Cover Crop Treatments Research Articles

Effects of Fall and Winter Cover Crops on Weed Suppression in the United States: A Meta-Analysis

Cover cropping recently emerged as a promising alternative to conventional tillage and herbicide use for weed suppression in agricultural systems. We investigated their effectiveness in weed control and the varying effects of different management strategies using a meta-analysis. Our analysis studied two categories: weed biomass control and weed density control. We employed a random-effect model to analyze weed biomass to address between-study heterogeneity and found that cover crop treatments led to a significant 62.6% reduction in weed biomass. These results are robust to outliers and publication bias. Furthermore, subgroup analysis found that planting a mixture of cover crop types was more effective than planting a single type. Additionally, planting a mixture of cover crop species, which are subcategories of cover crop types, was found to be more effective than planting a single species. Our analysis also unveiled a persistent, albeit diminishing, reduction in weed biomass even after the termination of cover crops. For weed density analysis, we used a fixed-effect model due to the absence of between-study heterogeneity and found a statistically significant reduction (45.4%) in weed density. Subgroup analysis revealed no significant difference in weed density control between legume and grass cover crop types.

Cover crop residue decomposition triggered soil oxygen depletion and promoted nitrous oxide emissions

Cover cropping is a promising strategy to improve soil health, but it may also trigger greenhouse gas emissions, especially nitrous oxide (N2O). Beyond nitrogen (N) availability, cover crop residue decomposition may accelerate heterotrophic respiration to limit soil O2 availability, hence promote N2O emissions from denitrification under sub-optimal water-filled pore space (WFPS) conditions that are typically not conducive to large N2O production. We conducted a 21-day incubation experiment to examine the effects of contrasting cover crop residue (grass vs legume) decomposition on soil O2 and biogeochemical changes to influence N2O and CO2 emissions from 15N labeled fertilized soils under 50% and 80% WFPS levels. Irrespective of cover crop type, mixing cover crop residue with N fertilizer resulted in high cumulative N2O emissions under both WFPS conditions. In the absence of cover crop residues, the N fertilizer effect of N2O was only realized under 80% WFPS, whereas it was comparable to the control under 50% WFPS. The N2O peaks under 50% WFPS coincided with soil O2 depletion and concomitant high CO2 emissions when cover crop residues were mixed with N fertilizer. While N fertilizer largely contributed to the total N2O emissions from the cover crop treatments, soil organic matter and/or cover crop residue derived N2O had a greater contribution under 50% than 80% WFPS. Our results underscore the importance of N2O emissions from cover crop-based fertilized systems under relatively lower WFPS via a mechanism of respiration-induced anoxia and highlight potential risks of underestimating N2O emissions under sole reliance on WFPS.

How Do Mixed Cover Crops (White Mustard + Oats) Contribute to Labile Carbon Pools in an Organic Cropping System in Serbia?

Sustainable farming is one of the priority goals of the "4 per 1000" concept with regard to the preservation of soil fertility and carbon sequestration. This paper presents a study on the use of a mixture of cover crops of self-grown oats (Avena sativa L.) and sown white mustard (Sinapis alba L.) in organic farming under the agroecological conditions of Serbia. The main objective was to identify sensitive carbon pools (microbial carbon and nitrogen, basal respiration and a number of specific groups of soil microorganisms) in organic farming with and without cover crops. The inclusion of a mixture of white mustard and self-grown oats as a cover crop led to a significantly increased biogenity of the soil compared to a control after only a few years of investigation. The number of microorganisms, soil respiration and microbial biomass carbon were significantly higher in the cover crop treatment compared to the control soil on an organic farm in Serbia. This is the first study in Serbia to investigate the effect of self-grown oats as a cover crop. Further research will incorporate a wider range of variables and factors in order to develop a sustainable and effective site-specific system for organic crop production in Serbia.

Timing Termination of a Biofumigant Cover Crop for Weed Suppression in Chile Pepper

Overwinter mustard cover crops incorporated into soil may suppress early-season weeds in chile pepper (Capsicum annuum). However, the potential for mustard cover crops to harbor beet leafhoppers (Circulifer tenellus) is a concern because beet leafhoppers transmit beet curly top virus to chile pepper. The objectives of this study were to determine the amounts of a biopesticidal compound (sinigrin) added to soil from ‘Caliente Rojo’ brown mustard (Brassica juncea) cover crops ended on three different days before beet leafhopper flights during spring and to determine the effects of the cover crop termination date on weed densities and hand-hoeing times for chile pepper. To address these objectives, a field study was conducted in southern New Mexico. In 2019–20, the cover crop was ended and incorporated into soil 45, 31, and 17 days before beet leafhopper flights. In 2020–21, cover crop termination occurred 36, 22, and 8 days before beet leafhopper flights. Treatments also included a no cover crop control. Cover crop biomass and sinigrin concentrations were determined at each termination. Chile pepper was seeded 28 days after the third termination date. Weed densities and hand-hoeing times were determined 28 and 56 days after chile pepper seeding. In 2019–20, the third termination (17 days before beet leafhopper flights) yielded the maximum cover crop biomass (820 g⋅m−2) and greatest sinigrin addition to soil (274 mmol⋅m−2). However, only the second termination (31 days before beet leafhopper flights) suppressed weeds in chile pepper. In 2020–21, the third termination (8 days before beet leafhopper flights) yielded the maximum cover crop biomass (591 g⋅m−2) and greatest sinigrin addition to soil (213 mmol⋅m−2), and it was the only treatment that suppressed weeds. No cover crop treatment reduced hand-hoeing times. These results indicate that overwinter mustard cover crops can be ended to evade beet leafhopper flights and suppress weeds in chile pepper.

Influence of the Long-Term Application of Management Practices (Tillage, Cover Crop and Glyphosate) on Greenhouse Gas Emissions and Soil Physical Properties

Soil treatments have a significant influence on the agricultural and environmental productivity of agricultural practices. Arable lands are one of the sources of greenhouse gas emissions (GHG) that are influenced by the chemical and physical properties of the soil and are an essential contributor to climate change. We aim to evaluate the long-term management of agricultural practices, such as different tillage systems, cover crops, and glyphosate, on GHG emissions and soil physical properties. The field trial involved three tillage systems (conventional tillage (CT), reduced tillage (RT), and no-tillage (NT)), along with variations in cover cropping (with and without cover crops) and glyphosate application (with and without glyphosate). These treatments were implemented during the cultivation of oilseed rape in 2022 as part of a cropping sequence consisting of five crops: winter wheat; winter oilseed rape; spring wheat; spring barley; and field pea. Greenhouse gas emissions (carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)) were directly measured using a closed static chamber system. Through the examination of these management techniques, the soil’s physical properties over the studied period were assessed for their impact on GHG fluxes. The findings of the study reveal that N2O emissions were relatively low during the first month of measurement, with significant differences (p < 0.05) observed in the interaction between cover crop and glyphosate treatments. Additionally, N2O emissions were notably elevated in the reduced (0.079 µg m−2 h−1) and conventional tillage (0.097 µg m−2 h−1) treatments at the second month of measurement. Regarding CH4, increased emissions were observed in the reduced tillage and cover crop treatments. CO2 emissions exhibited variability across all of the investigated treatments. Notably, GHG fluxes spiked at the second measurement, signifying the maximum uptake of nutrients by the main plants during the growth phase. Greenhouse gas emissions leveled off across all of the treatments following the harvest, marking the end of the cultivation period. The influence of the deployed techniques varied across the determined physical parameters of the soil. The incorporation of cover crops contributed to improved water content and, further, to electrical conductivity. Glyphosate use showed no direct impact on physical properties of the soil while the different tillage treatments had varying effects on the distribution of the physical properties of the soil with respect to the degree of disturbance or tillage-induced changes. Additionally, GHG emissions were strongly correlated with precipitation at one week and two weeks before sampling, except for CO2, which showed a weaker correlation at two weeks before GHG sampling. The findings indicate that reduced and conventional tillage methods might adversely affect greenhouse gas emissions and plant functionality, particularly concerning nutrient release and uptake, especially in temperate climate conditions.

Effects of cultural practices on weed community and seedbank dynamics in a potato rotation

ContextStagnant yields and declining soil health are common characteristics of high-intensity, low-residue cropping systems, such as potato, particularly in northeastern North America. Incorporating cultural practices including cover cropping and manure application is a way to combat declines in agroecosystem health and potato productivity. However, manure application and the use of cover crops may exacerbate weed issues through seedbank additions. ObjectiveThis study was aimed at investigating how the cultural practices of cover cropping and manure application and their associated management activities can alter weed community dynamics and weed seedbank composition in a northeastern North American potato rotation. MethodsThe study evaluated the use of eight cover crop mixtures—annual and perennial grasses and legumes—grown over two years with/without manure added in year one of the rotation. It also examined the effects of the cover crop mixtures and the presence/absence of manure on the weed community and on seedbank dynamics within a three-year potato rotation between 2019 and 2021. ResultsIn year one of the study and directly after application, manure plots had greater weed seedbank density and species richness; however, this did not result in greater in-season weed biomass. Manure application resulted in a gradual decline in weed seedbank density over time regardless of cover crop treatment. Further, manure application increased the in-season competitive ability of cover crops, resulting in greater weed suppression per unit of cover crop biomass. In contrast, in the absence of manure, weed seedbank density remained largely unchanged through time regardless of cover crop treatment. We found that management practices associated with annual and perennial cover crops had distinct ecological filtering effects throughout the rotation on the weed community and prevented the dominance of any particular species. ConclusionTogether, our results demonstrate that combining the cultural practices of annual or perennial cover cropping and manure application contributes to weed suppression and should be considered an important component of sustainable potato production.

Soil Ecoenzymatic Stoichiometry Reveals Microbial Metabolic Limitations in Apple Orchards with Cover Crop and Organic Fertilizer Incorporation

Understanding the stoichiometry of extracellular enzymes in soil, particularly in relation to nutrient acquisition (e.g., carbon, nitrogen, phosphorus), provides valuable insights into microorganisms’ resource requirements. This study investigates the metabolic constraints of soil microorganisms in response to different growth stages of apple trees under various soil management practices. A 14-year long-term experiment with a split-plot design was conducted, where the main plots received different cover crop treatments (bare vs. cover crop), and subplots were subjected to four fertilizer treatments (CK, M, NPK, MNPK). The significant main and interactive effects of cover crops, fertilizer treatment, and growth period on soil nutrients were observed (p < 0.001). Both cover crop and fertilizer treatments significantly increased the soil organic matter content, with implications for orchard resilience to drought. However, the cover factor alone did not notably influence soil carbon–nitrogen ratios or microbial communities. Microbial carbon limitations were driven by soil water dynamics and microbial biomass, while microbial phosphorus limitations were closely linked to total nitrogen levels. The results underscore the combination of cover crops and MNPK fertilizer-enhanced soil nutrient levels and enzyme activities, mitigating microbial carbon and phosphorus limitations. These findings suggest practical strategies for optimizing fertilization practices to improve soil fertility and address nutrient constraints in orchard ecosystems.

Winter cover crops decreased soil mineral N contents and increased soil organic C stocks and N2O emission

Cover crops (CC) can contribute to climate protection as a result of their effects on soil nitrogen (N) cycling and nitrous oxide (N2O) emission and by increasing soil organic carbon (SOC) stocks. This study explored the influence of different winter CC (saia oat, winter rye and spring vetch) compared with bare fallow, followed by silage maize on N2O emissions and soil mineral N (SMN) dynamics, as well as on SOC stocks in year-round replicated field plot experiments in four fields located at two sites in northern Germany (Kiel, Uelzen) over two consecutive years (2018/19 and 2019/20). Non-legume CC decreased SMN contents in 0–30 cm during the CC period, but this did not result in decreased cumulative N2O emissions over that time. Decreased emissions during CC growth were offset by increased emissions during CC mineralisation after frost and incorporation. Higher cumulative N2O emissions during the maize period in all CC treatments compared with bare fallow (significant for non-legume CC) indicated that the incorporated CC biomass still boosted N2O emissions under the following crop. Overall, including CC in the cropping system increased annual and yield-related N2O emissions compared with bare fallow (significant only for non-legumes). The increase in annual N2O emissions of 0.84 ± 1.06 kg N2O-N ha−1 yr−1 was only partly offset by the estimated mitigation potential for indirect N2O emissions of 0.52 ± 0.14 kg N2O-N ha−1 yr−1. The mean annual increase in SOC induced by growing CC every fourth year over a 50-year period was 40–60 kg C ha−1 yr−1. In summary, CC had both positive and negative effects on greenhouse gas exchange. Site and crop rotation optimised CC systems, and a more precise and site-specific consideration of fertilising effects might help improve the net greenhouse gas budget of CC.

A native plant species cover crop positively impacted vineyard water dynamics, soil health, and vine vigor

Cover cropping is associated with multiple ecosystem and agronomic benefits. However, in irrigated orchards and vineyards of the dry, Western United States, cover crop adoption rates are low, often owing to concerns over their uptake of critical soil water. Regional concerns, such as this, must be addressed to identify sustainable agricultural practices that meet unique needs of diverse growing regions. A two-year study was conducted to determine the impacts of cover crops on soil water dynamics, soil health, and crop growth during the establishment of an Autumn King table grape vineyard in a semi-arid, Mediterranean climate, specifically the Central Valley of California. Phacelia (Phacelia tanacetifolia), a plant species native to the region, and an introduced species, rye (Secale cereale L. ‘Merced’), were planted as cool season cover crops in the interrow spaces of the grapevines and compared to a standard management practice of no cover crop interrow spaces. The cover crop treatments differentially impacted soil microbial biomass and soil aggregate stability, with the phacelia treatment enhancing both metrics from the first season. The phacelia treatment plots resulted in higher soil moisture beneath the vines in both years, while the rye treatment showed similar benefits only after two consecutive years of cover cropping. Vine vigor was also higher in the phacelia treatment, which was likely consequential of enhanced soil moisture in the rows. Compared to the rye, the phacelia had lower plant tissue carbon to nitrogen ratio and higher above ground plant biomass, which may underpin the soil health benefits associated with the phacelia, although variances in soil total carbon and nitrogen and ammonium and nitrate were not determined for any treatment. Altogether, we present information on cover crop plant traits that show quicker return on investment with regards to soil health improvements and water savings. Further, we demonstrate that cool season cover crops offered benefits for vineyard water productivity. In summary, for Mediterranean vineyards, cover crops can promote vineyard soil quality and be a component of sustainable water management.

Cover crops and irrigation impacts on corn production and economic returns

Increases in irrigated crop acreage and frequent droughts during the growing season have caused continual groundwater decline of the Mississippi River Valley Alluvial Aquifer in the Mississippi Delta region. A field experiment was conducted from 2019 to 2021 to determine if combinations of irrigation scheduling thresholds and cover crops (CCs) could improve corn (Zea mays L.) production, water productivity (WP), irrigation water use efficiency (IWUE), and net returns. The irrigation thresholds used for irrigation scheduling were a wet threshold (−40 kPa), a dry threshold (−90 kPa), and no irrigation. The CC treatments were cereal rye (Secale cereale L.), hairy vetch (Vicia villosa R.), wheat (Triticum aestivum L.)-radish (Raphanus sativus L.)-turnip (Brassica rapa L.) mix, and no cover crop. In 2020, CCs reduced corn yield by 9–26% compared to no cover crop. In 2021, wet irrigation threshold treatments had 8% and 9% higher corn yield than no irrigation and dry irrigation threshold treatments, respectively. No irrigation treatments showed higher WP than dry and wet irrigation thresholds, while hairy vetch had higher in WP among CC treatments in year two of this study. Hairy vetch under the dry irrigation threshold had higher IWUE than all other treatments. The no-CC treatments generated $167, $340, and $58 ha−1 more under the wet, dry, and no irrigation treatments, respectively, when averaged over both years. Water conservation was affected by CC selection and irrigation management.

Interseeded cover crops in wide‐row corn: An opportunity for northern cropping systems

AbstractCover crops are an effective way to reduce soil erosion and promote soil health. However, in North Dakota and other northern climates where corn (Zea mays L.) is an important commodity crop, killing frosts generally occur before harvest, leaving little opportunity for cover crop planting. By interseeding cover crops into corn during the growing season, the cover crops are given a longer period to establish. The purpose of this study was to identify the impact cover crops interseeded into wide‐row (60‐inch) corn have on soil water content and corn productivity. Two experimental sites were established in 2020 near Leonard and Rutland, ND. Both sites were organized into randomized complete block designs, with three cover crop treatments in Leonard (n = 9) and four cover crop treatments in Rutland (n = 16). Cover crops were no‐till drilled into the corn at the V4 growth stage. The cover crop treatments were diverse mixes developed to either provide pollinator habitat, overwinter, or winter‐kill. Throughout the growing season, soil gravimetric water content and cover crop biomass was monitored. At the end of the growing season, dry cover crop biomass ranged from 189 to 1445 lb ac−1. The presence and type of interseeded cover crops did not have a statistically significant effect on soil water content or corn yield. It is suspected the above average precipitation during the month of July led to adequate amounts of soil water for the entirety of the cover crop growing season, limiting the difference between treatments.

Effect of ultra‐early, early, and normal soybean planting dates and rye cover crop on soybean grain yield

AbstractWith changes to climate and crop insurance, earlier soybean [Glycine max (L.) Merr.] planting dates need to be investigated. Additionally, the use of a cover crop prior to soybean is promoted as a sustainable practice though little is known about cover crop and ultra‐early soybean planting (prior to April 15). The objective was to evaluate soybean planting date and cereal rye (Secale cereale L.) cover crop termination timing on cover crop biomass, soybean plant population, and yield. The study was conducted in Northeast and West Central Ohio in 2021 and 2022. Treatments included three soybean planting dates (early April, late April, and late May) and three cover crop treatments (termination 1–2 weeks prior to planting or “early,” termination at or after planting or “late,” and no cover crop). Cover crop biomass increased as termination was delayed. Soybean planted in early April resulted in a yield reduction of 1.8 Mg ha−1 when planted into a cover crop compared to the no cover crop control. However, when soybean was planted in late April, grain yield was not different among cover crop treatments. Yield reduction associated with early April planting with a cover crop was likely due to low soybean plant population, especially in Northeast Ohio, where plant population was <55,000 plants ha−1 with a cover crop and >120,000 plants ha−1 without a cover crop. To maximize yield, soybean should be planted by the end of April in Northeast Ohio. In West Central Ohio, soybean can be planted in early April without a cover crop.

Winter cover cropping to improve soil health in semiarid, irrigated cropping systems of Central Oregon

AbstractA 1‐year experiment was conducted in Madras, OR, to examine the ability of winter cover crops (CCs) to improve physical, chemical, and biological soil properties over a bare fallow control. Competition for water is frequently seen as an obstacle to cover cropping in semiarid, irrigated systems. Benefits from CCs need to be demonstrated and quantified in regions such as Central Oregon's high desert for growers to make cost/benefit analysis decisions. To support such decisions, the effect of eight winter CC treatments (two brassicas, four legumes, two cereal mixtures) on five agronomic parameters and 39 soil health indicators (0–5 cm) were measured in the spring of 2019 after 8 months of CC growth. We identified four soil indicator response patterns in reference to the fallow: (i) steady improvement over fallow across all CCs (16 indicators, with hairy vetch and turnip being most efficient); (ii) marked improvement over fallow but somewhat constant response among CCs (organic C and N, surface hardness); (iii) negligible change from fallow; and (iv) varied response to CCs including both a deterioration and an improvement of soil health. Overall, 13 soil health indicators and five agronomic parameters responded significantly to CC treatment. CCs generated a stronger response of soil chemical and biological parameters than physical (average 82%, 79%, and 18% improvement over fallow, respectively). Hairy vetch had the greatest positive impact on soil biological and chemical properties but the lowest average impact on physical indicators. Winter CCs do offer soil health benefits in Central Oregon but should not be viewed as a short‐term fix to physical soil deficiencies. Our study provides strong evidence for the general ability of CCs to improve soil health in water‐limited systems. It also demonstrates the need for further studies focused on multiyear rotations, especially related to the improvement of soil physical properties such as soil moisture availability.

Presence of foodborne pathogens and survival of generic Escherichia coli in an organic integrated crop-livestock system

IntroductionIntegrated crop-livestock systems (ICLS) use animals to graze crop residues or cover crops before planting fresh produce and provide ecosystem services to support organic vegetable production. However, there is a risk of foodborne pathogen transfer to fresh produce because grazing may introduce enteric foodborne pathogens into the soil via animal feces, which may subsequently be transferred to the produce.MethodsTo examine the effect of cover crop use and the risk of cover crop grazing on the contamination of soil and produce by foodborne pathogens in ICLS, a three-year (2019–2021) experimental study was conducted in organically managed plots, which were assigned three different treatments (fallow without cover crop or grazing, cover crop without grazing, or cover crop with grazing by sheep) in a maize/tomato rotation. During the three years of the experiment, a total of 184 pre- and post-graze fecal samples and 96 samples of tomatoes were collected to test for foodborne pathogens (Escherichia coli O157, non-O157 Shiga toxin-producing Escherichia coli (STEC), and Listeria (L.) monocytogenes). Soil samples were collected monthly until 126–171 days after grazing (824 in total) to examine the presence of foodborne pathogens, and generic E. coli (MPN/g) was quantified to compare its persistence among the three treatments.Results and DiscussionWe did not detect any foodborne pathogens from harvested tomatoes in 2020 and 2021. One non-O157 STEC positive soil sample (0.1%, 1/824) was detected in the fallow treatment, and one L. monocytogenes-positive (1.1%, 1/92) was detected from the post-graze fecal samples. When assessing proportions of generic E. coli positive and counts of generic E. coli in the soil samples using mixed effect zero-inflated negative binomial models, soil samples collected in the graze cover crop treatment plot showed significant increases in the counts of generic E. coli until 61–82 days post grazing, but no difference was observed after 96–123 days, compared to the baseline of the fallow treatment. Findings from generic E. coli counts support the use of the United States Department of Agriculture (USDA) National Organic Program (NOP) 90- or 120-day interval rule between applying raw manure and harvesting in organic farming into ICLS. Additionally, we confirmed that commercial organic compost application before cover crop seeding in the winter had no significant effect on the proportions and counts of generic E. coli in the soil of the following growing seasons. This longitudinal field trial confirmed that the effect of sheep grazing on foodborne pathogen contamination in ICLS is minimal but further studies comparing the genetic associations between fecal and soil samples would be necessary to distinguish the source of foodborne pathogen contamination.

Cover crops improve soil structure and change organic carbon distribution in macroaggregate fractions

Abstract. Soil structure is sensitive to intensive soil management. It can be ameliorated by a reduction in soil cultivation and stimulation of plant and microbial mediators for aggregate formation, with the latter being a prerequisite and measure for soil quality. Cover crops (CCs) are part of an integrated approach to stabilize or improve soil quality. Thereby, the incorporation of diverse CC mixtures is hypothesized to increase the positive effects of CC applications. This study entailed an investigation of the legacy effect of CCs on soil aggregates after three crop rotations in the second main crop (winter wheat) after the last CC treatment. Four CCs (mustard, phacelia, clover, and oat) cultivated in pure stands and with a fallow treatment were compared to a mixture of the four CC species (Mix4) and a highly diverse 12-plant-species mixture (Mix12) in a long-term field experiment in Germany. The organic carbon (OC) distribution within macroaggregate fractions (16–8, 8–4, 4–2, 2–1, and <1 mm) and their aggregate stability were measured by dry- and wet-sieving methods, and the mean weight diameter (MWD) was calculated from water-stable aggregates. The results showed that, compared to the fallow, all CCs increased the MWD between 10 % and 19 % in soil under the following main crop. The average MWD increase over the fallow was slightly higher for CC mixtures (16 %) than for single CCs (12 %). Most of the OC (67.9 % on average) was stored in the <1 mm aggregate fraction, highest in the topsoil and decreasing with soil depth. The intermediate fractions (8–4 mm, 4–2 mm, 2–1 mm) stored 8.5 %, 10.5 %, and 11.0 % of the total OC, while 2.1 % was stored in the 16–8 mm fraction. Higher MWD improvement at the 20–30 cm depth also indicates additional benefits from a reduction in the cultivation depth. Structural equation modelling (SEM) suggests that single CCs were more likely to increase OC storage in small macroaggregates <1 mm, while CC mixtures were more likely to increase OC in the largest fraction (8–16 mm). Different individual CC species or mixtures exhibited varying involvement in the formation of different aggregate fractions. We provide evidence that litter quality, root morphology, and rhizosphere input, which affect microbial mediators of aggregate formation, might be the main reasons for the observed differences between CC treatments. Cover crops are valuable multifunctional tools for sustainable soil management. Here, we showed that they contribute to structure amelioration in arable soils. Increasing the functional diversity of plant species in CC mixtures could be a strategy to further enhance the positive effects of CCs in agroecosystems.

Cover Crop and Crop Rotation Effects on Tissue and Soil Population Dynamics of Macrophomina phaseolina and Yield Under No-Till System.

The effects of crop rotation and winter cover crops on soybean yield and colony-forming (CFU) units of Macrophomina phaseolina, the causal agent of charcoal rot (CR), are poorly understood. A field trial was conducted from 2011 to 2015 to evaluate (i) the impact of crop rotation consisting of soybean (Glycine max [L.] Merr.) following cotton (Gossypium hirsutum L.), soybean following corn (Zea mays L.), and soybean following soybean over a 2-year rotation and its interaction with cover crop and (ii) the impact of different cover crops on a continuous soybean crop over a 5-year period. This trial was conducted in a field with 10 subsequent years of cover crop and rotation treatments. Cover crops consisted of winter wheat (Triticum aestivum L.) and Austrian winter pea (Pisum sativum L. subsp. sativum var. arvense), hairy vetch (Vicia villosa Roth), and a fallow treatment was evaluated with and without poultry litter application (bio-cover). Tissue CFU of M. phaseolina varied significantly between crop rotation treatments: plots where soybean was grown following cotton had significantly greater tissue CFU than plots following soybean. Poultry litter and hairy vetch cover cropping caused increased tissue CFU, though this effect differed by year and crop rotation treatment. Soil CFU in 2015 was substantially lower compared with 2011. However, under some crop rotation sequences, plots in the fallow treatment had significantly greater soil CFU than plots where hairy vetch and wheat was grown as a cover crop. Yield was greater in 2015 compared with 2011. There was a significant interaction of the previous crop in the rotation with year, and greater yield was observed in plots planted following cotton in the rotation in 2015 but not in 2011. The result from the continuous soybean planted over 5 years showed that there were no significant overall effects of any of the cover crop treatments nor was there interaction between cover crop treatment and year on yield. The lack of significant interaction between crop rotation and cover crop and the absence of significant differences between cover crop treatments in continuous soybean planting suggest that cover crop recommendations for midsouthern soybean growers may need to be independent of crop rotation and be based on long-term crop needs.

Influence of soil management on vegetative growth, yield, and wine quality parameters in an organic “Pedro Ximénez” vineyard: field and UAV data

The use of cover crops in vineyards is expected to increase due to the strong encouragement by European agricultural policy and their contribution to reducing soil erosion. This paper presents the results obtained over three years in a vineyard of the “Pedro Ximénez” variety organically grown in southern Spain. The influence on production, vigor, and grape quality of a seeded cover crop versus tillage was compared using field data and imagery acquired by an uncrewed aerial vehicle. The vines under tillage showed greater vegetative development and yield than those with cover crops between rows. The grapes from the vines under the cover crop treatment ripened earlier and presented higher values of total soluble solids, characteristics that can be useful in the protected designation of origin where the study field is placed. However, the strong yield reduction caused by the cover crop treatment encourages future research to explore other cover crop species that could contribute to improving soil properties without compromising the profitability of the vineyard. This is the first time that the influence of cover cropping on the agronomic and oenological parameters of organically grown white vineyard varieties such as “Pedro Ximénez” has been assessed using field and UAV data.

Cover crop species influences soil fungal species richness and community structure.

Despite the well documented link between cover cropping and soil microbiology, the influence of specific cover crop species on soil microbes remains poorly understood. We evaluated how soil fungal communities in a no till system respond to four cover crop treatments: no cover crop (REF), cereal ryegrass (CRYE), wild pennycress (WPEN), and a mix of pea, clover, radish, and oat (PCRO). Soil samples were collected from experimental plots following termination of cover crops from depths of 0-2 cm and 2-4 cm where cover crops had significantly increased soil organic matter. There was no significant interaction between soil depth and cover crop treatment on either alpha diversity or beta diversity. All cover crop treatments (CRYE, PCRO, and WPEN) enhanced soil fungal richness but only CRYE enhanced soil fungal diversity and altered the fungal community structure. Soil depth altered the fungal community structure but had no effect on fungal diversity and richness. Genus Fusarium which includes some of the most economically destructive pathogens was more abundant in REF and PCRO treatments compared to CRYE and WPEN. In contrast, genus Mortierella which is known to promote plant health was more abundant in all cover crop treatments relative to the REF. These findings demonstrate that cover cropping can increase soil fungal species richness and alter fungal community structure, potentially promoting the abundance of beneficial fungi and reducing the abundance of some plant pathogens within the genus Fusarium. These effects are dependent on cover crop species, a factor that should be considered when selecting appropriate cover crops for a particular cropping system.

Improving semi-arid agroecosystem services with cover crop mixes.

Winter wheat (Triticum aestivum, L.) production in the semi-arid US Northern High Plains (NHP) is challenged by frequent droughts and water-limited, low fertility soils. Composted cattle manure (compost) and cover crops (CC) are known to provide agroecosystem services such as improved soil health, and in the CC case, increased plant diversity, and competition with weedy species. The main concern of planting CC in winter wheat fallow rotation in regions that are more productive than the NHP, however, is the soil moisture depletion. It is unknown however, whether addition of CC to compost-amended soils in the NHP will improve soil properties and agroecosystem health without compromising already low soil water content. The main objective of this study was to assess the effects of four CC treatments amended with compost (45 Mg ha-1) or inorganic fertilizer (IF) (.09 Mg ha-1 mono-ammonium phosphate, 11-52-0 and 1.2 Mg ha-1ammonium sulfate, 21-0-0) on the presence of weeds, soil and plant total carbon (C), nitrogen (N), and biological dinitrogen (N2) fixation (BNF). Mycorrhizal Mix (MM), Nitrogen Fixer Mix (NF), Soil Building Mix (SB), a monoculture of phacelia (Phacelia tanacetifolia Benth L.) (PH), and a no CC control (no CC) were grown in native soil kept at 7% soil moisture in a greenhouse for a period of nine weeks. When amended with compost, MM was the most beneficial (48 g m-2 BNF and 1.7% soil C increase). SB had the highest germination, aboveground biomass, and decreased weed biomass by 60%. It also demonstrated the second highest amount of BNF (40 g m-2) and soil C increase by 1.5%. On contrary, IF hindered BNF by almost 70% in all legume-containing CC treatments and reduced soil C by 15%.

Effects of Cover Crop and Filter Strips on Sediment and Nutrient Loads Measured at the Edge of a Commercial Cotton Field

Highlights Winter cover crops and growing season filter strips were implemented without sacrificing significant land and achieved positive results. Cover crops reduced runoff depth, peak flow rate, sediment, TP, and TN load by 30%, 49%, 43%, 4%, and 7%, respectively. Filter strips reduced runoff depth, peak flow rate, sediment, TP, and TN load by 36%, 49%, 56%, 15%, and 21%, respectively. Abstract. Effective use of conservation practices in agricultural fields can reduce sediment and other pollutant loads entering waterways. In this study, we evaluated the effectiveness of using cover crops and filter strips on sediment and nutrient loss at the edge of paired, 7.83 ha (19.35 ac), commercial cotton fields in the Lower Mississippi River Basin (LMRB) in northeastern Arkansas. Cover crops included winter wheat, black oat, and ryegrass seeded in the winter fallow period, while filter strips included a grassy turn row at the field border and switchgrass transplanted around the drainage pipe at the edge of the treatment field. The field border of the control field was generally free from vegetation. A monitoring system measured discharge and collected composite water samples from rainfall and irrigation runoff events. Water samples were analyzed for phosphate (PO4-P), total phosphorus (TP), nitrate (NO3-N), ammonium (NH4-N), total nitrogen (TN), and suspended sediment concentrations. Data were collected from 2015 to 2020. Baseline data were collected when both fields had similar conservation practices (i.e., no cover crops in 2015 and no filter strips in 2015 and 2016). A comparison of 66 common runoff events between the control and cover crop treatment fields during the non-growing season indicated that the median peak flow and sediment loads were significantly reduced (p < 0.05), with an average reduction of 49% and 43%, respectively. Similarly, a comparison of 55 common runoff events between the control and filter strips treatment fields during the growing season found that the filter strips reduced significantly with average runoff by 36%, peak flow by 49%, and sediment loads by 56% (p < 0.05). Nutrient load reductions by the cover crop and filter strip treatments were not significantly different than by the control (p > 0.05). However, mean PO4-P, TP, NO3-N, NO2-N, NH4-N, and TN loads in the cover crop treatment field were lower than in the control field by 21%, 4%, 9%, 4%, 17%, and 7%, respectively. Similarly, mean PO4-P, TP, NO3-N, NH4-N, and TN loads in the filter strip treatment field were lower than in the control field by 23%, 15%, 11%, 42%, and 21%, respectively. The results demonstrated runoff depth, peak flow rate, nutrients, and sediment load reductions following the implementation of cover crops and filter strips at the commercial field scale. Keywords: Agricultural conservation practices, BMPs, Cotton, Cover crop, Edge-of-field monitoring, Filter strips, Switch grass.