing them to engage in other enterprises or expand their soybean acres. Signiﬁcant diesel fuel savings were also documented, with 720 L of diesel fuel saved using no-till techniques. Delate et al.  found similar results, with signiﬁcantly less labor costs in the CCBRT systems. As with the Bernstein study, Agriculture 2017, 7, 44 7 of 13 returns to land and management remained less in the CCBRT systems as compared to the typical organic management systems, due to persistent soybean yield reductions. Table 2. Economic analyses of CCBRT systems in the upper Midwestern U.S. Cash Crop Gross Return to Study Yields Cash Crop Cover Crop Row Revenue Management Citation Location kgha 1 1 Spacing USDha USDha 1067–2724 Iowa Soybean Cereal rye/hairy vetch 76 cm 672–1769 63–993  Winter wheat/winter pea 1042–2862 656–1859 36–1198 No cover crop 2197–3170 1383–2059 742–1377 (traditional tillage) Corn Cereal rye/hairy vetch 76 cm 628–5668 217–1394 660–527 Winter wheat/winter pea 640–5567 221–1369 540–618 No cover crop 7777–9710 2389–2694 1602–1866 (traditional tillage) Wisconsin Soybean Cereal rye 19 cm 2751–2885 N/A 1598–1687  No cover crop 76 cm 3618 2162 (traditional tillage) Ranges of values in a given column reﬂect data from separate years in a given study, due to signiﬁcant year effects. N/A: designates data not included in publication. The CCBRT studies focused on organic corn are much more limited. Delate et al. , over two years of investigating CCBRT strategies using hairy vetch/rye and winter wheat/winter pea, found return to management to range from an economic loss ( 660 USDha ) to more proﬁtable scenarios (618 USDha ) (Table 2). In both years over both production systems, however, return to management was signiﬁcantly less than the tilled organic corn systems (1602–1866 USDha ). 3.4. Impact of CCBRT on Soil Quality Parameters The adoption of reduced-tillage practices such as CCBRT has been promoted as a tool to mitigate soil C loss, build soil organic matter (SOM), and reduce the risk of erosion . However, in large part due to the lack of long-term organic CCBRT experimental sites, the impact of CCBRT techniques on increasing soil C and SOM remains unclear. Clark et al. (2017) , investigating the impact of CCBRT techniques on soil parameters in organic row crop production in Missouri, USA, reported no change in soil organic carbon (SOC) under CCBRT management, but concluded this may be due to the short two-year time frame of the experiment. Using the Revised Universal Soil Loss Equation, Version 2 to predict soil loss, Bernstein et al.  estimated that the CCBRT soybean plots integrating cereal rye as a 1 1 cover crop would result in a soil loss of 1.5 Mgha on a 1.0% slope and 5.6 Mgha on a 4.5% slope, signiﬁcantly less than the predicted soil loss on the organic till soybean ﬁelds, which ranged from 1 1 10.9 Mgha on a 1.0% slope to 49.3 Mgha on a 4.5% slope. While not measured directly, these same models predicted changes in soil organic matter (soil conditioning index, on a scale of 2 to +2), were positive in CCBRT rye treatments (+0.4 on 1.0% slope and +0.3 on 4.5% slope) and negative in the tilled rye treatment for both slope grades, ( 0.9 on 1.0% slope and >