Cover Crop Species Research Articles

Cover crop species alter tallgrass prairie community assembly.

Cover crops are increasingly being used in ecological restoration projects, and are hypothesized to facilitate establishment of sown species by reducing weed abundances without competing with the target mix. We tested these predictions and examined the role of cover crop species on later species composition and diversity using cover crop seed treatments. Treatments included a fall seeding of one annual (Raphanus sativus or Avena sativa), one biennial (Oenothera biennis), one perennial species (Elymus canadensis), two grass-forb species combinations, or nothing as a control. All plots received the same diverse tallgrass prairie seed mix in March of the following year. Plant communities were sampled through five growing seasons. We found that cover crop treatments influenced community assembly, and that cover crop species varied in their effectiveness at reducing weed abundances, with the perennial grass E. canadensis being especially effective at reducing weeds. After 5 years, treatments were neutral in their effects on species diversity. However, composition of establishing plants (not including the cover crop) differed significantly among cover crop treatments on all sampling dates, indicating that treatments had long-term effects. Plots containing the C3 grass E. canadensis had greater abundance of C3 grasses and forbs, and reduced C4 grass abundance compared to other treatments. Our results indicate that cover crop species differ in their effects on assembling tallgrass prairie communities and that niche modification (i.e., species altering the abiotic environment in a way that favors species that benefit from the alterations) occurs when the cover crop is a perennial grass.

Effect of summer cover crops on cabbage yield, weed suppression, and N mineralization in a low input cropping system

Summer cover crops (SCCs) provide valuable agroecosystem services to growers using spring and autumn vegetable crop rotations. Choosing the right SCCs to maximize agroecosystem services and fit growers' interests is challenging due to the wide array of SCC functions and one benefit may come at the cost of another (i.e., a tradeoff). In particular, fast-growing grasses may produce greater SCC biomass but may immobilize plant-available N needed by the autumn vegetable crop. We conducted a field study in Ames, Iowa US to compare agroecosystem services – weed suppression, autumn cabbage yield, soil nutrients, and net nitrogen (N) mineralization of eight SCC species over 2 years. Cover crop species were grown for an average of 55 days and included: brown top millet (Panicum ramosum L., BTM), buckwheat (Fagopyrum esculentum Moench, “Mancan”, BW), cowpea (Vigna unguiculata (L). Walp., “Iron and Clay”, CP), flax (Linum usitassimum L. “Golden”, GF), mung bean (Vigna radiata (L.) R. Wilczek, MB), sunnhemp (Crotalaria juncea L., SH), sorghum sudangrass (Sorghum bicolor L. Moench x Sorghum sudanense Piper Staph. “Sorgrow BMR Dwarf”, SS), and Teff grass (Eragrostis tef (Zuccagni) “Selam”, TEF), and a no-SCC control (NCC) treatment. The range of mean cover crop biomass was 0.8 (cowpea) to 7.5 (teff grass) Mg ha−1. There was a strong, negative correlation between SCC biomass and weed biomass (R2 = 0.83). Low biomass producing legumes resulted in greater weed biomass, but 34–58% greater cabbage yield in one of two experimental years. Ion exchange membranes (IEMs) were not able to capture differences in total net N mineralization among SCC treatments however, soil inorganic N was greater under legume SCCs at SCC termination. We show there are tradeoffs when choosing SCCs between weed suppression and net N mineralization and that the environmental conditions, i.e., climate, regulate whether these tradeoffs favor greater vegetable crop yields.

Cover Crops as Reservoirs for Young Vine Decline Pathogens

Young vine decline (YVD) is a grapevine trunk disease (GTD) which results in stunted and delayed growth, reduced yield, root necrosis and eventually death of young vines. Given losses associated with root trunk disease, and increasing limits on chemical fungicides, there is a need for sustainable approaches to combat disease; (1) Cover cropping is a commonly used practice in agricultural systems and has potential to reduce disease in vineyards but there is a risk that cover crop species may act as a host for grapevine pathogens, increasing the risk of infection; (2) We tested 25 plant species commonly used in cover crops to assess their potential to act as a host for a Ilyonectria liriodendri, which is a causal agent of young vine decline. We inoculated greenhouse pots with a pathogeninc strain of Ilyonectria and assayed the roots for the presence of the pathogen; (3) Of the 25 cover crops tested, many of the species showed increased root abundance of Ilyonectria, compared to background levels. In particular phacelia (Phacelia tanacetifolia) and buckwheat (Fagopyrum esculentum) showed very high levels of root colonization. (4) This is the first study to our knowledge that highlights the potential of cover crops to soil borne fungal pathogens.

Effects of Carbon Amendments, Tillage and Cover Cropping on Arbuscular Mycorrhizal Fungi Association and Root Architecture in Corn and Cotton Crop Sequence

A field experiment was conducted to study the effects of carbon amendments, tillage, and cover cropping on arbuscular mycorrhizal fungi (AMF) association and root architecture at Farm Services at Texas A&M University. Three levels of carbon amendments at the rate of 500 kg C ha−1 (biochar, composted biosolid, and control (no carbon amendment)), two levels of tillage (conventional disking (CT) and no tillage (NT)), and two levels of cover crop (a mixture of oat, mustard, and pea (CC) and no cover crop (NCC)) were arranged in a split-split plot design with four replications. Over a two-year crop sequence of corn followed by cotton, AMF colonization of roots was 4.43% greater in biochar-treated soil than in the control treatment. Colonization in cotton was 5.17% and 6.09% greater under NT and CC treatments, respectively, compared to CT and NCC. Carbon amendments did not alter corn root length but did alter root angle at 20–30 cm. Carbon amendments did not affect root angle under CC. However, tillage did affect CC root length and angle. Root length and root angle were found to differ among the cover crop species. The results imply that farmers may combine certain practices to optimize and harness the benefits of AMF.

Frost killed cover crops induced high emissions of nitrous oxide.

Establishing a cover crop after harvest of a main crop in late summer or early autumn can have several advantages, including weed control, decreased nitrate leaching and an increased potential for carbon sequestration. However, the addition of fresh plant material to the soil in late autumn or winter, either by active termination of the cover crop or by frost damage, could be a risk factor for nitrous oxide emissions, due to the simultaneous occurrence of wet soil conditions and freeze-thaw cycles. We measured field emissions of nitrous oxide from three cover crops - oilseed radish, (Raphanus sativus var. oleiformis), phacelia (Phacelia tanacetifolia) and oats (Avena sativa) - over a 43-day period in winter. All three cover crops were sensitive to frost and died, wilted and started to decompose during this period. The cover crops increased nitrous oxide emissions, relative to controls that were ploughed in autumn, by 1.8, 0.7 and 0.6 kg N2O-N ha-1, for oilseed radish, phacelia and oats, respectively. We conclude that the choice of cover crop species and management options for cover crops need to be further researched to minimise their contribution to nitrous oxide emissions from agriculture.

Cover crop influence on pore size distribution and biopore dynamics: Enumerating root and soil faunal effects.

Pore structure is a key determinant of soil functioning, and both root growth and activity of soil fauna are modified by and interact with pore structure in multiple ways. Cover cropping is a rapidly growing popular strategy for improving agricultural sustainability, including improvements in pore structure. However, since cover crop species encompass a variety of contrasting root architectures, they can have disparate effects on formation of soil pores and their characteristics, thus on the pore structure formation. Moreover, utilization of the existing pore systems and its modification by new root growth, in conjunction with soil fauna activity, can also vary by cover crop species, affecting the dynamics of biopores (creation and demolition). The objectives of this study were (i) to quantify the influence of 5 cover crop species on formation and size distribution of soil macropores (>36 μm Ø); (ii) to explore the changes in the originally developed pore architecture after an additional season of cover crop growth; and (iii) to assess the relative contributions of plant roots and soil fauna to fate and modifications of biopores. Intact soil cores were taken from 5 to 10 cm depth after one season of cover crop growth, followed by X-ray computed micro-tomography (CT) characterization, and then, the cores were reburied for a second root growing period of cover crops to explore subsequent changes in pore characteristics with the second CT scanning.Our data suggest that interactions of soil fauna and roots with pore structure changed over time. While in the first season, large biopores were created at the expense of small pores, in the second year these biopores were reused or destroyed by the creation of new ones through earthworm activities and large root growth. In addition, the creation of large biopores (>0.5 mm) increased total macroporosity. During the second root growing period, these large sized macropores, however, are reduced in size again through the action of soil fauna smaller than earthworms, suggesting a highly dynamic equilibrium. Different effects of cover crops on pore structure mainly arise from their differences in root volume, mean diameter as well as their reuse of existing macropores.

PERFORMANCE OF VEGETABLE CROPPING AND EFFECTS ON SOIL PROPERTIES UNDER CONSERVATION AGRICULTURE MANAGEMENT IN SOUTHEASTEARN BRAZIL

Conservation Agriculture (CA) is based in principles of the minimum soil disturbance, preservation of organic mulch on soil surface and crop rotation. Therefore, this study aimed to compare the CA versus conventional tillage for tomato and broccoli cropping. The experimental treatments were two tillage method (no-tillage and conventional tillage) as the main plot and species of cover crops, legumes, grasses and a mix (legume + grass) as subplot. Soil properties and vegetable agronomic performance were assessment. No-tillage provided higher soil water content and increased soil fertility and higher soil mechanical resistance to penetration than conventional tillage. Broccoli growth and yield were impaired under no-tillage, while tomato had greater root length and similar yield compared to the conventional tillage. Regarding to the cover crops there was no difference on the experimental traits. Conservation Agriculture is recommended to increase soil fertility and soil water storage as well as for ensure sustainable vegetable production.

Differences in cover crop contributions to phosphorus uptake by ryegrass in two soils with low and moderate P status

Growing evidence has emerged that cover crops may be able to improve phosphorus (P) cycling and contribute to the P nutrition of the subsequent crop. This could be particularly important in farming systems, with limited access to inputs and where low soil P availability has been identified. In a pot experiment using soils labelled with radioactive 33P, we examined how a range of cover crop residues directly contribute to P uptake of ryegrass, as well as how they affect P uptake of ryegrass from the soil P pool. Two soils with a low and a moderate P status (6.3 and 15.3 mg Olsen-P kg−1 soil) were chosen for the pot experiment as models for soils that are gradually becoming depleted in available P.Residues from five cover crop species (buckwheat (Fagopyrum esculentum Moench), oilseed radish (Raphanus sativus L.), garden sorrel (Rumex acetosa L.), white lupine (Lupinus albus L.) and hairy vetch (Vicia villosa Roth)) showed a wide species-dependent variability in P concentration (3.4–8.8 mg P g-1 DM) and other quality traits. Cover crop residues contributed less to ryegrass growth and P uptake than the water-soluble P fertilizer. At the same P application dose, cover crops contributed 0.4–2.3 mg P kg−1 soil (18–42 %) to the total P uptake of ryegrass depending on species and soil P status, whereas mineral P fertilizer contributed up to 5.2 mg P kg−1 soil (46 %). In the low P soil, application of sorrel and radish significantly increased the P uptake of ryegrass compared to the control without P (by 93 and 75 %, respectively), whereas in the moderate P soil, sorrel and vetch increased the uptake (by 61 and 43 %, respectively). The cover crop effects on P uptake of ryegrass correlated significantly but only moderately well with their P concentration, content of water-extractable P and C:P ratio (R2 = 0.4, R2 = 0.4 and R2 = 0.5, respectively). As expected, the contribution of mineral fertilizer to P uptake of ryegrass was lower in the low P soil with a higher P sorption capacity compared to the moderate P soil, whereas the contribution of cover crops residues in these two soils was species-dependent. Addition of mineral fertilizer resulted in a greater uptake of soil P compared to the control whereas buckwheat and lupin with highest C:P ratios gave rise to a substantially smaller uptake of soil P, which is an indication of microbial P immobilization. Our study demonstrated that cover crop residues may contribute to the P nutrition of the subsequent crop, in some cases substantially, depending on the quality of the residues and the soil P status.

Leveraging functional traits of cover crops to coordinate crop productivity and soil health

Abstract Plants act as ecosystem engineers playing fundamental roles in steering their surroundings, including soil abiotic and biotic conditions, soil organisms, and the complex soil food web they comprise. Trait‐based approaches have been considered a ‘Holy Grail’ in linking plants to ecosystem functions, but the mechanistic relationship between plant traits and the soil food web as an indicator of soil health remains poorly understood. We examined this relationship for 16 cover crop species differing in leaf and root traits in a field experiment where corn, Zea mays was the main crop. Based on functional traits, the cover crop species were categorized into two ecological strategies at either end of the resource acquisitive‐conservative spectrum. We investigated the effects of cover crop ecological strategies on corn productivity and soil health. We used soil nematodes as an indicator of soil health and analysed soil physico‐chemical properties and microbial community activities. We found that acquisitive cover crops supported higher soil resource availability, bacterial energy channels in the soil food web, and greater corn productivity than conservative cover crops. In contrast, conservative cover crops supported higher abundances of fungivores and omni‐carnivores than acquisitive cover crop, which reflected a more structured and complex soil food web, implying a healthier soil ecosystem. Conservative cover crops also increased corn productivity compared to the no cover crop control treatment. Synthesis and applications. Collectively, this work shows that cover crops with distinct ecological strategies had their own strengths to enhance ecosystem functions: acquisitive and conservative cover crops improved crop productivity and soil health, respectively. These results indicates that farmers and policy makers can make trait‐based choices in selecting cover crop best serving the local needs. This points to a win‐win solution for food production and ecosystem sustainability.

Effects of the soil compaction on root growth of cover crops in the western Amazon

The intensification of agriculture has increased the traffic of heavy machines, which can cause soil compaction, becoming a limiting factor for plant growth and development. The aim of this work was to evaluate the effects of machine traffic on soil physical attributes, root growth and dry mass production of legumes and grasses cultivated as cover. The experiment was carried in Rolim de Moura (RO). The experimental design was randomized blocks, in a split-plot scheme, with three replications. The treatments in the plots consisted of four induced soil compaction states: 0, 1, 4, 7 passes of an agricultural tractor, and in the subplots four cover crops species: Crotalaria, Stylosanthes, Millet and Palisadegrass. After two days of intense rainfall, compaction was carried out by passing the wheelsets of a New Holland-TL85E agricultural tractor, with 88hp of power, 4x2 TDA, standard tires 7.5x16 and 18.4x34, with blowing pressure of 110 kPa and 124 kPa, with a total mass of 3.16 Mg. Density, microporosity, macroporosity and total porosity were evaluated, surface area, root length and diameter and dry mass were also evaluated. During the period of full flowering of each crop, trenches were opened in each subplot for root evaluation and deformed soil and shoot dry mass samples were collected for evaluation. Significant discrepancies were observed for the physical attributes evaluated, surface area, length and root diameter of grasses in relation to legumes. After a tractor pass, there is an increase in soil density, and reductions in macroporosity and total porosity.

Toward more sustainable tropical agriculture with cover crops: Soil microbiome responses to nitrogen management

Cover crops are a potential pathway for ecological cultivation in agricultural systems. In tropical no-till agricultural systems, the maintenance of residues on the soil surface and the addition of nitrogen (N) benefit the growth and grain yield of cash crops as well as the chemical and physical properties of the soil. However, the effects of these management practices on the soil microbiota are largely unknown. Here, we evaluated the effects of the timing of N application as a pulse disturbance and the growth of different cover crop species before maize in rotation on soil properties, maize productivity, and soil bacterial and fungal community diversity and composition. N fertilizer was applied either on live cover crops (palisade grass or ruzigrass), on cover crop straw just before maize seeding or in the maize V4 growth stage. Soils previously cultivated with palisade grass established similar microbial communities regardless of N application timing, with increases in total bacteria, total archaea, nutrients, and the C:N ratio. The soil microbial alpha diversity in treatments with palisade grass did not vary with N application timing, whereas the bacterial and fungal diversities in the treatments with ruzigrass decreased when N was applied to live ruzigrass or maize in the V4 growth stage. We conclude that palisade grass is a more suitable cover crop than ruzigrass, as palisade grass enhanced soil microbial diversity and maize productivity regardless of N application timing. Ruzigrass could be used as an alternative to palisade grass when N is applied during the straw phase. However, considering the entire agricultural system (soil–plant–microbe), ruzigrass is not as efficient as palisade grass in tropical no-till cover crop–maize rotation systems. Palisade grass is a suitable cover crop alternative for enhancing maize productivity, soil chemical properties and nutrient cycling, regardless of the timing of N application. Additionally, this study demonstrates that a holistic approach is valuable for evaluating soil diversity and crop productivity in agricultural systems.

Cover crop management practices to promote soil health and climate adaptation: Grappling with varied success from farmer and researcher observations.

Soil health is a pathway through which farm and environmental outcomes can be improved together on agricultural landscapes, and management to improve soil health is increasingly recognized as a strategy for agricultural producers to adapt to climate change-related impacts such as erosion and flooding. Many incentive programs exist or are in development to support the adoption of practices that promote soil health for these reasons, but few on-farm trials have compared the intersections of farmer versus researcher observations of soil health or of soil health compared with climate adaptation. The purpose of our study was to assess soil health outcomes and adaptation to simulated climate change in response to cover cropping on working farms enrolled in a Minnesota Natural Resources Conservation Service (NRCS)-funded Environmental Quality Incentives Program. This incentive program required the inclusion of diverse cover crop mixtures into existing farm crop rotations. We conducted farmer surveys, NRCS protocol field soil assessments, and NRCS-recommended laboratory assays on farms from across the state of Minnesota in a paired design comparing fields on the same or adjacent farms of the same soil mapping unit. Although 85% of farmers reported improvements in soil attributes or productivity, most field and laboratory assessments produced a high amount of variability in responsiveness to cover cropping. Despite this variability, we saw a significant decrease in bare ground and significant increases in earthworm counts, cellobiohydrolase microbial activity, and the Visual Evaluation of Soil Structure (VESS). Although researcher measurements did not show improvement in physical characteristics or infiltration other than the VESS field assessment, 67% of farmers reported improvements to the physical structure of the soil, associated with improved outcomes such as earlier planting dates and consistent crop growth across fields. When more than five species of cover crops were present, the percentage of reported improvements increased to >80%. We also found no significant improvement to climate change adaptation measured by nutrient or sediment loss after a simulated storm event. Together, our results suggest that adding a diverse annual cover crop mix to increase continuous cover can improve characteristics associated with soil health and that there needs to be a stronger focus in understanding variation in realized soil health outcomes on farms, including more co-creation of research with farmer partners.

The Weed-Suppressive Ability of Summer Cover Crops in the Northern Grains Region of Australia

Pressure is mounting on the agricultural sector to reduce reliance on herbicides for weed control leading to increased interest in the potential of cover crops to control weeds in summer fallows. The weed suppression ability of three summer cover crop species, buckwheat, millet and teff, was evaluated in field trials at two sites near Camden, NSW in 2021. Buckwheat, millet and teff reduced weed biomass by 65%, 77% and 95%, respectively at Bringelly and by 94%, 92% and 90%, respectively at Lansdowne. Following cover crop desiccation, teff residues reduced weed emergence in subsequently planted wheat by 73% and 26% at Bringelly and Lansdowne, respectively. Overall cover crops were found to be effective in suppressing weed emergence, growth, and reproductive capacity. These studies identified teff grass as an important summer crop option for the northern grains region.

Cotton yield and boron dynamics affected by cover crops and boron fertilization in a tropical sandy soil

Cover crops may affect diversely boron (B) availability and cotton yield, especially in tropical sandy soils. In turn, B fertilizer rates required by cotton can be dependent on the use of cover crops. This study aimed to evaluate cotton yield, soil-plant B dynamics, and soil fertility as a function of cover crops (fallow, millet, black velvet bean, and millet+ black velvet bean) and B fertilization rates (0, 1, 2, 4, and 6 kg ha −1 ). The experiment was carried out at the field in two crop seasons (2019/2020 and 2020/2021), in Dracena, São Paulo State, Brazil. Cover crops increased cotton fiber yields by 47% compared to fallow soil (average two crops), as well as improved B cycling and soil fertility. Proper B rates increased cotton fiber yield by 18%. A maximum cotton fiber yield was reached at 4 kg B ha −1 (millet + black velvet bean), 2 kg B ha −1 (black velvet bean) in the 2020/2021 crop season, and 1 kg B ha −1 in the other system. Critical levels of leaf B ranged from 12 to 16 mg kg −1 . Maximum B uptakes were 182 and 232 g B ha −1 in the first and second crop seasons, respectively. Boron application and cover crops increased B contents in the soil, but it was below 0.6 mg B dm −3 in the topsoil. When associated with B fertilization, cover crops, especially the intercropping between millet and black velvet bean, improved soil fertility, plant nutrition, and cotton fiber yields in the tropical sandy soil. • Cover crops and boron fertilization increases cotton yield in sandy soils. • Millet and black velvet bean are suitable options as cover crops on sandy soils. • Cover crops improve soil fertility and boron cycling. • Boron fertilization rates may vary with cover crop species and soil organic matter contents. • High rates of boron increase its soil stock, but also increase its leaching.

Cover crops maintain or improve agronomic performances of maize monoculture during the transition period from conventional to no-tillage

Maize monoculture systems often cause environmental impacts such as soil erosion, nitrate leaching and pesticide transfer. Conservation tillage and the use of cover crops appear to hold promise for limiting these impacts, but questions about their performance remain, particularly during the transition period after conventional soil tillage ceases. In this study, effects of no-tillage maize and fallow-period management with different cover crop species, either pure or in mixtures, were studied on the agronomic performance of maize and on soil N and water dynamics. The study combined field experiments over three years (2012–2014) and simulation modelling with the STICS model. The biomass of cover crops produced during the fallow period varied from 0.8 to 10.5 t dry matter ha−1 depending on the cover crop species and date of termination. Differences in soil water content were quantified among the treatments studied, with the lowest water content at the beginning of the maize growing season with late termination of a cover crop composed of pure faba bean or a vetch-oat mixture in 2014 (25–50% of plant-water available capacity). Maize grain yields ranged from 8.5 to 13.6 t dry matter ha−1, with the lowest yields in the bare soil treatment. Simulations with STICS were consistent with the observations and indicated a decrease in drainage of 8–38 mm year−1, depending on the year and cover crop. Introducing cover crops into maize systems is a powerful mechanism for maintaining production while improving environmental performances during the transition phase of soil properties in conservation tillage.

Mixed planting reduces the shaping ability of legume cover crop on soil microbial community structure

Cover crop species and management are the key factors for reaping maximum benefits. Current studies lack a comprehensive assessment of the effects of cover crop species and planting patterns on soil properties, plant properties, and rhizosphere microbial communities at the full-blooming stage. A field experiment was conducted for 8 years (2011–2018) in Tianjin (fluvo-aquic soil) in China to compare various cover crops (hairy vetch, February orchid and rye) under different planting patterns (monoculture or mixed culture) in terms of cover crop biomass, soil physicochemical and biological properties, and rhizosphere microbial communities through high-throughput sequencing. The following groups were established: CK (winter fallow; the control), FO (February orchid monoculture), RY (rye monoculture), HV (hairy vetch monoculture), FOHV (February orchid–hairy vetch mixed culture), and RYHV (rye–hairy vetch mixed culture). RY had the highest biomass and nitrogen (N) uptake, and HV had the lowest biomass and highest N content. Mixed culture produced biomass higher in amount than the average biomass of monocultures of each individual species. RYHV showed a higher amount of biomass and uptake of nutrients, especially N. Cover crop planting significantly increased soil organic matter content (22.45 %–33.22 %), N levels (78.28 %–412.04 %), and available phosphate (9.70 %–45.03 %) and potassium (20.71 %–56.62 %) levels, but no significant differences in soil pH and total phosphorus content were found among the treatments. FO and HV treatments showed higher increments in soil biological properties: soil microbial biomass C (Cmic) and soil microbial biomass N (Nmic) and nematode density than the RY treatment. Mixed planting further promoted these properties, and FOHV treatment showed the highest values, which indicated improved soil properties. HV treatment significantly reduced bacterial and fungal diversity and the number of operational taxonomic units. These effects can be alleviated by mixed planting with FO and RY. Principal component analysis showed that the bacterial and fungal communities in the control were distinct from those in the cover crop treatments, and the difference was the greatest in the HV treatment. However, mixed planting with FO and RY reduced this difference between HV and CK. Structural equation model integration and analysis confirmed that the bacterial community was primarily regulated by soil physicochemical properties, whereas the fungal community was primarily regulated by plant properties. Soil biological properties affected bacterial and fungal communities, and mixed planting alleviated the impact of hairy vetch on soil microbial communities.

Cover Crop Species Affect N2O Emissions at Hotspot Moments of Summer Crops

The use of cover crops, combined with low N fertilization and no-tillage, reduces the environmental impacts of agriculture. Legume cover crops provide N to the agroecosystem and allow N fertilization to be reduced without losing productivity, but may also increase nitrous oxide (N2O) emissions. Our main objective was to evaluate the impact of using oats, vetch, and oats+vetch mixture as cover crops on N2O emissions and summer crop yields in a maize–soybean rotation with low N fertilization to maize (32 kg N ha−1) under no-tillage. We also studied how the different cover crops affected soil variables related to N2O emissions. For the treatments that included vetch (vetch and oats+vetch), plots without N fertilization were included to evaluate if N2O emissions and crop yield were increased by low-rate N fertilization after a legume cover crop. We measured N2O emissions using static chambers in a long-term experiment located in the Argentine Pampas. We selected measurement periods in which high N2O fluxes were expected to evaluate the effect of the different cover crops during these hotspots. In the early stages of maize and soybean, the use of vetch as a cover crop increased N2O emissions compared with oats and a control without a cover crop. In those early stages, conditions for high N2O flux occurrence were promoted by the use of cover crops, as they increased soil moisture and, when vetch was the cover crop, nitrate content. Although the oats+vetch mixture reduced soil nitrate availability compared with vetch, this was not reflected lower N2O emissions. The use of oats as a cover crop did reduce N2O emissions compared with vetch and also decreased maize yields by 30.6%. The low-rate N fertilization in treatments that included vetch as a cover crop did not increase N2O emissions or yield significantly. Our study demonstrates that in low-input cropping systems under no-tillage, the use of legume cover crops can favor yields and also increase N2O emissions during the early stages of the following cash crop. Consequently, future work should explore mitigation strategies during this period.

Cover crops enhance resource availability for soil microorganisms in a pecan orchard

Currently, there are substantial knowledge gaps on the impacts of cover crops on soil resources in tree cropping systems, wherein they are typically planted in interrow alleys and maintained for multiple years. While cover crops uptake soil nutrients and water, they can also prevent soil water evaporative losses and return nutrients to soils via decomposition of plant residues and stimulation of microbial nutrient cycling. This field sampling study examined variances in soil conditions across 5- and 7-year-old, cover cropped pecan orchards. We collected soil beneath cover crops and beneath adjacent trees, where soil was kept bare, to evaluate impacts of cover on the soil biota, nutrients, carbon, and their dynamics across a production season. We employed routine soil chemical analyses, phospholipid fatty acid (PLFA) analysis, and high throughput sequencing of 16 S rRNA genes and ITS regions for soils collected at four time points. We revealed that the cover cropped alley soils contained higher relative abundances of microbes that use labile soil substrates in resource rich conditions than did the tree row soils. Soil chemical analyses provided additional evidence that the cover crops did not deplete soil nutrients and reduce soil moisture, but rather, enhanced soil nutrient and moisture contents during many of the sampling time points. Notably, cover crop plant species correlated with soil nutrients and plant beneficial microbes, which may warrant consideration when selecting cover crop species. The tree row and cover cropped alley soils had different proportions of plant-beneficial mycorrhizal fungi. The tree rows supported higher numbers of ectomycorrhizal (ECM) fungi and alleys had higher relative abundances of arbuscular mycorrhizal (AM) fungi, suggesting potential benefits for tree species like pecan, which support dual colonization by AM and ECM Fungi. Altogether, the cover crops enhanced soil carbon, nutrients, and microbial populations in a pecan orchard and these impacts were frequently larger in a 7-year-old versus 5-year-old orchard.

Is Harvesting Cover Crops for Hay Profitable When Planting Corn and Soybean in Tennessee?

Winter cover crops can improve the soil’s moisture-holding capacity, reduce soil water evaporation, and mitigate water-induced soil erosion; however, economic studies show mixed results on cover crop impacts on profits. One way to potentially increase the profits from planting cover crops is to harvest the cover crop for hay. The objective of this study was to determine the profitability of planting and harvesting cover crops when planting corn (Zea mays) or soybean (Glycine max (L.) Merr.) as a cash crop. We determined the difference in net returns among 15 cover crop species when planted before corn and soybeans. We then calculated the breakeven hay price if the cover crop was harvested. Data were collected from an experiment in Tennessee, from 2017 to 2019, at two locations. There was no difference in net returns across cover crop treatments for both corn and soybeans, thus indicating that planting a cover crop does not reduce profits. The breakeven prices for harvesting cover crops suggest that this system would not likely be profitable for corn but might be profitable if planting soybeans, depending on labor availability and local demand for hay.

Cover Image, Volume 51, Issue 3

On the cover: Plots on sandy soils in the coastal plain of Maryland where nitrogen leaching was measured under different cover crop species (left to right: no‐cover control, pure cereal rye, pure forage radish, and a radish‐rye‐crimson clover mixture). See N. Sedghi and R. Weil, “Fall cover crop nitrogen uptake drives reductions in winter‐spring leaching,” https://doi.org/10.1002/jeq2.20342. Photo by Ray Weil. image