Cover crop adoption is increasing among growers with the occurrence of herbicide-resistant weed species. A field study conducted at three sites from autumn 2021 through the crop harvest in 2022 in Alabama aimed to evaluate the combined effect of cover crop residue and herbicides for weed control and improved cotton lint yield. The experiment was conducted in split-plot design with main plots consisting of six cover crop treatments: cereal rye, crimson clover, oat, radish, cover crop mixture, and winter fallow. The subplots included four herbicide treatments: (i) preemergence, pendimethalin + fomesafen, (ii) postemergence, dicamba + glyphosate + S-metolachlor, (iii) preemergence followed by postemergence, and (iv) nontreated (NT) check. Cover crops, excluding radish, exhibited greater weed biomass reduction than winter fallow with corresponding herbicide treatments of either preemergence, postemergence, or preemergence + postemergence as compared to control (winter fallow and NT check). Considering preemergence + postemergence treatment, cereal rye, crimson clover, oat, and cover crop mixture provided >95% weed biomass reduction as compared to control. Looking at the overall effect of cover crop, cereal rye outperformed and showed greater weed biomass reduction than radish relative to control. Preemergence + postemergence herbicide treatment resulted in greater lint yield than other treatments. Cotton in cereal rye plots had a greater lint yield than in winter fallow at one out of three locations. In conclusion, integrating herbicides and incorporating high-residue cover crops such as cereal rye is an effective weed management strategy to control troublesome weeds.

Two separate field experiments were conducted during the 2021-22 and 2022-23 growing seasons at Kansas State University Agricultural Research Center near Hays, KS to understand the emergence dynamics of glyphosate-resistant (GR) kochia [Bassia scoparia (L.) A. J. Scott] as influenced by fall- and spring-planted cover crops (CC) and residual herbicide. Study sites were under winter wheat (Triticum aestivum L.)-sorghum [Sorghum bicolor (L.) Moench]-fallow rotation with a natural seedbank of GR B. scoparia. In experiment 1, fall-planted CC mixture (triticale/winter peas/radish/rapeseed) was planted after wheat harvest and terminated at triticale [xTriticosecale Wittm. Ex A. Camus [Secale x Triticum] heading stage (next spring before sorghum planting). In experiment 2, spring-planted CC mixture (oats/barley/spring peas) was planted in sorghum stubbles and terminated at oats (Avena sativa L.) heading stage. Four treatments were established in each experiment: (1) nontreated control (no CC and no herbicide), (2) chemical fallow (no CC but glyphosate + acetochlor/atrazine or flumioxazin/pyroxasulfone + dicamba were used to control weeds), (3) CC terminated with glyphosate, and (4) CC terminated with glyphosate plus residual herbicide (acetochlor/atrazine for fall-planted CC and flumioxazin/pyroxasulfone for spring-planted CC). Results indicated that fall-planted CC delayed GR B. scoparia emergence by 3 to 5 weeks whereas spring-planted CC delayed emergence by 0 to 2 weeks compared to nontreated. Fall-planted CC terminated with glyphosate plus acetochlor/atrazine reduced the cumulative emergence of GR B. scoparia by 90 to 95% compared to nontreated across both yrs. Similarly, spring-planted CC terminated with glyphosate plus flumioxazin/pyroxasulfone reduced the cumulative emergence of GR B. scoparia by 83 to 90% compared to nontreated. These results suggest that fall- or spring-planted CC in combination with residual herbicide at termination can be utilized for GR B. scoparia suppression. Results from this study will help in developing prediction models for GR B. scoparia emergence under different CC strategies.

Integrated weed management practices that reduce selection for resistance on herbicides are critical to delay resistance. To quantify the reduction in selection for resistance placed on Palmer amaranth from 2,4-D applied postemergence in cotton, an experiment was conducted three times in Georgia during 2020 and 2021 evaluating the benefits of (i) a cover crop, (ii) preemergence herbicides, and (iii) timeliness of applications. When a timely total-postemergence program of glyphosate + 2,4-D was applied three times over the season in a conventionally tilled system, 281,690 glyphosate-resistant Palmer amaranth plants ha–1 were exposed to 2,4-D. Over 61,500 of these plants were exposed to multiple 2,4-D applications. Altering the production system to conservation tillage, and including a rolled-rye cover crop, reduced the total number of plants exposed to 2,4-D for the season by 72% and the number of plants exposed multiple times by 60%. Even more effective, including a mixture of residual preemergence herbicides reduced the number of plants exposed to 2,4-D at least once over 99.9%, and reduced multiple exposures over 99.3% for the season; this benefit was observed for both conventional and conservation tillage systems. Delaying the initial application of the total-postemergence program did not influence the number of Palmer amaranth plants treated at least once but increased the number of plants treated multiple times by a factor of 3.7 times. As a result of early-season weed competition, cotton height and yield reductions were also associated with both lack of preemergence residuals and delayed postemergence applications. When considering the goal of minimizing the number of Palmer amaranth treated with a postemergence application of 2,4-D in a cotton system, the preemergence was the most effective option followed by (fb) the cover crop fb making timely postemergence applications. However, the most effective approach was to utilize each of these tactics in the same growing season.

Cover crop residue retention on the soil surface can suppress weeds and improve organic no-till soybean (Glycine max) yield and profitability compared to a tilled system. Appropriate cereal rye (Secale cereale) fall planting date and termination methods in the spring are critical to achieve these benefits. A plot-scale agronomic experiment was carried out from September 2018 to October 2021 in Kutztown, PA, USA to demonstrate the influence of cereal rye planting date (September or October) and mechanical termination method [no-till (I & J roller-crimper, Dawn ZRX roller, and mow-ted) and tilled (plow-cultivate)] on cover crop regrowth density, weed biomass, soybean yield, and economic returns. In one out of three years, the September rye planting accumulated more cover crop biomass than the October planting, but the regrowth of the rye after roller-crimping was greater with this planting date. Cover crop planting date had no effect on total weed biomass and demonstrated varying effects on soybean grain yield and economic returns. The Dawn ZRX roller outperformed the I & J roller-crimper in effectively terminating cover crops, while the I & J roller-crimper demonstrated more uniform weed suppression and led to greater soybean yields over a span of three years. Organic no-till strategies eliminated the need for tillage and reduced variable costs by 14% over plow-cultivated plots, and generated ~19% greater net revenue across the study period (no-till vs tillage = US $845 vs US $711 ha−1). Terminating cereal rye with roller-crimping technology can be a positive investment in an organic soybean production system.

Palmer amaranth (Amaranthus palmeri S. Watson) is the most problematic weed of cotton (Gossypium hirsutum L.)-cropping systems in the U.S. Southeast. Heavy reliance on herbicides has selected for resistance to multiple herbicide mechanisms of action. Effective management of this weed may require the integration of cultural practices that limit germination, establishment, and growth. Cover crops have been promoted as a cultural practice that targets these processes. We conducted a 2-yr study in Georgia, USA, to measure the effects of two annual cover crops (cereal rye [Secale cereale L.] and crimson clover [Trifolium incarnatum L.]), a perennial living mulch (‘Durana®’ white clover [Trifolium repens L.]), and a bare ground control on A. palmeri population dynamics. The study was conducted in the absence of herbicides. Growth stages were integrated into a basic demographic model to evaluate differences in population trajectories. Cereal rye and living mulch treatments suppressed weed seedling recruitment (seedlings seed−1) 19.2 and 13 times and 12 and 25 times more than the bare ground control, respectively. Low recruitment was correlated positively with low light transmission (photosynthetic active radiation: above canopy photosynthetically active radiation [PAR]/below cover crop PAR) at the soil surface. Low recruitment rates were also negatively correlated with high survival rates. Greater survival rates and reduced adult plant densities resulted in greater biomass (g plant−1) and fecundity (seeds plant−1) in cereal rye and living mulch treatments in both years. The annual rate of population change (seeds seed−1) was equivalent across all treatments in the first year but was greater in the living mulch treatment in the second year. Our results highlight the potential of annual cover crops and living mulches for suppressing A. palmeri seedling recruitment and would be valuable tools as part of an integrated weed management strategy.

Unproven economic returns at the farm level are a major barrier to large-scale adoption of cover crops. The objective of this study was to evaluate the short-run private net returns to producers implementing a cereal rye (Secale cereale L.) cover crop preceding the no-till corn (Zea mays L.) phase of a US Midwest corn–soybean (Glycine max [L.] Merr.) rotation in an integrated crop and cow–calf operation. We used experimental agronomic data from six location-years in Iowa to estimate private net returns to cereal rye across alternative scenarios in a partial budget framework. Net returns in the absence of grazing averaged −$123.74 ha−1 and were negative for 82.2% of the treatments, while net returns under partial grazing averaged −$15.24 ha−1 and were negative for 54.8% of the treatments. Early-broadcast cereal rye produced higher biomass and larger net cost savings in the livestock enterprise than late-drilled cereal rye, but it also resulted in higher corn yield penalties. In the no-grazing scenario, net losses for early-broadcast cereal rye were $165.97 ha−1 larger, on average, than for late-drilled cereal rye. Our findings should raise awareness about the low probability of obtaining positive annual private net returns to cereal rye in Iowa in the absence of sizable targeted financial incentives, and inform the policy discussion on the cost-effectiveness of government-sponsored conservation programs.

Herbicides are often used to terminate cover crops. Producers would like to use herbicides that work quickly, are effective, and do not increase the risk of selecting herbicide-resistant weeds. Eight experiments were conducted to determine whether mixing glyphosate (900 g a.e. ha−1) with rimsulfuron (15 g a.i. ha−1), mesotrione (100 g a.i. ha−1), or rimsulfuron + mesotrione enhances winter rye control and to ascertain whether using urea ammonium nitrate (UAN) as the herbicide carrier improves and accelerates herbicide efficacy. Winter rye control was assessed 1, 2, 3, and 4 wk after application (WAA) and biomass was measured 4 WAA. The addition of rimsulfuron, mesotrione, or rimsulfuron + mesotrione to glyphosate did not enhance winter rye control. Similarly, using UAN as the herbicide carrier did not improve or accelerate herbicide efficacy. Glyphosate alone provided the greatest level of winter rye control. The addition of rimsulfuron, mesotrione, or rimsulfuron + mesotrione to glyphosate did not increase the level or speed of control. However, mixing glyphosate with rimsulfuron, mesotrione, or rimsulfuron + mesotrione adds other modes of action without compromising winter rye control.

Granular temporal and spatial scale observations of conservation practices are essential for identifying changes in the production systems that improve soil health and water quality and inform long-term agricultural research and adaptive policy development. In this study, we demonstrate an innovative use of farmer practice survey data and what can be uniquely known from a detailed survey that targets specific farm groups with a regional focus over multiple consecutive years. Using three years of survey data (n = 3914 respondents), we describe prevailing crop rotation, tillage, and cover crop practice use in four Midwestern US states. Like national metrics, the results confirm dominant practices across the landscape, including corn-soybean rotation, little use of continuous no-till, and the limited use of cover crops. Our detailed regional survey further reveals differences by state for no-till and cover crop adoption rates that were not captured in federal datasets. For example, 66% of sampled acreage in the Midwest has corn and soybean rotation, with Illinois having the highest rate (72%) and Michigan the lowest (41%). In 2018, 20% of the corn acreage and 38% of the soybean acreage were in no-till, and 13% of the corn acres and 9% of the soybean acres were planted with a cover crop. Cover crop adoption rates fluctuate from year to year. Results demonstrate the value of a farmer survey at state scales over multiple years in complementing federal statistics and monitoring state and yearly differences in practice adoption. Agricultural policies and industry heavily depend on accurate and timely information that reflects spatial and temporal dynamics. We recommend building an agricultural information exchange and workforce that integrates diverse data sources with complementary strengths to provide a greater understanding of agricultural management practices that provide baseline data for prevailing practices.

Given the potential environmental and economic sustainability consequences of cover crop adoption, N fertilizer application, and residue management, this study focuses on the yield and financial effects of these on processing tomato production in Ontario, Canada. The study employs financial modeling using field data from a long-term cover crop experiment (oat, cereal rye, radish, and a radish-rye mixture) from 2010 to 2020. Averaged over six experimental years, compared to no cover (87 Mg ha−1) radish (99.6 Mg ha−1) and radish-rye mix (95.2 Mg ha−1) cover crops produce statistically significantly higher tomato yields as isolated practices, increasing farm net returns by $1120 ha−1 and $604 ha−1, respectively. When combined with N application, rye application additionally results in tomato yields statistically significantly higher than the base practice of no cover crop, zero N application and retained residue. Oat cover does not appear to have a statistically significant effect on tomato yields in this dataset. The application of N fertilizer results in statistically significantly higher tomato yield, increasing net returns by $882 ha−1, while residue management does not.

Growers have been experimenting with cover crop termination timings to maximize weed suppression and potentially reduce herbicide inputs in soybean [Glycine max (L.) Merr.]. A field study was replicated three times from 2018 through 2021 in South Charleston, OH, to evaluate different management strategies involving a cereal rye (Secale cereale L.) cover crop. The objectives were to determine the effects of cereal rye seeding rate (0, 50, and 100 kg ha−1), management program (preplant, postplant, and delayed), and soybean residual herbicide (flumioxazin + chlorimuron ethyl and no herbicide) on cover crop, weed, and soybean parameters. The preplant program consisted of cereal rye terminated 7 d before planting (DBP) + a postemergence application. The postplant program consisted of cereal rye terminated 7 d after planting (DAP) + a postemergence application. In the delayed program, saflufenacil was applied in April and cereal rye was terminated 21 DAP, and there was no postemergence application. Giant foxtail (Setaria faberi Herrm.) density was reduced by the presence of cereal rye, averaged over other factors, regardless of seeding rate. Cereal rye seeding rate did not affect giant ragweed (Ambrosia trifida L.) density. The delayed management program was generally associated with the lowest weed density, but weed density was often similar in the postplant program. Setaria faberi density was lower in treatments that included a residual herbicide. Residual soybean herbicide use did not affect density of A. trifida. Terminating cereal rye after soybean planting resulted in increased soybean yield in 2019 and reduced yield in 2020, compared with preplant rye termination. These data suggest that adjusting the cereal rye management program may have a greater effect on weed suppression than adjustments to seeding rate. Delaying termination of cereal rye can aid in the suppression of weeds, but a comprehensive herbicide program was necessary to provide adequate (>85%) weed control.

This study develops and uses a survey to gather information on demographics, production and management practices, and perceptions on using cover crops as a conservation practice from citrus growers and utilizes the double-bounded dichotomous choice contingent valuation method to measure their willingness to pay (WTP) for adopting cover crops in citrus production. The survey is conducted for citrus producers in Florida and Texas. The study finds that, on average, growers from Florida are willing to pay $509.48/acre per year for adopting cover crops. This is substantially less than the WTP for growers in Texas, who are willing to pay more than $1,000/acre per year for cover crops. The study analyzes the factors that have significant impacts on growers’ WTP for cover crops and discusses the heterogeneity in the grower perceptions on the benefits and drawbacks of using this conservation practice by state. Although using cover crops has not been a popular conservation practice in perennial fruit production systems, its potential to improve soil quality is particularly important for citrus production in Florida where soils are sandy and have low organic matter.

Drill-interseeding cover crops into standing corn (V3 to V5 growth stage) provides opportunities for increasing functional diversity in cropping systems by facilitating use of cover crop mixtures that include grass, legume, and brassica species. Designing herbicide-based weed control programs that negotiate tradeoffs between crop protection and environmental goals when interseeding mixtures remains a major challenge. The objective of this study was to use greenhouse-based dose-response assays to describe the relative sensitivity of 12 cover crop species that differ in traits, including taxonomic group and seed mass, to chloroacetamide (acetochlor, dimethenamid, S-metolachlor; Group 15 herbicides as categorized by the Weed Science Society of America) and pyrazole (pyroxasulfone; Group 15) herbicides. Nonlinear models were fit, and effective doses were estimated (ED50) to compare relative sensitivities of cover crop species to each herbicide. Brassica species (winter canola, Dwarf Essex rape, daikon radish) were less sensitive than small-seeded legumes (medium red clover, crimson clover) and grasses (annual ryegrass) in response to each chloroacetamide, but similar in response to pyroxasulfone. Austrian winter pea, a large-seeded legume, was less sensitive to each herbicide compared to other legumes (crimson clover, medium red clover, hairy vetch). Cereal rye and triticale were less sensitive to dimethenamid, S-metolachlor, and pyroxasulfone compared to annual ryegrass, but similar sensitivities were observed for acetochlor. These results suggest that relative differences in sensitivity to chloroacetamide and pyrazole herbicides could be exploited when designing cover crop mixtures for interseeding. It is imperative, however, to use these findings in conjunction with field-based observations of cover crop injury potential in interseeded systems.

The effects of the farming system (conventional-organic-abandoned) and soil management (native cover crop vs tillage) on vascular plant species were analyzed in sloping olive groves (>20%) in 20 different locations in Andalusia, SE Spain. The soil management techniques included Organic Tillage (OT), Organic Cover Crops (OC), Conventional Tillage (CT), Conventional Non-Tillage (CNT), Abandoned Cover Crops (AC) and Abandoned Woody (AW). Data for the vascular plant species were recorded through three line transects of 30 m with a bar perpendicularly touching every 1 m of the measuring tape. Environmental variables were also recorded at plot level to assess their influence. Dependent variables, such as species abundance, richness and diversity indexes were studied using univariate analysis (one-way ANOVA, Kruskal–Wallis test) while multivariate statistics (ANOSIM, SIMPER, DCA) were used for analyzing the data matrices. We found that the different combinations of farming system and soil management affect biological diversity in terms of individual abundance, plant cover, species richness and diversity, species and family composition. Life forms and species distribution patterns are also affected. The main environmental variables affecting the plant taxa were those related with soil and climate characteristics, slope, olive age and intensive land uses at landscape level, including the percentage of artificial surfaces. The lowest levels of biodiversity (e.g., species richness) were found in the tilled olive groves (CT = 8.1 sp. ± 2.2, OT = 10.0 sp. ± 5.4). Surprisingly, the organic tilled groves (OT) were very poor in species compared to those with native plant cover (OC = 27.9 sp. ± 3.0). The latter, however, showed similar species richness to the abandoned olive groves (AC = 21.2 sp. ± 3.7, AW = 27.2 sp. ± 3.0). Possible solutions for increasingly uncompetitive sloping olive groves include conversion to organic with native plant cover or abandonment for rewilding.

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.

Crops emit a variety of volatile organic compounds (VOCs) that serve as attractants or repellents for pests and their natural enemies. Crop rotations, off-farm chemical inputs, and mechanical and cultural tactics – collectively called cropping systems – alter soil nutrients, moisture content, and microbial communities, all of which have the potential to alter crop VOC emissions. Soil legacy effects of diversified cropping systems have been shown to enhance crop VOC emissions in greenhouse studies, but how they influence emissions under field conditions remains virtually unknown. To determine the effect of cropping systems on plant VOC emissions in the field, air samples were collected from the headspace of wheat (Triticum aestivum L. Judee) grown in simplified wheat-fallow rotations or diversified wheat-cover crop rotations where cover crops were terminated by grazing cattle. Across two growing seasons, wheat grown in rotation with fallow emitted greater amounts of Z-3-hexenyl acetate and β-ocimene, key attractants for wheat stem sawfly (Cephus cinctus Norton), a major pest of wheat. While overall VOC blends were relatively similar among cropping system during the first growing season, emissions varied substantially in the second year of this study where wheat grown in rotation with cover crops emitted substantially greater quantities of volatile compounds characteristic of abiotic stress. Below-average precipitation in the second growing season, in addition to reduced soil water content in cover crop rotations, suggests that cropping system effects on wheat VOCs may have been driven primarily by water availability, a major factor limiting crop growth in dryland agriculture. While the specific mechanisms driving changes in VOC emissions were not explicitly tested, this work shows that agricultural practices applied in one growing season can differentially influence crop VOC emissions in the next through soil legacy effects, illustrating additional avenues through which cropping systems may be leveraged to enhance pest management.

The aim of this work was to verify the possibility of intercropping rice with green manures, as well as the impact of the dry biomass yield of these intercropping systems on common bean in succession, evaluating the agronomic and qualitative performance of grains from both crops. The experiment was conducted in Southeastern Brazil in the years 2018 and 2019, with succession of rice (spring/summer) and common bean (autumn/winter). The treatments were composed of cropping systems with rice as a sole crop and intercropped with forage peanut, calopo, Crotalaria breviflora, Crotalaria spectabilis, stylo, jack bean and dwarf pigeon pea. No intercropping increased the system's yield compared to sole-crop rice, but intercropping of rice with forage peanut and stylo promoted grain yield and quality similar to those of sole-crop rice. Intercropping with C. breviflora affected the agronomic and qualitative performance of rice. Common bean yield after rice intercropped with dwarf pigeon pea, C. spectabilis and C. breviflora was similar in yield after sole-crop rice, while the other intercrops reduced common bean yield. Common bean grain quality was not affected by the cultivation of rice as sole crop and intercropped with green manures. Although none of the intercropping systems increased yield compared to sole-crop rice (control), it can be concluded that the intercropping of upland rice is viable depending on the green manure species, allowing greater biomass production per area that can help long-term soil conservation and increase the system's yield.

Across the Midwest, substantial funding and personnel time have been allocated to encourage farmers to adopt a wide range of conservation practices but adoption rates for many of these practices remain low. Prior research focuses largely on the influence of individual-level factors (e.g., beliefs, attitudes) on conservation practice adoption rather than on contextual factors (e.g., seasons) that might also play a role. In the present study, we considered seasonal variation and its potential influence on farmer cover crop decision-making. We first established how farmer temporal and financial resources fluctuate across the year and then compared the annual agricultural decision and cover crop decision calendars. We also considered farmer cover crop perceptions and likely behaviors. To study this, we surveyed the same Midwestern farmers in the spring, summer and winter within a 12-month period. Results indicated that farmers were generally the least busy and the most financially comfortable in the winter months. Moreover, farmers perceived the benefits of cover crops differently throughout the year. These results indicate that seasonality can be a confounding factor which should be considered when designing and conducting research and farmer engagement. As researchers, it is our responsibility to understand the specific calendar experienced by our sample and how that may influence responses so we can examine theory-supported factors of interest rather than seasonality as a driver of farmer responses. As practitioners, it is important to use research findings to engage with farmers about conservation in a way that prioritizes communicating about the most salient aspects of the practice at the time of year when farmers will be most receptive.

With the increasing focus on herbicide-resistant weeds and the lack of introduction of new modes of action, many producers have turned to planting annual cover crops as a method for reducing weed populations. Recent studies have suggested that perennial cover crops such as white clover could be used as living mulch. However, white clover is slow to establish and is susceptible to competition from winter weeds. Therefore, the objective of this study was to determine clover tolerance and weed control in established stands of white clover to several herbicides. Studies were conducted in the fall and winter of 2018 to 2019, and 2019 to 2020, at the J. Phil Campbell Research and Education Center in Watkinsville, GA, and the Southeast Georgia Research and Education Center in Midville, GA. POST applications of imazethapyr, bentazon, or flumetsulam at low and high rates, or in combination with 2,4-D and 2,4-DB, were applied when clover reached the 2- to 3-trifoliate stage. Six weeks after the initial POST application, a sequential application of bentazon and flumetsulam individually, and combinations of 2,4-D, 2,4-DB, and flumetsulam, were applied over designated plots. Clover biomass was similar across all treatments except where it was reduced by sequential applications of 2,4-D + 2,4-DB + flumetsulam in the 2019 to 2020 season, indicating that most treatments were safe for use on establishing living mulch clover. A single application of flumetsulam at the low rate or a single application of 2,4-D + 2,4-DB provided the greatest control of all weed species while minimizing clover injury compared with the nontreated check. These herbicide options allow for control of problematic winter weeds during clover establishment, thereby maximizing clover biomass and limiting canopy gaps that would allow summer weed emergence.

Replacing tillage with cover crops (CC) for weed management in corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] systems with mechanical weed control has many soil health benefits but in the western Corn Belt, CC establishment after harvest is hampered by cold temperatures, limited labor and few compatible CC species. Spring-planted CC may be an alternative, but information is lacking on suitable CC species. Our objective was to evaluate four spring-planted CC with respect to biomass production and weed suppression, concurrent with CC growth and post-termination. Cover crop species tested were oat (Avena sativa L.), barley (Hordeum vulgare L.), brown mustard [Brassica juncea (L.) Czern.] and yellow mustard (Brassica hirta Moench). They were compared to no-CC treatments that were either tilled pre- and post-planting of soybean (no-CC tilled) or not tilled at all (no-CC weedy). CC were planted in late March to early April, terminated 52–59 days later using an undercutter, and soybean was planted within a week. The experiment had a randomized complete block design with four replications and was repeated for 3 years. Mustards and small grains produced similar amounts of biomass (1.54 Mg ha−1) but mustard biomass production was more consistent (0.85–2.72 Mg ha−1) than that of the small grains (0.35–3.81 Mg ha−1). Relative to the no-CC weedy treatment, mustards suppressed concurrent weed biomass in two out of 3 years, by 31–97%, and small grains suppressed concurrent weed biomass in only 1 year, by 98%.

Six weeks after soybean planting, small grains suppressed weed biomass in one out of 3 years, by 79% relative to the no-CC weedy treatment, but mustards did not provide significant weed suppression. The no-CC tilled treatment suppressed weeds each year relative to the no-CC weedy treatment, on average 87%. The ineffective weed control by CC reduced soybean biomass by about 50% six weeks after planting. While spring-planted CC have the potential for pre-plant weed control, they do not provide adequate early season weed suppression for soybean.