Cover Crop Mixtures Research Articles

Interseeding cover crops in corn

AbstractFarmers benefit from ecosystem services that cover crops provide, but time constraints limit the opportunity to seed cover crops following corn (Zea mays L.) harvest in the upper Midwest. Interseeding cover crops in corn during the early vegetative growth stages lengthens the cover crop growing season; however, cover crops may have difficulty establishing in standing corn, or conversely, compete with corn and reduce yield. The objectives of this research were to determine cover crop establishment when broadcast interseeded in corn from the V2–V7 growth stages, suppression of weeds by cover crops, and effects of cover crops on corn grain yield. Annual ryegrass (Lolium multiflorum Lam.), crimson clover (Trifolium incarnatum L.), oilseed radish (Raphanus sativus L.), and a three‐species mixture were interseeded in four site‐years in Michigan. Annual ryegrass density was highest compared with oilseed radish and crimson clover 30 d after interseeding and at harvest in October. Cover crop density was highest at the V4–V7 interseeding timings. Annual ryegrass produced more fall biomass (186 kg ha−1) compared with crimson clover (112 kg ha−1), and fall biomass was greatest at the V2, V3, and V5 interseeding timings. Spring biomass was 384 and 180 kg ha−1 for annual ryegrass and the cover crop mixture, respectively; these treatments reduced winter annual weed biomass. Corn grain yield was unaffected by cover crops at any interseeding timing. Crimson clover did not establish well in this experiment. Annual ryegrass and oilseed radish interseeded in V2–V7 corn did not reduce corn grain yield.

Cover crop diversity for weed suppression and crop yield in a corn–soybean production system in Tennessee

AbstractWeed communities may potentially reduce row‐crop yields resulting in a loss of revenue for producers. Studies have reported a decrease in the efficacy of chemical methods of weed control due to increased weed resistance. With the goal of reducing reliance on chemical weed control and promoting sustainable crop production in mind, we evaluated different winter cover crop (CC) types (single‐, double‐, and multi‐species) and CC planting methods (broadcasting vs. drilling) on CC and weed groundcover and row‐crop yield in a no‐till corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation system in Tennessee from 2013 to 2017. Our results showed that winter CC reduced spring weed ground coverage by 64–76% compared with winter fallow with no herbicide application. A five‐species CC mixture increased soybean yields by 6 to 8.5% across seeding method treatments compared with other CC treatments and winter fallow. This yield increase was more visible in a drought year. Corn, grown in years with normal weather patterns, did not show a yield response to CC types. From this study, cover cropping was found to be an effective strategy for weed control compared with leaving the field fallow without herbicide application following row‐crop harvest; however, no consistent species‐specific trends were observed on weed suppression and row‐crop yield. Future research should focus on understanding CC species composition and biomass production in double‐ and multi‐species mixtures from this field experiment to draw robust conclusions on agronomic responses of individual CC species and planting methods.

Cover Crop Mixtures Effects on Soil Physical and Chemical Properties in Japan

Cover Crop Mixtures Effects on Soil Physical and Chemical Properties in Japan

Hairy Vetch and Triticale Cover Crops for N Management in Soils

Over-application of fertilizer to cropland adversely affects both environmental and agricultural ecosystems. This study examined whether planting a legume-based winter cover crop mix offsets fertilizer application via natural nitrogen inputs. The influence of the cover crop mixture on available nutrients was also assessed. Hairy vetch (Vicia villosa) and winter triticale (×triticosecale) cover crops were planted in fall and terminated in May. Soil fertility data was collected before and after planting the winter cover crop to determine the effect on fixing nitrogen and soil phosphorus, potassium and organic matter levels. Increases of soil ammonium were observed in plots with cover crop treatments. A triticale-hairy vetch cover crop mix was successful at scavenging P for future crops and appears to hold promise for long-term soil fertility benefits.

Effects of cover crops sown in autumn on N and P leaching

AbstractA field experiment with separately tile‐drained plots was used to study the ability of oilseed radish (Rhaphanus sativus L.), as a cover crop sown after harvest of a main crop of cereals or peas, to reduce nitrogen (N) and phosphorus (P) leaching losses from a clay loam in southern Sweden over 6 years. In addition to oilseed radish in pure stand, two cover crop mixtures (hairy vetch (Vicia villosa) and rye (Secale cereale) for 3 years and oilseed radish in mixture with buckwheat (Fagopyrum esculentum) for 2 years) were tested. The cover crop plots (three replicates per treatment) were compared with unplanted plots as a control. Plots cropped with oilseed radish during autumn (August–November) had significantly smaller yearly mean N concentration in drainage water over 5 of 6 years compared with unplanted controls. Mineral N content in the soil profile in autumn was significantly less in oilseed radish plots than for control plots in all years. The cover crop mixtures of hairy vetch and rye or buckwheat and oilseed radish also showed the potential to reduce soil mineral N in autumn and N concentration in drainage water, compared with unplanted controls. The cover crops had no impact on P leaching. In conclusion, oilseed radish has the ability to reduce leaching losses of N, without increasing the risk of P leaching.

Agronomic and economic tradeoffs between alternative cover crop and organic soybean sequences

AbstractOrganic grain producers are interested in reducing tillage to conserve soil and decrease labor and fuel costs. We examined agronomic and economic tradeoffs associated with alternative strategies for reducing tillage frequency and intensity in a cover crop–soybean (Glycine max L. Merr.) sequence within a corn (Zea mays L.)–soybean–spelt (Triticum spelta L.) organic cropping system experiment in Pennsylvania. Tillage-based soybean production preceded by a cover crop mixture of annual ryegrass (Lolium perenne L. ssp. multiflorum), orchardgrass (Dactylis glomerata L.) and forage radish (Raphanus sativus L.) interseeded into corn grain (Z. mays L.) was compared with reduced-tillage soybean production preceded by roller-crimped cereal rye (Secale cereale L.) that was sown after corn silage. Total aboveground weed biomass did not differ between soybean production strategies. Each strategy, however, was characterized by high inter-annual variability in weed abundance. Tillage-based soybean production marginally increased grain yield by 0.28 Mg ha−1 compared with reduced-tillage soybean. A path model of soybean yield indicated that soybean stand establishment and weed biomass were primary drivers of yield, but soybean production strategy had a measurable effect on yields due to factors other than within-season weed–crop competition. Cumulative tillage frequency and intensity were quantified for each cover crop—sequence using the Soil Tillage Intensity Rating (STIR) index. The reduced-tillage soybean sequence resulted in 50% less soil disturbance compared to tillage-based soybean sequence across study years. Finally, enterprise budget comparisons showed that the reduced-tillage soybean sequence resulted in lower input costs than the tillage-based soybean sequence but was approximately $114 ha−1 less profitable because of lower average yields.

Decomposition of mixtures of cover crop residues increases microbial functional diversity

To improve sustainability in agricultural systems, winter cover crops are increasingly replacing fallow to stimulate soil functions that reduce nutrient losses and greenhouse gas production, reduce pests for the next cash crops, increase soil organic matter pools and reduce erosion. Several of these functions are highly dependent on soil microbes decomposing cover crop residues. Since cover crop species differ in their traits it is hypothesized that plant species residue mixtures with complementary characteristics perform better by stimulating soil microbial functional diversity. To test this, residues of cover crop monocultures and mixtures were mixed with agricultural soil in a microcosm experiment, and fungal and bacterial biomass, microbial metabolic potential, greenhouse gas emissions and soil nutrients were measured during 50 days. Fungal biomass increased for all treatments compared to the control (no additions). However, there were no significant differences between cover crop mixtures and monocultures. Biolog ECO plates were used as a proxy for the metabolic potential of the microbial community. The number of substrates used was significantly higher in soil amended with residues of cover crop mixtures indicating an increased number of substrate niches for microbes. C:N ratio of cover crop residues was shown to be an important variable in explaining dynamics of CO2 and N2O emissions. Mixtures of cover crops showed reduced N2O and CO2 emissions compared to monocultures at the start of the experiment, but did not reduce greenhouse gas emissions over the whole incubation period. Adding nitrogen to the cover crop treatment with the highest C:N ratio (oat) did increase N2O emissions, but not CO2 emissions suggesting that decomposition rate of oat residues is not limited by nitrogen availability. Overall, mixtures of cover crops stimulated microbial functional diversity in soil incubations. Although this may have positive implications for soil quality and functioning in agricultural fields, further studies are needed to verify if these results hold under field conditions.

Functional diversity of cover crop mixtures enhances biomass yield and weed suppression in a Mediterranean agroecosystem

SummaryFunctional diversity of cover crop mixtures is thought to improve biomass production and weed suppression, two key agroecosystem services in organic systems. To test this hypothesis, we selected eight cover crop species belonging to four functional groups: (i) vining growing large‐seeded legumes (field pea, common vetch), (ii) erect growing small‐seeded legumes (crimson clover, squarrosum clover), (iii) grasses (barley, oats) and (iv) Brassicaceae (radish, black mustard). Nine cover crop mixtures were designed to create a gradient of diversity in terms of number of species and number of functional groups. A control treatment and all monocrops were included in the trial. Regarding cover crop biomass, mixtures outyielded monocrops by an average of 37%. Both functional identity and composition (i.e. trait complementarity) influenced biomass production and weed suppression provided by cover crops. Regression analysis showed that increase in both species diversity and functional diversity in cover crop mixtures improved the provision of agroecosystem services. Results from this study show that complementarity of species functional traits in cover crop mixtures can be used as a strategy to ensure high biomass production and good weed suppression in changing agroecosystems.

Weed Suppression in Only-Legume Cover Crop Mixtures

Weed suppression is a potential benefit of cover crop mixtures, as species diversity may allow for combining early and late-season competition with weeds. Here, we studied if this is possible for only-legume mixtures containing species with different growth rates, by testing two legumes, alsike clover (AC; Trifolium hybridum L.) and black medic (BM; Medicago lupulina L.) in two field trials sown in 2016 and 2017. Five AC:BM ratios (100:0, 67:33, 50:50, 33:67, and 0:100) were grown at three densities (50%, 100%, and 150% of recommended seed density). Cover crop and weed aboveground biomass (CCB and WB, respectively) were harvested three times, after establishment in spring (H1), in summer (H2), and in autumn after mulching (H3). Compared to fallow plots, all monocultures and mixtures showed early-season weed suppression in terms of biomass production and more efficiency over time with an average reduction of 42%, 52%, and 96% in 2016, and 39%, 55%, and 89% in 2017 at H1, H2, and H3, respectively. Out of 54 mixture treatments, only eight mixtures showed stronger weed suppression than monocultures. Mixtures reduced WB by 28%, as an average value, in 2017 compared to the respective monocultures, but not significantly in 2016, indicating that the crop diversity effect on weeds was dependent on the growing environment. Weed suppression was significantly higher at 100% and 150% seed density than 50%, but no significant differences were determined between 100% and 150% seed density. After mulching, no density effect was observed on CCB and WB. In conclusion, AC and BM can be used as a keystone species on weed suppression for sustainable agriculture as they possess plasticity to suppress weeds when higher biomass productivity is limited by environmental conditions. However, their diversity effects are time and condition dependent. Appropriate seed density and mulching can successfully be employed in weed management, but seed density may not have an effect after mulching.

Nitrogen provisioned and recycled by cover crops in monoculture and mixture across two organic farms

Cover crops can supply and recycle soil nitrogen (N) in agroecosystems. With increasing interest in cover crop mixtures, farmers have questions about how N cycling is affected by individual species when planted alone or in mixtures. Field trials were conducted on two organic vegetable farms during the spring and summer of 2014–2016 to quantify biomass tissue N provisioned, soil nitrate (NO3-N) scavenged, and soil NO3-N mineralized from 12 species of cover crops (six spring and six summer species) planted in monoculture or five-way mixtures. All cover crops were compared to weedy and weeded (no cover crops or weeds) controls. Cover crops provisioned 28–33% more biomass tissue N than fallow weeds. Among spring cover crops, field pea produced the most biomass tissue N (131 ± 13 kg N ha−1; mean ± 1 SE) but that benefit disappeared when pea abundance was reduced in mixtures. Soil NO3-N to a depth of 0.2 m was reduced by 50–67% during cover crop and weed growth, regardless of treatment. Soil NO3-N availability approximately 1 month after incorporation of cover crop and weedy residues varied by treatment. Post-incorporation soil NO3-N was 17–19% greater in pea and soybean monocultures compared to mixtures; conversely, soil NO3-N was 17–19% lower following incorporation of buckwheat and sudangrass monocultures compared to mixtures. Results of this study demonstrate that cover crop N recycling services in near-surface soil are largely independent of species or mixture, but N provisioning services require careful management and species selection to ensure maximum biomass tissue N and timely N mineralization.

Feedbacks between nitrogen fixation and soil organic matter increase ecosystem functions in diversified agroecosystems.

Nitrogen (N) losses from intensified agriculture are a major cause of global change, due to nitrate (NO3- ) export and the eutrophication of aquatic systems as well as emissions of nitrous oxide (N2 O) into the atmosphere. Diversified agroecosystems with legume cover crops couple N and carbon (C) inputs to soil and reduce N pollution, but there is a need to identify controls on legume N2 fixation across ecosystems with variable soil conditions. Here, I tested the hypothesis that N mineralization from turnover of soil organic matter (SOM) regulates legume N2 fixation across 10 farms that spanned a gradient of SOM levels. I separated soil samples into two SOM fractions, based on size and density, which are indicators of soil nutrient cycling and N availability (free particulate organic matter and intra-aggregate particulate organic matter [POM]). This study indicates downregulation of legume N2 fixation in diversified agroecosystems with increasing N availability in intra-aggregate POM and increasing N mineralization. Intercropping the legume with a grass weakened the relationship between N in POM and N2 fixation due to N assimilation by the grass. Further, mean rates of N and C mineralization across sites increased with two seasons of a legume-grass cover crop mixture, which could enhance this stabilizing feedback between soil N availability and N2 fixation over time. These results suggest a potential mechanism for the diversity-ecosystem-function relationships measured in long-term studies of agroecosystems, in which regular use of legume cover crops increases total soil organic C and N and reduces negative environmental impacts of crop production.

Undersown cover crops have limited weed suppression potential when reducing tillage intensity in organically grown cereals

Adoption of reduced tillage in organic cropping has been slow, partly due to concerns about increasing weed infestation. Undersown cover crops (CCs) are considered to be a feasible option for weed management but their potential for weed suppression is insufficiently investigated in low-till organic cropping. The possibilities to reduce primary tillage by introducing CCs to maintain weed infestation at a level that does not substantially jeopardize crop yield were studied in a field experiment in southern Finland during 2015–2017. Eight different CC mixtures were undersown in cereals and the response in weed occurrence was consecutively assessed in spring barley, winter wheat, and finally, as a subsequent effect, in spring wheat. Growth of CCs was too slow to prevent the flush of early emerging weeds in spring barley whereas in winter wheat, CCs succeeded in hindering the growth of weeds. However, CCs could not prevent the increase of perennial weeds in a reduced tillage system in which the early growth of spring wheat was retarded in cool 2017. Consequently, after 2 years of reduced tillage, weed biomass was about 2.6 times higher and spring wheat yield was 30% lower than in plowed plots, respectively. No major differences in weed control efficacy among CC treatments were evident. A grain yield benefit was recorded after repeated use of leguminous CCs. The need for long-term field studies remains of particular interest regarding post-harvest performance and influence of CCs on perennial weeds before the inversion tillage.

Cover crop mixtures result in a positive net biodiversity effect irrespective of seeding configuration

Mixtures of plant species are often higher yielding due to species complementarities. Such effects may be beneficial to agriculture but are under-used in practice. It is therefore important to demonstrate beneficial effects of mixtures that are easy to implement for farmers. Here, we study yield in mixtures of agricultural cover crops. We hypothesized that the degree to which species express complementarity might be affected by the spatial configuration of the mixture. To test this hypothesis, we seeded mixtures using two configurations: (1) seed mixtures in each row (intimate mixing), and (2) different species in separate (alternate) rows (less intimate mixing).Three years field experiments were conducted to compare growth and N uptake by sole stands and the two pairwise mixture configurations of three cover crop species: vetch (Vicia sativa L.), bristle oat (Avena strigosa) and oilseed radish (Raphanus sativus L.). Shoot biomass production and N uptake were determined. Results were analysed using additive partitioning to determine the net biodiversity effect and its components.Mixtures, overall, accumulated significantly more shoot biomass and shoot N than the corresponding pure stands did on average; hence, the net biodiversity effect was positive. The yield benefit of mixtures (observed minus expected) was 0.66 t biomass ha−1 and 10.7 kg N ha-1 compared to an average sole cover crop of 2.58 t biomass ha−1 and 53.1 kg N ha−1. Contribution to the net biodiversity effect for biomass was, on average, equally divided between the complementarity effect and the selection effect. For N uptake, the net biodiversity effect was mostly realized through complementarity. Experimental year and species combination had a significant effect on biomass and N yield of mixtures. Mixtures containing vetch had the greatest gain in biomass compared to expectation. Whether within or between row mixing gave the highest yield and N uptake depended on species combination and year, but in most cases, the effect of configuration was not significant. Thus, overall, using cover crop mixtures resulted in a positive net biodiversity effect irrespective of seeding configuration.

Multi‐Species Cover Crop Mixtures in the Northern Great Plains

Multi‐Species Cover Crop Mixtures in the Northern Great Plains

Cover Crop Management Practices Rather Than Composition of Cover Crop Mixtures Affect Bacterial Communities in No-Till Agroecosystems.

Cover cropping plays a key role in the maintenance of arable soil health and the enhancement of agroecosystem services. However, our understanding of how cover crop management impacts soil microbial communities and how these interactions might affect soil nutrient cycling is still limited. Here, we studied the impact of four cover crop mixtures varying in species richness and functional diversity, three cover crop termination strategies (i.e., frost, rolling, and glyphosate) and two levels of irrigation at the cover crop sowing on soil nitrogen and carbon dynamics, soil microbial diversity, and structure as well as the abundance of total bacteria, archaea, and N-cycling microbial guilds. We found that total nitrogen and soil organic carbon were higher when cover crops were killed by frost compared to rolling and glyphosate termination treatments, while cover crop biomass was positively correlated to soil carbon and C:N ratio. Modifications of soil properties due to cover crop management rather than the composition of cover crop mixtures were related to changes in the abundance of ammonia oxidizers and denitrifiers, while there was no effect on the total bacterial abundance. Unraveling the underlying processes by which cover crop management shapes soil physico-chemical properties and bacterial communities is of importance to help selecting optimized agricultural practices for sustainable farming systems.

Effects of cover crops, rotation, and biological control products on soil properties and productivity in organic vegetable production in the Northeastern US

The potential benefits of different cover crops, biological control amendments, and vegetable rotation on soil chemical and biological properties, crop development and yield, and disease development in organic vegetable production, as represented by legume (green bean, Phaseolus vulgaris), cucurbit (yellow summer squash, Cucurbita pepo), and solanaceous (sweet pepper, Capsicum annuum) vegetable crops, were evaluated in a multi-year field trial in Maine, USA. Cover crops evaluated included winter rye (Secale cereale)/hairy vetch (Vicia villosa), mustard (Brassica juncea) green manure, a multi-species mixture (8 crops), and a fallow control. Overall, cover crops had only marginal effects on soil chemical properties, but all cover crops improved biological properties (microbial activity, populations, respiration) compared to fallow soil. The multi-species mixture and rye/vetch cover crops were associated with earlier emergence in beans and squash. All cover crops improved yield in beans and squash by 7–13%, but only the cover crop mixture increased yield for pepper (by 7–11%). Minimal crop diseases were observed throughout these studies, and biological control amendments, which included commercial formulations of Streptomyces, Trichoderma, and Bacillus sp., in general, did not positively affect yield, but reduced powdery mildew on squash and leaf necrosis on beans by 10–28%. The vegetable rotation also had significant effects, with beans yielding 8% higher following squash vs. pepper, squash yielding 15% higher following beans vs. pepper, and pepper yielding 11% higher following beans vs. squash. These results help define specific management practices to improve organic vegetable production and provide useful information and options for growers.

Productivity and Stability of Multi‐Species Cover Crop Mixtures in the Northern Great Plains

Core Ideas Multi species cover crops provided more stable biomass yield than single species.Grass components of cover crop mixtures were more productive than legume components.Cover crop mixtures did not use water or nitrogen differently than single species cover crops.Warm and cool season species within a functional group complemented each other.Relative LER was useful criteria to select cover crops for mixture construction. Mixed species cover crops are a relatively recent crop management method for improving soil health and cropping system sustainability. This 2‐yr study assessed the productivity and stability of cover crop mixtures with multi‐species functional groups compared with single species cover crops. Selection criteria were developed to identify suitable cover crops for a semiarid region. The study was conducted in south‐central Montana and evaluated 11 cover crop treatments which consisted of six individual species, four mixtures of these species, and a chemical‐fallow check. Biomass of cover crop mixtures was greater than single species cover crops in 2014 (p = 0.04). However, land equivalent ratio (LER) showed that cover crop mixtures did not over‐yield single species cover crops (LER ≤ 1). Cover crop mixture productivity increased where grass and taproot species were included. In contrast mixtures with legumes resulted in low overall productivity. Coefficient of variability (CV) of the functional groups was in the order of 62% > 51% > 33% for grass, taproot, and legume, respectively. Spring soil NO3–N and soil water content following cover crop mixtures were not different from single species cover crops (p > 0.05) in both years. Cover crops that produced greater biomass generally consumed more nitrogen and water. Identifying single species or mixtures with stable but acceptable biomass yield that leave greater water and soil nitrogen for the following crop is more important than maximizing biomass productivity. Species with relative LER ≥ 1 performed well within a mixture and provided a useful criterion for mixture construction.

Evaluation of legume-cereal seed mixtures for enhancement of soil fertility, carbon storage and biodiversity in a low-intensity olive orchard

The main aim of the LIFE+ OLIVECLIMA project is to trial the introduction of new cultivation practices for tree crops in order to find a cost-effective means of mitigating and adapting to climate change, through the increase of carbon sequestration by soils, and reduction of greenhouse gases emissions. In order to determine the benefits of using cover crops on soil fertility and biodiversity, an investigation with different combinations of legumes and oat has been conducted during 2014-2015 in Chania, Greece, in a low tree density rain-fed olive orchard covered dominantly by Oxalis pes-caprae weed. The treatments were: natural vegetation, bare soil, only oats, only Vicia sativa, mixture of four legumes with oats and mixture of five legumes with oats. Seed emergence and soil cover was monitored and soil was monthly sampled at three depths (0-10, 10-20 and 20-30 cm) for analysis. During plant growth, significant fluctuations in soil NO(3)-N and NH(4)-N content were recorded. Similarly, soil CO(2) emissions increased with plant growth and air temperature raise. Sowing cover crop mixtures is a promising soil management practice to increase soil fertility and enrich plant and microbial biodiversity in olive orchards especially when dominated by Oxalis pes-caprae a very aggressive weed in many Mediterranean areas.

Influence of Cultural Management on Compaction of a Cerrado Latosol

Soil compaction is a process that negatively affects the availability of water and nutrients to plants. Therefore, it is necessary to evaluate alternative practices of cultural management in order to reduce soil compaction. The experimental area is located in the Foundation for Research and Technological Development Rio Verde, where 13 treatments were installed with different systems of cultural management, all rotated with soy. A randomized complete block design (DBC) was used for this experiment, with three blocks (one repetition per block), thirteen treatments and two depths of soil (0-10 cm and 10-20 cm). Physical analyzes were soil resistance to penetration, soil density, and soil moisture at the time of collection. The treatment in which the soil was stirred during the fallow period was the one that presented the lowest resistance of the soil to penetration, followed by the treatment where a mixture of cover crops was used in the second harvest, and the treatment where soybean was harvested and brachiaria in the second crop, using corn with brachiaria every two years, was the one that presented lower soil density, followed by the treatment with stirring during fallow season. Planting areas with a greater diversity of rotating plants presented as a good proposal of soil management, as they provide ideal soil conditions for the crop and for the use of rainwater or irrigation.

Weed Control Ability of Single Sown Cover Crops Compared to Species Mixtures

To achieve efficient weed control through cover cropping, the plant species chosen needs particular consideration. Combing different cover crop (CC) species in mixtures may increase the number of provided ecosystem services, including reliable suppression of weeds. We tested the weed suppression ability of single CC species and CC mixtures in a field trial during the autumn-to-winter growing season of 2016 and 2017. Anethum graveolens L. (dill), Raphanus sativus var. oleiformis Pers. (oilseed radish), Avena strigosa Schreb. (black oat), Carthamus tinctorius L. (safflower), Vicia sativa L. (vetch) and Phacelia tanacetifolia Benth. (phacelia) were sown in monocultures, as well as in mixtures with three or six species. Treatments with favorable establishment and above-average biomass yields tended to suppress weeds by showing lower weed dry matter and weed numbers. The highest weed control efficacy within the monocultures was reached in 2017 by black oat and oilseed radish with 72% and 83%, respectively. The mixture treatments reached a generally lower soil cover, aboveground dry matter and weed control efficacy (with an average of 57% in 2017). Even though mixtures were not as effective as the best performing single sown CCs, species combinations increased resilience against adverse weather conditions, an advantage to achieving efficient weed control over a long-term period. Therefore, species composition within mixtures is more relevant than the number of species included.