Crimson Clover Research Articles

Reconciling plant and microbial ecological strategies to elucidate cover crop effects on soil carbon and nitrogen cycling

Abstract Plant economics, the way plants allocate and utilize resources, affect multiple soil processes through interactions with root and associated microbial communities. However, the interplay between plant economics and microbial ecological strategies remains poorly understood, which is crucial for integrated manipulation of plant‐ and microbe‐mediated functions in mitigating climate change and sustaining soil health. We used a field experiment with 11 cover crop species grown monocultures in the same base soil to test whether microbial ecological strategies are associated with plant economic strategies and if their interactions are linked to soil functions. A principal component analysis (PCA) was performed on root and leaf traits to identify the loadings of cover crop species on the plant trait space. Metagenomic analysis of rhizosphere microbial communities was conducted to infer their ecological strategies based on genetically encoded community‐aggregated traits. We found a synchronous relationship between the conservation gradient of plant economic strategies and the trade‐offs in microbial ecological strategies. Conservative plant strategists, such as Lolium multiflorum, Triticum turgidum and Brassica juncea, fostered microbial communities characterized by high growth yield potentials (Y‐strategies). This included increased microbial carbon fixation pathways, citrate cycle, ribosome and valine, leucine and isoleucine biosynthesis. As a result, microbial metabolic efficiency improved, shown by higher microbial biomass carbon content and a lower metabolic quotient (qCO2), led to enhanced soil organic carbon accumulation. In comparison, acquisitive plants like Astragalus sinicus, Vicia villosa, Trifolium incarnatum and Medicago sativa stimulated microbial resource‐acquisition strategies (A‐strategies). This included enhanced bacterial chemotaxis, secretion systems, biotin metabolism and cell motility pathways, which in turn increased soil exoenzyme activity and accelerated soil nitrogen mineralization. Consequently, these species enhanced soil nitrogen availability and had substantial feedbacks on subsequent main crop productivity. Synthesis. This study demonstrates how plant economic strategies influence the balance between different microbial ecological strategies, specifically the trade‐offs in Y‐ and A‐strategies. These interactions exert control over carbon and nitrogen dynamics in the soil ecosystem. The findings provide insights for implementing nature‐based solutions to improve agroecosystem management practices.

394 Cover crops for efficient grazing systems

Abstract Grazing of cool-season cover crops provides a sustainable solution for extending the grazing season while potentially reducing the environmental impact of conventional row-crop farming practices. The primary objective of this study was to evaluate how different mixtures of cover crops affect stocker performance when grazed. The study was conducted across 18 paddocks that were sown with grass [‘Coker’ oat (Avena sativa)], grass + legume [‘Dixie’ crimson clover (Trifolium incarnatum)], or grass + legume + brassica [‘Turnip’ brassica (Brassica rapa subsp.; rapa)] at the Wiregrass Research and Extension Center in Headland, AL. These paddocks were randomly assigned to either grazed or un-grazed conditions (n = 3). In this study, yearling beef steers with an average body weight (BW) of 266 ± 44 kg were grazed in paddocks using the put and take method to maintain a forage allowance of 1 kg dry matter per kilogram of BW. Forage samples were collected biweekly to analyze biomass, botanical composition, and forage nutritive value. Grazing occurred from January 17 to March 22, 2023 (65 d). Steer BW were recorded at the beginning and end of the grazing season to calculate average daily gain. The data were subjected to analysis as a two-way ANOVA using Glimmix in SAS 9.4 (SAS Institute, Cary, NC), harvest date was considered a repeated measure. No treatment × grazing interaction was observed on forage yield performance [average (AVG) forage yield kg DM/ha; P = 0.460]. In addition, no difference was observed among the different cover crop mixtures (AVG forage yield kg DM/ha; P = 0.670). Grazed paddocks had a greater crude protein when compared with ungrazed paddocks (Grazed vs. Ungrazed %; P = 0. 017). However, there was no effect of cover crop mixture on crude protein (CP) concentration (AVG CP %; P = 0.670 for treatment effect). These results indicate that cool-season annual cover crops can provide sufficient forage yield and quality to support sufficient animal gains, even during the relatively short grazing season. Incorporating cover crops not only improves agricultural sustainability but can also enhance the resilience and long-term health of the agroecosystem.

Hydrolysates from cauliflower and artichoke industrial wastes as biostimulants on seed germination and seedling growth: a chemical and biological characterization.

Cauliflower (Brassica oleracea L.) and globe artichoke (Cynara scolymus L.) are vegetables with a high waste index mainly related to stems and leaves. In this study, enzymatic hydrolysates obtained from these wastes were proposed to be used as plant biostimulants. Life cycle assessment methodology was also applied to evaluate environmental performances related to cauliflower and artichoke byproducts. Hydrolysates (HYs) were chemically and biologically characterized. Amino acids, organic acids, amines, polyols, mineral elements, phenols, tannins, flavonoids and sulfur compounds were identified and quantified by means of NMR, inductively coupled plasma mass spectrometry and UV-visible analyses. Cauliflower leaf and flower HYs showed the highest concentration of free amino acids, whereas stems showed the highest concentration of Ca. Regarding artichoke, asparagine, glutamine and aspartic acid were exclusively detected in stems, whereas artichoke leaves showed the highest Mg and Mn levels together with the highest antioxidant activity. The HYs diluted in water were tested as biostimulants. The impacts of five concentrations of HYs (0.00, 0.28, 0.84, 2.52 and 7.56 g L-1) on seed germination and early seedling growth of crimson clover, alfalfa, durum wheat and corn were investigated. The application of artichoke biostimulant (0.28 g L-1) positively influenced the coefficient of velocity of germination in alfalfa, crimson clover and durum wheat, whereas cauliflower biostimulant significantly improved corn germination speed. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Clay soil amendment suppressed microbial enzymatic activities while increasing nitrogen availability in sandy soils

AbstractConservation management practices often produced positive but limited desirable outcomes in US Southeast sandy soils, likely due to their intrinsically low clay contents that constrain the soil's capacity to preserve organic carbon (C) and nutrients. In the field, we tested the effectiveness of a novel approach, that is, clay soil amendment, to improve sandy soils. In October 2017, clay‐rich soils (25% clay) were spread at 25 metric tons ha−1 and tilled onto a sandy soil (1.9% clay) in the field, which was further mixed by light tillage at 0‐ to 15‐cm depth, followed by planting winter cover crop mixtures (cereal rye, crimson clover, and winter pea). The crop rotation was cotton and corn with cover crop mixtures planted in the winter fallow season. Soils (0–15 cm) were collected in August 2021 and subjected to physio‐biochemical analyses. Clay amendment increased soil clay content to 3.4%, which improved nitrogen (N) availability by 51% but inhibited the activities of C (β‐d‐cellubiosidase [CB]; β‐xylosidase [BX]; N‐acetyl‐β‐glucosaminidase [NAG]) and N (leucine aminopeptidase [LAP]) cycling enzymes, resulting in up to 78% reduction in microbial respiration. A follow‐up kinetic study on BG and LAP enzymes suggested that clay addition can have different impacts on enzymes with diverse biological origins through distinct mechanisms. Clay addition can potentially improve sandy soils by stabilizing the organic inputs in soils. However, more research is required to understand its long‐term impacts making this approach practical.

Cover crop quality and quantity influences organic corn performance more than soil context

AbstractCover cropping is a common practice among organic growers, well-known for its potential to supply nitrogen (N) to subsequent cash crops. Uncertainties and challenges exist in understanding how cover crops interact with soil properties and management practices across organic farms to supply N, and if such N supply is synchronous with subsequent cash crop N demand. An on-farm study examined cereal rye (Secale cereale) versus crimson clover (Trifolium incarnatum) planted before corn (Zea mays L.) in five organic farms in Michigan with a range of soil properties and management practices. High quality crimson clover residue [Carbon (C):N ratio 15:1] was associated with higher soil inorganic nitrogen, corn chlorophyll content, tissue N content, and grain yields relative to low quality cereal rye residue (C:N ratio 25:1). There were several lines of evidence that low quality cereal rye residue coupled with substantial biomass and a dry season limited N release during peak corn N demand. Nitrogen uptake efficiency (NUE, ratio of total N removed by corn to total N input) was above 1 for corn farms with low soil organic matter (SOM), active N and C pools, and lower than 1 for farms with high SOM and active N and C pools. Overall, cover crop biomass and cover crop quality was a more important driver of corn performance than background SOM content in organic corn farms. Our research highlights the challenges of ensuring sufficient N supply in organic field production, and the importance of planting a legume cover crop before corn.

A mixture of grass-legume cover crop species may ameliorate water stress in a changing climate.

Climate change models predict increasing precipitation variability in the mid-latitude regions of Earth, generating a need to reduce the negative impacts of these changes on crop production. Despite considerable research on how cover crops support agriculture in a changing climate, understanding is limited of how climate change influences the growth of cover crops. We investigated the early development of two common cover crop species-crimson clover (Trifolium incarnatum) and rye (Secale cereale)-and hypothesized that growing them in the mixture would ameliorate stress from drought or waterlogging. This hypothesis was tested in a 25-day greenhouse experiment, where the two factors (species number and water stress) were fully crossed in randomized blocks, and plant responses were quantified through survival, growth rate, biomass production and root morphology. Water stress negatively influenced the early growth of these two species in contrasting ways: crimson clover was susceptible to drought while rye performed poorly under waterlogging. Per-plant biomass in rye was always greater in mixture than in monoculture, while per-plant biomass of crimson clover was greater in mixture under drought. Both species grew longer roots in mixture than in monoculture under drought, and total biomass of mixtures did not differ significantly from the more-productive monoculture (rye) in any water condition. In the face of increasingly variable precipitation, growing crimson clover and rye together has potential to ameliorate water stress, a possibility that should be further investigated in field experiments.

Winter cover crop performance in the Southern Piedmont region of South Carolina

AbstractCover crops (CCs) offer in‐field and environmental benefits when integrated into cropping systems. Low CC adoption in the Southern Piedmont region of South Carolina is partially due to the lack of information on CC performance and benefits within the region. To address this, eight winter CCs and a fallow/pigweed (Amaranthus spp.) treatment were investigated for their influence on soil temperature, volumetric water content (VWC), percent cover, biomass, and the occurrence of soil water repellency (SWR). A randomized complete block design experiment was conducted in the fall and winter of 2021–2022 (EXP A) and repeated in 2022–2023 (EXP B). Experiments were treated separately as methods were revised for EXP B. CCs minimally influenced soil VWC over both experiments with no consistent trend. CC did not influence soil temperatures during EXP A. In EXP B, the fallow/pigweed had the highest soil temperatures on two (out of 10) measuring events (p < 0.05). No SWR was found in either experiment. Establishment and fresh and dry CC biomass were most likely influenced by air temperatures and daylight hours driving germination during days with minimal rainfall. In both experiments, annual rye (Lolium multiflorum) produced cover quickly and yielded high biomass. Crimson clover (Trifolium incarnatum) took longer to establish but also yielded one of the highest biomasses. This study demonstrated that winter CCs had little influence on soil physical properties and that while cereal rye (Secale cereale) is a common CC utilized for erosion control, the greater biomass and surface roots of annual rye make it a superior CC for use in Southern Piedmont agroecosystems.

Assessing the long‐term effects of conservation agriculture on cotton production in Northeast Louisiana using the denitrification–decomposition model

AbstractConservation agriculture (CA) aims to sustain agricultural production, soil, and environmental health in agroecosystems and has been promoted throughout the United States. The adoption of CA in cotton (Gossypium hirsutum) systems provides both agronomic and environmental benefits. Yet, there is limited information on the long‐term effects of CA practices on crop yield and adaptation strategies. An integrated CA system, that is, cover crops with no‐tillage (NT) instead of conventional agriculture, was implemented in the long‐term field experiments and assessed with an integrated biogeochemical model. Using the denitrification–decomposition model, this study estimated the effects of four different cover crops, for example, native grass (NG), hairy vetch (Vicia villosa), winter wheat (Triticum aestivum L.), and crimson clover (Trifolium incarnatum), on cotton yield under four different nitrogen (N) levels (e.g., 0, 50, 100, and 150 kg N/ha) and estimated responses on carbon (C) sequestration, and ecosystem functionality over a 10‐year study. The NT‐NG 50 N was used as a calibration dataset to accurately estimate the cotton lint yield with a normalized root mean square error (NRMSE) of 21% and model efficiency of 0.3. The calibration data validated the effects of hairy vetch, winter wheat, and crimson clover under the NT‐50 N with NRMSE of 24%, 21%, and 25%, respectively. According to the scenario analysis, the 50 kg N/ha application with a single‐irrigation event (10‐cm depth) was most beneficial for maximizing the cotton yield with cover crop incorporation at the NT system over the long term. The effects of increasing cover crop biomass (i.e., double seed rate) on C content, regardless of N application rates, varied based on the relationship between the main and cover crop species. Besides, the furrow plow tillage system provided efficient C sequestration. The proposed approach stands to provide agricultural and environmental sustainability with the implementation of cover crop or crop residue incorporation instead of increased N application, seed rates, and irrigation events under NT practices.

Evaluation of single and mixed cover crops species in a sandy loam soil under corn production

AbstractInformed selection of cover crop species is critical for optimizing their benefits by considering the costs of adoption and potential initial negative impact on yields against the proven benefits for sustainable production. The Lower Mississippi Delta region is lagging in cover crop adoption, partly due to a paucity of this information from the area, despite being one of the major row crop‐producing regions in the United States. Common cover crop species in the region, cereal rye (CR) (Secale cereale), hairy vetch (HV) (Vicia villosa), and crimson clover (CC) (Trifolium incarnatum), and their possible two‐ and three‐combination mixes were evaluated for their impact on biomass production, enzyme activities, nutrient cycling, and corn (Zea mays) yields. HV + CC + CR and HV + CR produced the highest biomass and lowest yields compared to all treatments. HV and CC produced the least biomass but comparable yields to no cover crop. HV + CC + CR, HV + CR, CR, CC, and HV treatments had comparable total nitrogen, phosphorus, and soil organic carbon levels in the surface 0‐ to 5‐cm depth. Generally, CC alone and the HV + CR mix consistently displayed significantly higher phosphatase, N‐acetylglucosaminidase, β‐glucosidase, and cellobiohydrolase activities compared to all other treatments, while CR had the lowest. The single species of CC or HV may be the best option in the short term for initial cover crop implementation, rotating with CR a few years down the line for optimum long‐term benefits under corn production in this region.

The Impact of Peach Rootstocks and Winter Cover Crops on Reproduction of Ring Nematode

Two peach rootstocks (‘Guardian’ and ‘MP-29’) and ten winter cover crops (rye, wheat, barley, triticale, oat, Austrian winter pea, crimson clover, balansa clover, hairy vetch, and daikon radish) were evaluated in a greenhouse environment to determine their suitability to host ring nematode, Mesocriconema xenoplax. Each crop was inoculated with 500 ring nematodes, and the experiments were terminated 60 days after inoculation. The reproduction factor (ratio of final and initial nematode population) ranged from 0 to 13.8, indicating the crops greatly varied in their host suitability to ring nematode. ‘Guardian’ has been known to tolerate ring nematode; however, results from the current study suggest the tolerance statement is anecdotal. Another peach rootstock, ‘MP-29’, was also a good host for ring nematode, suggesting an urgency to develop ring nematode-resistant peach rootstocks. Wheat supported the least to no nematode reproduction while pea supported the greatest reproduction. The rest of the cover crops were poor to good hosts to ring nematodes. Although planting cover crops in peach orchards is not common, employing non or poor host crops can help suppress nematodes in addition to having soil health benefits. Furthermore, peach breeding programs should focus on finding and introgressing ring nematode resistance in commercial rootstocks.

Effect of cover crops on soil health at different landscape positions

AbstractSoil health is crucial to reaching high yields, and growing cover crops can help improve soil conditions. The goal of this study is to determine the effects of cover crops on soil health using potential respiration, potential nitrogen mineralization, and aggregates stability as indicators of soil health. The study has been conducted since 2019 at the University of Kentucky Spindletop Farm, Lexington, KY, and involves three landscape positions receiving a treatment with cereal rye, cereal rye–crimson clover mixture, and fallow soil. This study emphasized that cover crops can enhance potential respiration and microbial activity over landscape positions, with rye being more beneficial than the mixture treatment. However, cover crops were also beneficial for aggregate stability but not for potential nitrogen mineralization.

Soil thermal properties: influence of no-till cover crops

Soil thermal properties, which determine heat transport, can influence soil health parameters and crop productivity. The objective of this study was to evaluate the 2-year effects of no-till cover crops (CCs) and no-till no cover crop (NC) on soil thermal properties (thermal conductivity (λ), volumetric heat capacity ( CV), and thermal diffusivity ( D)). Two levels of CCs were used for this study: CC versus NC. The CCs included crimson clover ( Trifolium incarnatum L.), hairy vetch ( Vicia villosa Roth.), winter peas ( Lathyrus hirsutus L.), oats ( Avena sativa), winter wheat ( Triticum aestivum L.), triticale ( Triticale hexaploide Lart.), flax ( Linum usitassimum L.), and barley ( Hordeum vulgare L.). Soil samples were collected at 0–10, 10–20, and 20–30 cm depths and their λ, CV, and D were measured in the laboratory. Additionally, soil organic carbon, bulk density (BD), and volumetric water content (ϴ) at saturation, −33 kPa, and −100 kPa soil water pressures were measured. Results showed that BD was 18% and 14% higher under CC compared with NC management during 2021 and 2022, respectively. Furthermore, ϴ at all measured soil water pressures was slightly higher under CC compared with NC management during both years. As a result, λ and D were significantly higher under NC compared with CC management, while CV was significantly higher under CC compared with NC management, during both years and at all measured soil water pressures. Generally, soil thermal properties were directly proportional to ϴ, suggesting that ϴ may be the most important factor influencing soil thermal properties.

89 Improving cattle grazing efficiency with multi-functional cover crops

Abstract Grazing cool-season cover crops provides a sustainable way of extending the grazing season and reducing the impact row-crop farming systems on the environment. Cover crops promote soil health; however, the impacts of grazing cover crops on soil health in the Southeast are not well understood. The objective of the current study was to determine the effects of different cover crop mixtures on a cotton (Gossypium hirsutum)-peanut (Arachis hypogaea) cropping system. The experiment consisted of 18 paddocks, planted in mixtures of grass [‘Coker’ oat (Avena sativa)], grass + legume [‘Dixie’ crimson clover (Trifolium incarnatum)], or grass + legume + brassica [(‘T-raptor’ brassica (Brassica napus × B. rapa)] planted at the Wiregrass Research and Extension Center (Headland, AL). Paddocks were randomly allocated to grazed or not grazed (n = 3). Grazed paddocks were grazed with yearling beef steers (266 ± 44 kg) using the put and take method to maintain a forage alloance of 1 kg DM per kg BW. Forage samples were collected every 2 wk, for biomass, botanical compositions, and nutritive value. Paddocks were grazed from 17 Jan – 22 Mar 2023 (65 d) and steer BW were taken at the beginning and end of the grazing season for calculation of average daily gain Data were analyzed using Proc Glimmix of SAS 9.4 (SAS Institute, Cary, NC) with forage sampling date considered a repeated measure. No difference in steer average daily gain was detected among grazed treatments (1.5 kg/d; P > 0.44). Cover crop (forage) biomass was also not different among all grazed and ungrazed treatments (1,097 kg DM/ha; P = 0.56). According to the results, grazing cool-season annual cover crops may reduce the supplementation required to maintain cattle through the winter months in the Southeast.

Assessing relationships of cover crop biomass and nitrogen content to multispectral imagery

AbstractCover crops provide valuable roles in sustainable agriculture, provided they produce enough biomass. To accurately measure their services to field management, spatial estimates would be useful to producers. This study used multispectral drone imagery to produce maps of normalized difference vegetation index (NDVI), normalized difference red edge index (NDRE), and a digital surface model (DSM) of cover crop plots on sandy, Mid‐Atlantic soils. Cover crops included cereal rye (Secale cereale), mixtures of rye and crimson clover (Trifolium incarnatum), and mixtures of rye and hairy vetch (Vicia villosa). Their biomass was sampled in the spring of 2019, 2020, and 2021, dried, weighed, and analyzed for total nitrogen (N) content. Measurements of NDVI became saturated (i.e., reached a linear plateau) at 3.86 Mg biomass ha−1, NDRE at 5.72 Mg biomass ha−1, and the DSM at 5.11 Mg biomass ha−1. The measured N content became saturated at 80.9, 139.1, and 75 kg N ha−1 for NDVI, NDRE, and the DSM, respectively. Based on log transformations, NDVI was a stronger predictor of biomass and N, but not C:N. The NDRE was important for biomass, N, and C:N, while the DSM interactions with cover crop species helped predict both the N content and C:N of cover crop tissues. Accumulated growing degree days was important as an individual variable for biomass and N and as an interaction with cover crop species.

No‐till cover crop effects on the hydro‐physical properties of a silt loam

AbstractSoil hydraulic and physical properties can be influenced by various land management practices, and they determine water movement and storage within the vadose zone, with both agronomic and environmental effects. The objective of this study was to evaluate the effects of two such practices (no‐till [NT] and cover crops [CCs]) on soil hydraulic (e.g., saturated hydraulic conductivity [Ksat], and water retention) and physical (e.g., bulk density [BD], pore size distribution, air‐filled pore spaces [AFPSs], and water‐filled pore spaces [WFPSs]) properties. The CCs used included crimson clover (Trifolium incarnatum L.), hairy vetch (Vicia villosa Roth.), winter peas (Lathyrus hirsutus L.), oats (Avena sativa), winter wheat (Triticum aestivum L.), triticale (Triticale hexaploide Lart.), flax (Linum usitassimum L.), and barley (Hordeum vulgare L.). Soil samples were collected and analyzed during 2021 and 2022 right before CC termination at 0‐ to 10‐cm, 10‐ to 20‐cm, and 20‐ to 30‐cm depths. Results showed that, during 2021 and 2022, BD was 18% and 14% higher, respectively, under NC compared with CC management, while Ksat was 2.2 and 1.9 times higher, respectively, under CC compared with NC management. Further, the non‐capillary pores were significantly (p ≥ 0.05) higher under CC compared with NC management during both years of study. As a result, the majority of the total pores under CCs were filled with air, while the majority of total pores under NC management were filled with water. Therefore, this CC mix may be useful in lengthening the growing period during wet seasons by increasing air‐filled pore spaces.

Soil texture, fertilization, cover crop species and management affect nitrous oxide emissions from no-till cropland

Cover crops reduce nitrate leached, but effects on nitrous oxide (N2O) emissions are mixed. Cover crops can reduce N2O emissions by reducing levels of mineral nitrogen (N) and surface soil moisture during spring. Cover crops can also increase N2O emissions by adding organic substrates, releasing N during decomposition, or increasing summer soil water content. Winter-killed cover crops can increase soluble organic C and N during periods of typically low microbial activity. We hypothesized that planting a cover crop mix of radish (Raphanus sativus)-crimson clover (Trifolium incarnatum)-rye (Secale cereale) would increase direct N2O emissions relative to no cover crop, and result in lower direct and indirect N2O emissions than planting radish alone. We also hypothesized that extending the cover crop growing season, by planting earlier and killing later, would increase direct N2O emissions during winter, decrease direct N2O emissions during summer, and decrease indirect N2O emissions. To address these hypotheses, we conducted two field experiments (on sandy and silty soils) over four site-years. We measured cover crop biomass and N content, soil mineral N concentrations, soil moisture, green canopy cover, soil porewater nitrate, direct N2O emissions, and estimated indirect N2O emissions. Nitrous oxide emissions were ~ 7.8 times greater at the silty than the sandy sites due to greater soil moisture retention. Site-years with high radish biomass exhibited greater direct N2O emissions than sites with low radish biomass following winter-kill. Indirect N2O emissions were decreased ~7 % by planting cover crops and by ~70 % by planting cover crops early. Fertilizer induced emission peaks were 8.2 times greater than all previous N2O emissions combined at a silty site. Our results suggested that soil texture and fertilization played an important role in direct N2O emissions, while cover crop species, biomass, and timing played a more important role in NO3 leached, and thus, indirect N2O emissions.

Screening suitable legumes for living mulches to support nitrogen dynamics and weed control in a durum wheat-forage sorghum crop sequence

Relay intercropping of service legumes (living mulch) is a valuable agroecological practice to support nutrient availability, yield and non-chemical weed control in a crops sequence, if suitable legumes are chosen. This study tested the suitability of eight legume living mulches for relay intercropping in durum wheat (Triticum durum Desf.) evaluating their effects on the subsequent forage sorghum (Sorghum bicolor L. Moench) in a Mediterranean low-input cereal-based cropping system. Legumes include perennial (Medicago sativa, Medicago lupulina, Trifolium repens, Hedysarum coronarium), annual (Trifolium incarnatum, Trifolium resupinatum) and annual self-seeding (Trifolium subterraneum, Medicago polymorpha) species. A plot experiment repeating two times a wheat-sorghum crop sequence, was carried out in Central Italy to assess the effects of relay intercropping of legumes on agronomical and economic performance of the associated wheat and subsequent sorghum. The legumes were undersown in the already developed durum wheat in late winter. They were maintained after wheat harvest and used as green manure by biomass chopping and plowing in the following spring at sorghum sowing time. None of the intercropped legumes affected N uptake or grain protein content of the companion wheat with respect to the control (wheat sole crop). In the spring before sorghum sowing, N input from legume biomass residues was assessed and it sensibly changed according to legume species, ranging from 1.2 (T. incarnatum) to 182 kg ha−1 (H. coronarium). The legume treatments significantly affected the N uptake in the subsequent sorghum and it ranged from 20.2 to 172.6 kg ha−1. Without the use of additional external nitrogen input, average sorghum dry biomass production preceded by H. coronarium (13.3 t ha−1), T. repens (11.8 t ha−1), T. subterraneum (11.0 t ha−1) and M. sativa (9.3 t ha−1) was in line with the productive level under conventional conditions. Biomass residues of M. sativa significantly reduced the total weed biomass in sorghum by 65% compared with the control. In sorghum, preceding legumes such as T. resupinatum and T. incarnatum promoted dicotyledonous weed growth. Hedysarum coronarium and T. repens were the best legumes for relay intercropping in the low-input wheat-sorghum crop sequence under Mediterranean conditions of this study according to agronomic and economic evaluation. These legumes were able to increase soil nitrogen content allowing to significantly reduce external nitrogen fertilization while optimizing sorghum production. When gross income is calculated at cropping system level, most legumes provide a positive economic balance.

Integrating cover crops and herbicides for weed control in soybean

Abstract In mid-southern, southeastern, and northeastern U.S. soybean production regions, the evolution of herbicide-resistant weeds has become a significant management challenge for growers. The rising herbicide costs for managing herbicide-resistant weeds are also a growing concern, leading to the utilization of cover crops as an integrated weed management strategy for addressing these challenges. Field experiments were conducted at two locations in Alabama in 2022 to evaluate winter cereal cover crops, including a mixture and herbicide system integration in soybean. Treatments included five cover crops: oats, cereal rye, crimson clover, radish, and a cover crop mixture. Cover crops were evaluated for their weed-suppressive characteristics compared to a winter fallow treatment. Additionally, four herbicide treatments were applied: a preemergence (PRE) herbicide, a postemergence (POST) herbicide, PRE plus POST herbicides, and a nontreated (NT) check. The PRE herbicide was S-metolachlor; the POST treatment contained a mixture of dicamba and glyphosate. The PRE plus POST system contained the PRE application followed by POST application. Results show that cereal rye and the cover crop mixture provided weed biomass reduction compared to all cover crop treatments across both locations. Furthermore, we observed greater soybean yield following the cereal rye cover crop than following the winter fallow treatment at one location. POST and PRE plus POST herbicide treatment resulted in greater weed biomass reduction and improved soybean yield than the PRE herbicide treatment alone and the NT check at both locations.

Legume cover crop as a primary nitrogen source in an organic crop rotation in Ontario, Canada: impacts on corn, soybean and winter wheat yields

This study presents results from the first 5 years of an organic cropping trial in Ontario, Canada, where legume cover crops were the primary nitrogen source in a soybean-winter wheat/cover crop-corn rotation. Treatments included cover crop termination using moldboard plow (MP) or chisel plow (CP), a no-cover crop control under conventional production (CK-C), and four cover crops including summer-seeded crimson clover (CC, Trifolium incarnatum L.), summer-seeded hairy vetch (HV, Vicia villosa L. Roth), summer-seeded red clover (RCss, Trifolium pratense L.), and frost-seeded red clover (RCfs). Summer-seeding occurred after wheat harvest (July–August), and frost-seeding occurred in early spring (March–April). At cover crop termination, average aboveground cover crop biomass ranged from 5.9 to 8.1 Mg ha−1, while accumulated biomass nitrogen ranged from 155 to 193 kg ha−1. Corn grain yields were 11.6 Mg ha−1 for MP and 10.2 Mg ha−1 for CP tillage-termination method; and 13.3 Mg ha−1 for CK-C, 10.9 Mg ha−1 for RCfs, 10.6 Mg ha−1 for HV, 10.2 Mg ha−1 for CC, and 9.5 Mg ha−1 for RCss. Organic winter wheat yields were nitrogen-limited, averaging 27% lower than CK-C. Winter wheat yields were 10–15% lower in the RCfs than in other summer-seeded cover crop treatments. Soybean yields were largely unaffected by the treatments. It was concluded that summer-seeded legume cover crops are an effective primary nitrogen source for corn, but not as effective for the winter wheat phase of the soybean-winter wheat-corn rotation.

Effectiveness of solitary and combined use of cover crop species to manage soilborne diseases in woody ornamental nursery production system

The understanding of how solitary and combined use of covercrop species and seeding rates influences soilborne diseases is lacking. Cover crops (crimson clover, triticale and crimson clover + triticale) were seeded in the field plots in September 2019 (Trial 1) and September 2021 (Trial 2) at two seeding rates (low and high) and a no cover cropped fallow served as a control. The soil was collected from all the plots in the following June. Red maple rooted cuttings were planted in nursery containers filled with those soils and plant health was evaluated with and without inoculation with Phytophthora nicotianae, Phytopythium vexans and Rhizoctonia solani. Plant height and fresh weight were measured, and plant roots were assessed for root rot severity (0–100% roots affected) and pathogen recovery. The number of fluorescent Pseudomonads present in soil samples was counted. Root rot severity and pathogen recovery were less with plants grown in cover cropped soil compared to non-cover cropped soil. Root rot severity caused by all three pathogens was least with the plants grown in the crimson clover and mixed cover cropped soil with the mixture being better than crimson clover. Moreover, plants grown in the high rate of cover cropped soil had less root rot severity compared to plants grown in low seeding rate cover cropped soil. Plant fresh weight was greater for plants grown in the high rate of crimson clover cover cropped soil and, in the mixture, compared to the non-cover cropped soil, whereas height was least affected. The Pseudomonad population was greatest in mixed cover cropped as well as in the high rate of cover cropped soil. Our findings suggest that a mixture of cover crop species and high seeding rate provides better service in suppressing root rot diseases likely associated with biological processes and nutrient availability.