Crimson Clover Research Articles

Cover crop functional types differentially alter the content and composition of soil organic carbon in particulate and mineral-associated fractions.

Cover crops (CCs) can increase soil organic carbon (SOC) sequestration by providing additional OC residues, recruiting beneficial soil microbiota, and improving soil aggregation and structure. The various CC species that belong to distinct plant functional types (PFTs) may differentially impact SOC formation and stabilization. Biogeochemical theory suggests that selection of PFTs with distinct litter quality (C:N ratio) should influence the pathways and magnitude of SOC sequestration. Yet, we lack knowledge on the effect of CCs from different PFTs on the quantity and composition of physiochemical pools of SOC. We sampled soils under monocultures of three CC PFTs (legume [crimson clover]; grass [triticale]; and brassica [canola]) and a mixture of these three species, from a long‐term CC experiment in Pennsylvania, USA. We measured C content in bulk soil and C content and composition in contrasting physical fractions: particulate organic matter, POM; and mineral‐associated organic matter, MAOM. The bulk SOC content was higher in all CC treatments compared to the fallow. Compared to the legume, monocultures of grass and brassica with lower litter quality (wider C:N) had higher proportion of plant‐derived C in POM, indicating selective preservation of complex structural plant compounds. In contrast, soils under legumes had greater accumulation of microbial‐derived C in MAOM. Our results for the first time, revealed that the mixture contributed to a higher concentration of plant‐derived compounds in POM relative to the legume, and a greater accumulation of microbial‐derived C in MAOM compared to monocultures of grass and brassica. Mixtures with all three PFTs can thus increase the short‐ and long‐term SOC persistence balancing the contrasting effects on the chemistries in POM and MAOM imposed by monoculture CC PFTs. Thus, despite different cumulative C inputs in CC treatments from different PFTs, the total SOC stocks did not vary between CC PFTs, rather PFTs impacted whether C accumulated in POM or MAOM fractions. This highlights that CCs of different PFTs may shift the dominant SOC formation pathways (POM vs. MAOM), subsequently impacting short‐ and long‐term SOC stabilization and stocks. Our work provides a strong applied field test of biogeochemical theory linking litter quality to pathways of C accrual in soil.

Episodic N2O emissions following tillage of a legume–grass cover crop mixture

Abstract. Nitrogen (N) fertilizer inputs to agricultural soils are a leading cause of nitrous oxide (N2O) emissions. Legume cover crops are an alternative N source that can reduce agricultural N2O emissions compared to fertilizer N. However, our understanding of episodic N2O flux following cover crop incorporation by tillage is limited and has focused on single-species cover crops. Our study explores whether increasing cover crop functional diversity with a legume–grass mixture can reduce pulse emissions of N2O following tillage. In a field experiment, we planted crimson clover (Trifolium incarnatum L.), cereal rye (Secale cereal L.), a clover–rye mixture, and a no-cover control at two field sites with contrasting soil fertility properties in Michigan. We hypothesized that N2O flux following tillage of the cover crops would be lower in the mixture and rye compared to the clover treatment because rye litter can decrease N mineralization rates. We measured N2O for approximately 2 weeks following tillage to capture the first peak in N2O emissions in each site. Across cover crop treatments, the higher-fertility site, CF, had greater cover crop biomass, 2-fold-higher aboveground biomass N, and higher cumulative N2O emissions than the lower-fertility site, KBS (413.4±67.5 vs. 230.8±42.5 g N2O-N ha−1; P=0.004). There was a significant treatment effect on daily emissions at both sites. At CF, N2O fluxes were higher following clover than the control 6 d after tillage. At KBS, fluxes from the mixture were higher than rye 8 and 11 d after tillage. When controlling for soil fertility differences between sites, clover and mixture led to approximately 2-fold-higher N2O emissions compared to rye and fallow treatments. We found partial support for our hypothesis that N2O would be lower following incorporation of the mixture than clover. However, treatment patterns differed by site, suggesting that interactions between cover crop functional types and background soil fertility influence N2O emissions during cover crop decomposition.

In the Search for Novel, Isoflavone-Rich Functional Foods-Comparative Studies of Four Clover Species Sprouts and Their Chemopreventive Potential for Breast and Prostate Cancer.

Despite a significant amount of research, the relationship between a diet rich in isoflavones and breast and prostate cancer risk is still ambiguous. The purpose of the current study was to pre-select the potential candidate for functional foods among red, white, crimson, and Persian clover sprouts, cultured for different periods of time (up to 10 days), with respect to the isoflavone content (determined by HPLC-UV-VIS), and to verify their impact on hormone-dependent cancers in vitro. The red clover sprouts were the richest in isoflavones (up to 426.2 mg/100 g dw), whereas the lowest content was observed for the crimson clover. Each species produced isoflavones in different patterns, which refer to the germination time. Hormone-insensitive MDA-MB-231 breast cancer cells were more resistant to the tested extracts than estrogen-dependent MCF7 breast cancer cells. Regarding prostate cancer, androgen-dependent LNCap cells were most susceptible to the tested sprouts, followed by androgen-insensitive, high metastatic PC3, and low metastatic DU145 cells. The observed cytotoxic impact of the tested sprouts is not associated with isoflavone content, as confirmed by chemometric analysis. Furthermore, the sprouts tested revealed a high antioxidant potential, and were characterized by high safety for normal breast and prostate cells.

Forage Yield, Quality, and Impact on Subsequent Cash Crop of Cover Crops in an Integrated Forage/Row Crop System

Dual-use cover crops as forage for livestock could offer ecological and economic benefits when incorporated into rotations with corn (Zea mays L.) and soybean (Glycine max (L.) Merr) in the Mid-South USA; however, information on implementation and impact is limited. A factorial of sixteen cool-season species and a no-cover control by two management systems (forage harvest and residue left in the field) was repeated under two cover crop planting/termination timings: long-season (Oct. through May; corn/cover-crop/soybean) and short-season (Nov. through Apr.; soybean/cover-crop/corn), two locations (Spring Hill and Knoxville, TN), and two growing seasons (2017/2018 and 2018/2019). Data were analyzed using a mixed model ANOVA (SAS 9.4.). The forage biomass did not differ by species within the short-season (415 to 1583 kg ha−1) but did in the long-season (475 to 4282 kg ha−1). Within the long-season, crimson clover (Trifolium incarnatum L.) and winter pea (Pisum sativum subsp. arvense (L.)) had crude protein and acid detergent fiber values within the range for prime forage and were among the highest biomasses. The forage harvest did not negatively affect soil properties or succeeding crop yield and quality. If appropriate species are selected, cover crops within a corn/cover-crop/soybean rotation can provide quality forage, without reducing the short term ecological benefits.

Legume cover crop type and termination method effects on labile soil carbon and nitrogen and aggregation

AbstractGrowers use cover crops to provide nutrients for crops and build soil organic matter (SOM). Termination methods may alter the effects of cover crops on soil labile C and N. We examined how two cover crops and three termination methods affected soil microbes, soil aggregates, and C and N pools in an organic grain system. We compared crimson clover (Trifolium incarnatum L.) (CC), hairy vetch (Vicia villosa Roth) (HV), and a control together with disking, mowing, or a roller‐crimper for effects on hot‐water‐extractable carbohydrates, microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN), potentially mineralizable C and N, and aggregation (quantified by mean weight diameter [MWD]). Disking comprised flail mowing plots and then cultivating. Roller‐crimping occurred via a roller with blades. Vetch soil contained 14% higher MBC than no cover crop pretermination, possibly because of enhanced rhizodeposition. Planting CC resulted in 44% higher MBC than no cover crop a week after termination, likely due to its higher biomass C/N ratio. Disking decreased MWD relative to flail mowing in no cover crop soils at 4 wk after termination across both years at 0‐to‐5‐cm depth. In addition, MWD was lower under CC than under no cover crop for both the flail mowed and roller‐crimped treatments at 4 wk after termination across both years from 0 to 5 cm. This is possibly due to enhanced desiccation of the soil in bare plots after termination. Our results indicate that quantity and quality of biomass of different legume species, rather than termination methods, dominated effects on labile C.

Fall cover crop nitrogen uptake drives reductions in winter-spring leaching.

Cover crops can reduce nitrate leaching after cash crop harvest. Despite widespread cover crop implementation, there has been a limited effect on water quality in the Chesapeake Bay watershed. We hypothesize that typical timing for Maryland cover crop planting after cash crop harvest is too late to allow roots to take up substantial nitrate from the soil profile before it is leached by winter drainage water. Across four site-years (including sandy and silty soils), we compared various planting dates for a radish (Raphanus sativus L.)-crimson clover (Trifolium incarnatum L.)-triticale (Triticosecale) cover crop mixture. Also, across two site-years we compared early-planted pure rye, radish, and a three-species mixture with no cover. We measured cover crop biomass and N content and used tension lysimeters to measure deep soil porewater nitrate concentrations. Cumulative nitrate leaching was calculated from these concentrations and weather-based drainage estimates. Cover crops were planted on four dates over a 6-wk period. Overall, cover crops planted first, second, third, fourth, and no cover crop (just weeds) resulted in 3,340, 3,160, 1,600, 303, and 164kg ha-1 of biomass; biomass N accumulation of 65.5, 68.6, 44.0, 9.88, and 4.79kg N ha-1 ; and mean porewater concentrations of 2.71, 2.57, 4.72, 10.0, 17.1mg L-1 of nitrate-N, respectively. Over two site-years, the three-species mix performed as well or better than pure rye or radish. Early planting altered cover crop species proportions, increased cover crop productivity, and reduced nitrate leaching from agricultural fields.

Assessing Direct and Residual Effects of Cover Crops on the Soybean Cyst Nematode, Heterodera glycines.

Greenhouse experiments were conducted to determine if cover crops directly decrease population densities of the soybean cyst nematode (SCN), Heterodera glycines, and/or have residual effects on reproduction of the nematode on soybean (Glycine max). Population densities of SCN were not significantly decreased by nine cover crop plants or three cover crop mixes compared with a non-planted soil control in a repeated 60-day-long greenhouse experiment. When susceptible soybeans were grown in the soils after cover crop growth, fewer SCN females formed after three annual ryegrass (Lolium multiflorum) cultivars (Bounty, King, and RootMax), the Daikon radish (Raphanus sativus var. longipinnatus) cultivar CCS779, Kodiak mustard (Brassica juncea), and a mix containing cereal rye, crimson clover (Trifolium incarnatum), plus Daikon radish (cultivars not stated) compared with following the non-planted control. In another repeated experiment, cover crops were grown for 56 days in SCN-infested soil in the greenhouse then exposed to Iowa winter conditions for 28 days to simulate winter termination of the plants. One treatment, a cover crop mix containing 'Bounty' annual ryegrass plus 'Enricher' Daikon radish, had a decrease in SCN population density greater than the non-planted control at the end of the experiment. Significantly fewer SCN females formed on soybeans grown after several cover crops, including the three annual ryegrass cultivars that had the suppressive residual effects in the first experiment. In summary, there were no cover crop treatments that consistently decreased SCN population densities across experiments, and only one cover crop treatment in one experiment significantly reduced SCN population densities more than a non-planted soil control. However, there was a somewhat consistent, adverse, residual effect of cover crops on reproduction of SCN on susceptible soybeans after growth of multiple cover crops.

Effects of cover crops on soil hydraulic properties during commodity crop growing season

AbstractCover crops (CCs) can improve soil hydraulic properties prior to termination, but their effects on soil hydraulic properties during the growing season are less known. The objective of this study was to investigate the influence of no‐till CC on the soil hydraulic properties during the commodity crop growing season in Murfreesboro, USA. The CCs included hairy vetch (Vicia villosa Roth.), crimson clover (Trifolium incarnatum L.), winter wheat (Triticum aestivum L.), winter peas (Lathyrus hirsutus L.), oats (Avena sativa), triticale (Triticale hexaploide Lart.), barley (Hordeum vulgare L.) and flax (Linum usitatissimum L.). The cash crop grown was corn (Zea mays). Soil samples were collected using a cylindrical core (55 mm inside diameter, 60 mm long) at 0–10, 10–20, and 20–30 cm depths during April (prior to CC termination), May, June and July. Results showed that soil bulk density (Db) was 23%, 12%, 11% and 10% higher under no cover crop (NCC) compared with CC management during April – July, respectively. This suggests a lower rate of soil consolidation under CC management even after several rainfall events. Four months after CC termination, macroporosity and total porosity were 306 and 50% higher, respectively, under CC compared with NCC management. Therefore, saturated hydraulic conductivity (Ksat) during July was two times higher under CC management compared with NCC management and this can affect increase water infiltration and conservation during the growing season. Due to CC root‐induced improvement in macroporosity, CCs had 64% higher volumetric water content (θ) at saturation during July compared with NCC management. Cover crops can improve soil hydraulic properties and these benefits can persist for up to four months after termination.

In situ water infiltration: Influence of cover crops after growth termination

AbstractCover crops (CCs) are known to influence water infiltration just prior to termination, but their effects on water infiltration over time are less known. This study investigated the influence of CCs on in situ water infiltration just prior to CC termination (during April) and again 2 mo after CC termination (during June). The multi‐species mixture of CCs used included hairy vetch (Vicia villosa Roth.), crimson clover (Trifolium incarnatum L.), winter wheat (Triticum aestivum L.), winter peas (Lathyrus hirsutus L.), oats (Avena sativa L.), triticale (Triticale hexaploide Lart.), barley (Hordeum vulgare L.), and flax (Linum usitatissimum L.). Infiltration rates were measured using double‐ring infiltrometers during April and June. The physically based Parlange and Green‐Ampt models were fitted to measured infiltration data. Cumulative infiltration was 52% higher in April and 68% higher in June under CC compared with no cover crop (NC) management. During April, the Parlange model–estimated saturated hydraulic conductivity parameter (Kdr) was 245% higher under CC compared with NC management. During the same sample period, the Green‐Ampt–estimated Kdr parameter was 383% higher under CC compared with NC management. The higher sorptivity parameter and lower antecedent water content under CC compared with NC management during both measurement periods suggest that CCs can significantly improve water infiltration into the soil, and this effect can last for up to 2 mo after CC termination.

102 Effects of Cattle Removal Date on Forage Production and Steer Performance in Grazed Cover Crops

Abstract Grazing of cool-season cover crops has been shown to be a viable tool in extending the grazing season while mitigating environmental risks associated with row crop farming systems. Grazing cover crops is not novel, but most information available on this practice focuses on soil health as opposed to forage production and animal performance. The objective was to evaluate the effects of cattle removal date on steer performance, forage yield, and forage quality. Twelve 1.2-ha pastures were established in a forage mix consisting of ‘Cosaque’ oats (Avena strigose), ‘FL401’ cereal rye (Secale cereale), ‘AU Sunrise’ crimson clover (Trifolium incarnatum), and ‘T-raptor’ brassica (Brassica napus ×B. rapa) and randomly allocated to be grazed through either mid-February (FEB), mid-March (MAR), or mid-April (APR) with an un-grazed control (CON). Three tester steers were randomly placed in each paddock with the exception of CON and allowed ad libitum grazing. Animals were weighed every 30 d for determination of average daily gain (ADG). Forage was harvested bi-weekly and analyzed for average yield, NDF, ADF, and CP. All data were analyzed using MIXED procedure of SAS version 9.4 (SAS Inst., Cary, NC). The following data represents the first three years of a four-year project. Differences in yield were detected between CON and FEB (3,913 vs. 2,398 kg/ha; P < 0.001), CON and MAR (3,913 vs. 1,908 kg/ha; P < 0.001), and CON and APR (3,913 vs. 2,126 kg/ha; P < 0.001). A difference in CP was detected between MAR and CON (13.36% vs. 11.78%; P < 0.02). No differences were detected for ADG (1.2 kg/day, P = 0.56), NDF (52.48%, P = 0.99), or ADF (30.82%, P = 0.4) among treatments. These results indicate that grazing will reduce forage yield, but removal date of cattle will not further affect forage yield or steer average daily gain.

34 Extended Effects of Sequential Weaning and Backgrounding Management in Beef Calves

Abstract Alternate weaning methods and backgrounding periods are strategies to reduce calf morbidity and mortality at feedlot arrival. The objective of this study was to assess the collective effects of weaning and post-weaning management practices on potential carryover effects on calf health and performance through the backgrounding phase. A total of 216 steer calves (average BW, 298 kg) from three Auburn University research farms were randomly assigned to one of three different weaning method groups: Fenceline weaning, nose-flap weaning, or abrupt weaning. Calves were weighed on d 0 and d 14 post weaning, and then began a 60-d preconditioning period. Calves were randomized according to previous weaning management, farm of origin, and body weight to one of three nutritional management strategies in a 3 ×3 factorial design: cool-season baleage (oats, ryegrass and crimson clover) and 1% BW dried distillers grains (DDGS), bermudagrass hay and 1% BW DDGS, or grazing mixed warm-season annuals and 1% BW DDGS. Calf body weights were collected on d 0, d 30 and d 60 of the backgrounding phase. Weights did not differ during the weaning phase but calves in the fenceline group had the greatest average daily gain (1.13 kg/d; P < 0.0001) during this phase. There was a weaning × backgrounding treatment interaction (P = 0.0097) for average daily gain during the first 30 d of the backgrounding phase. Calves that were fenceline weaned and on the cool season baleage diet had the highest average gain at 1.02 kg/d, whereas abruptly weaned calves on the grazing diet only gained 0.29 kg/d in the first 30 d. Steers on the cool season baleage diet had the greatest total gain (P < 0.0001) at 45.8 kg over the course of the 60-d period. These results indicate that backgrounding diet, coupled with weaning management strategies, may influence calf performance during the transition period for calves into the post-weaning phase.

Winter legume cover effects on yields of biomass‐sorghum and cotton in Georgia

AbstractAmong the many ecosystems services of winter covers, winter legumes have an advantage over winter grain covers by fixing N that may be used by subsequent crops. A 5‐yr study was conducted to compare the biomass yields of five leguminous winter cover crops [Austrian winter pea (Pisum sativum L.), fava bean (Vicia fava L.), narrow‐leaf lupin (Lupinus angustifolius L.), cahaba vetch (Vicia spp.), crimson clover (Trifolium incarnatum L.)] plus rye (Secale cereale L.) and determine the effects of these winter cover crops either harvested or left on the soil on subsequent biomass sorghum [Sorghum bicolor (L.) Moench] and cotton (Gossypium hirsutum L.) yields at two field locations in Georgia. Lupin produced between 4.16 and 9.54 Mg ha−1 biomass, approximately two to four times more than any other cover at both locations every year. Lupin, followed by vetch and winter pea had the greatest positive effect on biomass sorghum yields. Biomass‐sorghum yields after lupin cover were not significantly different whether biomass was retained on the soil by rolling or removed. Seed cotton yields were higher after lupin and vetch . Significantly higher sorghum and cotton yields occurred for rolled covers with crimson clover, winter pea, and fava bean. Averaged over the years and locations, lupin biomass produced approximately 143 kg ha−1 N, more than any other cover. The study suggests that harvested or grazed lupin or vetch covers could give similar benefits to summer row crops compared with traditionally leaving the cover on the soil.

Solanum linnaeanum Leaves: Chemical Profiling of VOCs and Effects on Seed Germination and Early Growth of Monocots and Dicots.

Some Solanaceae plants are a rich source of sesquiterpenoid phytoalexins with allelopathic potential. Powder and aqueous extract obtained from the leaves of Solanum linnaeanum Hepper & P.M.L. Jaeger were used to treat the seeds of three target species (Lolium multiflorum Lam., Sinapis alba L. and Trifolium incarnatum L.). Both matrices were evaluated along with untreated controls to determine their toxicity on germination and seedling growth. The results revealed that the pre-emergence treatments were able to be very effective against all three species in the filter paper test by inhibiting the germination up to 100 %. The effectiveness was reduced by the interaction with soil. Despite this, significant data were obtained, albeit different according to the applied matrix. In general, L. multiflorum was the most sensitive to both the action of the leaf powder and aqueous extract while S. alba was found to be the most resistant to powder activity and T. incarnatum had the strongest response to the extract. For the first time, SPME-GC/MS technique was used to characterize the volatile chemical profile of S. linnaeanum leaves. The analyses highlighted the presence of different classes of compounds including terpenoids and sesquiterpenoids potentially useful in the fight against noxious plants both in natural and cultivated ecosystems.

Integrated environmental and economic assessments of producing energy crops with cover crops for simultaneous use as biofuel feedstocks and animal fodder

Energy crops grown on marginal lands offer an alternative supply of renewable resources while avoiding competition with food crops and supporting feed crops. To sustainably grow energy crops, the economic and environmental impacts of various crop management practices such as the adoption of cover crops, fertilization rates, harvesting methods and its end use applications for animal feed or biofuels should be investigated. In this study, we investigated the life cycle analysis (LCA) and economic evaluation of growing two energy crops (energy cane, and napier grass) on the marginal lands with three fertilizer treatments (0, 100, and 200 kg N ha⁻¹), and with a cover crop (clover, Trifolium incarnatum L) in the southeastern United States (US). Energy crop was harvested once a year in the late fall for biofuel applications, while the Napier grass was harvested twice a year: first harvested early in spring for animal feed and later harvested in the fall for biofuel application. Experimental field data such as biomass yield, crop management practices, farm inputs, and carbon stored in the soil, were determined to assess the global warming potential and the delivered cost of each energy crop. Napier grass had lower global warming (GW) impacts and biomass delivery costs, 34–153 kg CO₂ eq. per oven-dry metric ton (ODMT) and $51–$57 perODMT, respectively than that of energy cane. However, both the energy crops provided carbon sequestrations (−17 and −232 kg CO₂ eq. ODMT⁻¹) and thus net GW impact varied between 51 and (−14) kg CO₂ eq. ODMT⁻¹ based on the treatments. When the napier grass was harvested for both biofuel and fodder applications, the overall GW impacts and the delivered costs were reduced. Therefore, energy crops can be grown in marginal lands for increased carbon sequestration while reducing the GW impacts of energy crops for biofuel production. The integrated environmental and economic analyzes further demonstrated that the energy crop delivered costs and GW impacts could be further reduced, if the energy crops can be utilized for both biofuel and feed applications.

Chemical volatile composition and phytotoxic potential of Daphne gnidium L. leaves

Daphne gnidium L. (Thymelaeaceae) is an evergreen shrub from the Mediterranean area traditionally used for its medicinal and non-medicinal properties. Several studies showed its adverse impact on different targets including malignant cells, microbes, radicals, insects. The negative interactions between D. gnidium and other plant species have been rather neglected so far, as well as its chemical volatile composition. Therefore, this work aimed to assess the phytotoxic activity of D. gnidium on filter paper and soil in pre-emergence conditions by testing both the aqueous extract (10–100%) and the powder (0.25–1 g) obtained from the leaves as bioagrochemicals. The results showed that D. gnidium was able to significantly decrease seed germination and growth parameters of the receiver plants with different effectiveness (p-values < 0.05). Overall, Sinapis alba L. (Brassicaceae) was the most susceptible species followed by Lolium multiflorum Lam. (Poaceae) and Trifolium incarnatum L. (Fabaceae) while aqueous extract was more active than the powder. Solid-Phase Microextraction (SPME) sampling technique and Gas Chromatograph/Mass spectrometer (GC/MS) analyses were used to characterize the volatile fraction highlighting considerable differences in the composition of the analyzed samples. Hexahydrofarnesyl acetone (29.7%) followed by 3,7,11,15-tetramethyl-2-hexadecen-1-ol (28.3%) and β-damascenone (32.0%) followed by eudesma-1,4(15), 11-triene (27.1%) were detected as main volatile compounds of the powder and the aqueous extract, respectively.

Cover crops can increase ammonia volatilization and reduce the efficacy of urease inhibitors

AbstractSurface application of urea can result in high nitrogen (N) losses through ammonia (NH3) volatilization. While management practices aim to increase the efficiency of nutrient cycling and prevent N loss, it is unknown whether the combination of multiple practices will have a synergistic or antagonistic effect. Therefore, laboratory volatilization studies were conducted to determine the effect of five cover crop treatments (surface clover [Trifolium incarnatum L.] and rye [Secale cereale L.], incorporated clover and rye, and bare soil), three N application timings (2, 4, and 8 wk after cover crop addition), and two N sources (untreated and treated urea) on the effectiveness of a urease inhibitor. Soils were incubated according to N application timing treatment, amended with the appropriate N source, and placed in chambers which captured NH3 over 7 d. There were significant interactions between cover crop treatment and N source and N source and N application timing on cumulative NH3 loss, ranging from 29 to 174 kg N ha−1. Losses were highest from treated urea when applied 2 wk after residue addition (75.9 kg N ha−1) or on top of surface residues (85.8 kg N ha−1). There was no significant effect of application timing on cumulative NH3 loss from untreated urea. However, inhibitor effectiveness did increase when residue was applied eight weeks after residue addition (77%) as compared with 2 wk after residue addition (45%). Future research should focus on alternate dosing or application timing to overcome high residue scenarios in these systems.

Cover crop usage for the sustainable management of soilborne diseases in woody ornamental nursery production system

Cover crops represent a potential tool for suppression of soil borne diseases in woody ornamental nursery production, which can cause significant economic losses. Field experiments were conducted in 2019 and 2020 to explore the effects of a cover crop and the timing of cover crop disturbance on soilborne disease suppression. Soils from red maple (Acer rubrum ‘October Glory’) plantations grown with or without a cover crop [crimson clover (Trifolium incarnatum)] were sampled following senescence of the cover crop. Greenhouse bioassays were conducted using red maple cuttings on inoculated (with Rhizoctonia solani, Phytopythium vexans or Phytophthora nicotianae) and non-inoculated field soils. Plant height, total and root fresh weight were measured, and the roots were assessed for disease severity on a 0 to 100% root damage scale. Pathogen recovery was assessed by culturing root pieces (~1 cm length) on oomycetes or Rhizoctonia semi-selective media. Soil samples were analyzed for organic matter, nitrogen, phosphorus, potassium, pH and Pseudomonad population count. A minimal effect of cover crop disturbance timing (late fall or early spring) was found on disease suppression. Cover crop usage reduced disease severity and pathogen recovery in red maple field soils. Plants grown in cover cropped soil had greater total, root and aboveground fresh weight compared with those from non-cover cropped soil, but plant height was not affected. Cover crops increased soil organic matter and total nitrogen in 2020. Pseudomonad populations were higher when cover crops were used. The results suggest that cover crops can reduce soilborne disease in woody ornamentals.

Effectiveness of Cover Crop Termination Methods on No-Till Cantaloupe

In a no-till system, there are many different methods available for terminating cover crops. Mechanical termination, utilizing rolling and crimping technology, is one method that injures the plant without cutting the stems. Another popular and commercially available method is mowing, but this can cause problems with cover crop re-growth and loose residue interfering with the planter during cash crop planting. A field experiment was conducted over three growing seasons in northern Alabama to determine the effects of different cover crops and termination methods on cantaloupe yield in a no-till system. Crimson clover, cereal rye, and hairy vetch cover crops were terminated using two different roller-crimpers, including a two-stage roller-crimper for four-wheel tractors and a powered roller-crimper for a two-wheel walk-behind tractor. Cover crop termination rates were evaluated one, two, and three weeks after termination. Three weeks after rolling, a higher termination rate was found for flail mowing (92%) compared to lower termination rates for a two-stage roller (86%) and powered roller-crimper (85%), while the control termination rate was only 49%. There were no significant differences in cantaloupe yield among the rolling treatments, which averaged 38,666 kg ha−1. However, yields were higher for cereal rye and hairy vetch cover crops (41,785 kg ha−1 and 42,000 kg ha−1) compared to crimson clover (32,213 kg ha−1).

Agricultural Greenhouse Gas Fluxes Under Different Cover Crop Systems

Cultivated lands that support high productivity have the potential to produce a large amount of GHG emissions, including carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). Intensive land management practices can stimulate CO2, N2O, and CH4 emissions from the soil. Cover crop establishment is considered as one of the sustainable land management strategies under warm and humid environmental conditions. To better understand how the incorporation of cover crops affect three major GHGs, we compared trace gas fluxes in a no-till maize field over the whole growing season in 2018 in a no cover crop (Tr) system and three cover crop systems: crimson clover (CC), cereal rye (CR), and living mulch (LM) using white clover. In 2019, we further explored potential differences in the three GHGs between in-row (IR) and between-row (BWR) of maize for LM and Tr systems during the early growing season. Measurements were taken using a cavity ring-down spectroscopy gas analyzer in Watkinsville, GA. In 2018, the highest CO2 flux (7.00 μmol m−2 s−1) was observed from BWR of maize for LM. The maximum N2O flux observed in LM on June 20th in 2018 was when soil N increase rate was the largest. Soils served as sinks for CH4 and Tr system served as the smallest CH4 sink compared to the other three cover crop systems. For N2O, the highest fluxes were observed from the TrIR plot (4.13 μmol m−2 hr−1) in 2019 with the greatest N inputs. In 2019, we observed a smaller CH4 sink in TrIR (−0.13 μmol m−2 hr−1) compared to TrBWR (−0.67 μmol m−2 hr−1) due potentially to greater NH4+ inhibition effects on CH4 consumption from greater N fertilizer inputs. The net carbon equivalent (CE) from May 23rd to Aug 16th in 2018, taking into account the three GHG fluxes, soil carbon content, and fertilizer, irrigation, and herbicide application, were 32–97, 35–101, 63–139, and 40–106 kg ha−1 yr−1 for CC, CR, LM, and Tr, respectively. LM had the lowest net CE after removing white clover respiration (−16–60 kg ha−1 yr−1). Our results show that implementing different types of cover crop systems and especially the LM system have some potential to mitigate climate change.

Working collection of crimson clover (Trifolium incarnatum L.) in the Ciscarpathia

Aim. To identify collection accessions – sources of valuable traits for using as starting material to create varieties of perennial grasses in Western Ukraine. Results and Discussion. The vegetable protein problem is one of the main issues facing scientists whose activities are related to agriculture, ecology and other areas of biology. The Ciscarpathia is a zone of natural meadows, hayfields and pastures, where a large number of plant species belonging to different botanical families grow. Among the natural vegetation on pastures, meadows and fallows, clover species are most often found. Trifolium incarnatum L. is an annual winter-spring plant. It is widely used in agriculture as a nitrogen-fixing cover crop. The crimson clover collection comprises 24 accessions. Some promising accessions that can be used as starting material in breeding for high productivity (green mass, hay and seeds), herbage capacity, resistance to diseases and pests were selected. Reference accessions and sources of economically valuable traits, which are actively involved in breeding, were singled out. During the study (2019-2021), accessions were investigated in detail for biological and morphological features. We evaluated the crimson clover collection for germinability, winter survival, flowering time, green mass per plant, and seed yield. The results showed that the crimson clover collection could be tentatively divided into 3 groups: early-ripening (70-79 days; 37.5%), mid-ripening (83-87 days; 50.0%) and late-ripening (92-94 days; 12.5%). Nine accessions (PFZ 00625, PFZ 02148, PFZ 01264, PFZ 01266, PFZ 01295, PFZ 01273, PFZ 01270, PFZ 02266, and PFZ 02265) ripened slightly earlier. They are potential parents to develop an early-ripening population. Three accessions (PFZ 02268, PFZ 02267, and PFZ 02073) ripened significantly later than all the others. Thus, these accessions are excellent candidates to develop a late-ripening population. Depending on the region and cultivation system, farmers may be interested in both early-ripening and late-ripening crimson clover. Conclusions. Literature review allowed us to note that the studied crimson clover accessions had several advantages when used in production, namely: they are annuals, have high vegetation rates and productive potentials. Crimson clover accessions showed particularly distinct differences in autumn emergence and flowering time, indicating greater diversity and potential for breeding. In contrast, winter survival, green mass per plant showed greater intra- and inter-year variations. Autumn emergence and winter survival were found to be positively correlated, and both traits were negatively correlated with green mass per plant. Some accessions were identified as highly effective in several key traits and are of particular interest as parents in further breeding: PFZ 02118, PFZ 01270, PFZ 02267, PFZ 02073, PFZ 02072, PFZ 01290.