Cover Crop Plots Research Articles

Does a native and introduced cover crop species differ in their ability to suppress weeds? A study in a table grape vineyard

This study compared the weed suppression ability of a native cover crop species phacelia (Phacelia tanacetifolia), an introduced cover crop species rye (Secale cereale L.), and a no cover crop (herbicide‑managed) system in a vineyard. Cover crops were sown in the interrow spaces of the grapevine rows. Percent weed cover after the cover crop termination was lower in the interrow of the phacelia than the no cover crop plots. During the cover crop growing season, phacelia suppressed weeds more than rye. However, the weed seedbank of the cover crop plots was greater than that of the no cover crop plots.

Long‐term tillage and cover cropping differentially influenced soil nitrous oxide emissions from cotton cropping system

AbstractClimate‐smart agricultural practices, such as no‐tillage (NT) and cover cropping, have been widely adopted and are anticipated to yield multiple benefits, including soil carbon sequestration, enhancing soil health, and crop yield stability. However, their influence on nitrous oxide (N2O) emissions varies, with the potential of both increasing and decreasing N2O emissions. Increasing N2O emissions under these practices may potentially offset the climate mitigation benefits from increased soil carbon sequestration. We investigated N2O emissions in response to 42 years of long‐term adoption of NT and legume cover crop, under nitrogen (N) rates of 0 and 67 kg N ha−1, in a continuous cotton system in the Southeastern United States. Intensive manual chamber‐based measurements were conducted over two growing seasons (2021–2022 and 2022–2023). Long‐term NT did not significantly affect cumulative N2O emissions during the study period (p > 0.05). Hairy vetch cover crop‐grown plots emitted two to three times more N2O than those without cover crops in 2021–2022, with no significant effect observed in 2022–2023. Cumulative emissions in cover crop plots were greater compared to those in no cover crop plots when fertilized with 67 kg N ha−1 in 2021–2022; however, this trend did not persist in 2022–2023. While interannual variability exists, our results generally suggest that long‐term NT may not increase N2O emissions, hence its adoption could enhance its broader soil health and climate benefits via soil carbon sequestration, whereas managing legume cover crop residues in N‐fertilized systems is critical to mitigate N2O emissions.

Summer cover crop and temporary legume-cereal intercrop effects on soil microbial indicators, soil water and cash crop yields in a semi-arid environment

ContextFew studies have investigated summer cover crops as a replacement for bare fallow in semi-arid temperate regions, and summer cover crop impacts on soil biological function, water balances and subsequent winter crop yields in these regions remain largely unknown. ObjectiveThe 4-year field study aimed to determine the consequences of replacing a summer fallow with a summer growing cover crop on soil function, water balances and subsequent winter cash crop yields in a semi-arid region (486 mm mean annual rainfall) of the Australian southern cropping zone. MethodsA canola (Brassica napus)-wheat (Triticum aestivum L.) rotation with summer fallow was compared to the same rotation with either i) a single species (buckwheat, Fagopyrum esculentum L.) summer cover crop; ii) a four-species mixed brassica + cereal summer cover crop or iii) a cropping sequence with a temporary legume intercrop in the wheat phase of the rotation. Cover crop biomass production, soil water to a depth of 90 cm at cash crop sowing, crop yields and soil functional indices were quantified. ResultsCover crops produced 500–700 kg biomass ha−1 in the 2020 and 2021 seasons and 1000–2400 kg biomass ha−1 in 2022. The four-species mixed cover crop significantly lowered soil water (around 30 mm; P < 0.05) at the time of sowing the cash crop compared to the control and resulted in 15% reduction (P = 0.12) in canola seed yield in 2020, but no significant effect of cover crops of soil water and mineral N at sowing, or cash crop yields, were observed in subsequent seasons. In 2021 the temporary vetch intercrop produced > 1000 kg ha−1 biomass over 9 weeks, and led to a (non-significant) 10% wheat yield reduction. There was no significant effect of cover crop or temporary intercrop treatments on soil functions in the 2020 or 2021 seasons, but activities of several soil enzymes (leucine aminopeptidase, arylsulfatase and B-glucosidase; P < 0.05) and water-soluble carbon (P = 0.059) were significantly higher in the summer cover crop plots compared to control and intercrop plots in March 2022 following termination of the cover crops. These changes coincided with a significant increase in saturated hydraulic conductivity in the four-species cover crop plots in March 2022 compared to control plots. ImplicationsThe study did not provide any compelling evidence for benefits of summer cover crops over fallow in the short term (3–4 years). The relatively low cover crop biomass production over the 4-year study suggests summer cover crops are unlikely to substantially improve soil carbon levels in temperate, semi-arid cropping systems.

Soil carbon and aggregate stability are positively related and increased under combined soil amendment, tillage, and cover cropping practices

AbstractAgricultural practices alter the organic carbon dynamics in soil. An experiment was conducted to study the effect of carbon amendments, tillage, and cover cropping on permanganate oxidizable carbon (POXC), total organic carbon (TOC), and wet aggregate stability (WAS) in a 2‐year crop sequence (corn–cover crop–cotton–cover crop) at the Texas A&amp;M Research Farm. Two carbon amendments (biochar and composted biosolid) were applied at the rate of 500 kg C ha−1, along with a control. Two tillage practices were evaluated: conventional tillage (CT) and no‐tillage (No‐Till). A cover crop (CC) mixture of oat, mustard, and pea and no cover crop (No‐CC) were also evaluated. Treatments were arranged in a split‐split plot design with four replications. Amending the soil with carbon as composted biosolid or biochar affected POXC at both the 0‐ to 5‐ and 5‐ to 15‐cm depths. The POXC was significantly higher for the biochar treated plots for corn and CC after corn but significantly lower POXC was observed after cotton with biochar‐treated plots. The POXC increased under No‐Till compared with CT and CC plots relative to No‐CC plots. The TOC was not sensitive to soil management practices. The POXC and TOC both decreased with depth. The WAS greater under No‐Till and CC plots. The POXC and WAS were influenced by soil management practices and can be useful indicators to assess short‐term soil health improvements. The POXC and WAS were positively related, suggesting that one may be used to predict the other.

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

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

Evaluation of winter cover crop methods for management of flatheaded appletree borer (Coleoptera: Buprestidae).

Winter cover crops grown at the base of red maples (Acer rubrum L.) can reduce flatheaded appletree borer (Chrysobothris femorata Olivier; Coleoptera: Buprestidae; FAB) damage by both physically blocking preferred oviposition sites and altering the environment around them. However, cover crop competition negatively affects tree growth. To investigate long-term cover crop effects, trees grown with cover crop for 2 yr were transitioned to a standard herbicide practice. After 4 yr, trees in the initial 2 yr cover crop plots were 1 yr behind in growth compared to trees grown in bare rows for all 4 yr. Most growth reduction occurred in the first year following transplant. Additional borer losses of 1-2% per year were observed in production years 3 and 4. A second experiment answered 2 questions: Can killing the cover crop once it reaches maximal height protect trees from borers while also reducing competition and thereby increase tree growth? and Do herbicide applications increase borer attacks? In this experiment, red maples were grown with (i) a standard herbicide program, (ii) a mulch mat, (iii) a cover crop that was killed early, or (iv) a cover crop allowed to senesce naturally. Evaluations after 2 yr indicated early kill of the cover crop was not enough to improve tree growth. Further, trees in the early kill cover crop treatment had the most FAB attacks. Cover crops allowed to senesce naturally reduced FAB attacks in both studies; however, more work is needed to minimize disparities in tree growth during the initial year post-transplant and determine the causal relationship between herbicide use and borer attacks.

Cover crop composition in long‐term no‐till soils in semi‐arid environments do not influence soil health measurements after one year

AbstractEvaluating the influence of grass or broadleaf cover crops on soil health measurements is common in the northern US Midwest. However, the comparison among different cover crop mixtures, including blends of both grass and broadleaf species is limited. In 2018–2020, cover crop experiments were conducted in South Dakota at 11 site‐years. Cover crops were planted in the summer after small grains harvest as mixtures of dominantly grasses or broadleaves, a 50/50 grass/broadleaf mixture, and a no cover crop control. Soil and above‐ground plant residue samples were collected in the fall before winter termination and in the spring before corn planting. Soil samples were analyzed for permanganate oxidizable carbon, potentially mineralizable nitrogen, and soil respiration. Fall and spring above‐ground plant biomass in the cover crop plots were similar to the no cover crop control plots in seven of 11 site‐years. Thus, growing cover crop mixes may accelerate decomposition of above‐ground plant residue, possibly due to higher microbial diversity and activity under cover crops. However, including cover crops regardless of the mixture did not improve selected biological soil health indicators. Weather and soil properties (precipitation, soil organic matter, and pH) were related to differences in soil health measurements among site‐years. Overall, in the first year of planting a multi‐species mixture of grasses and/or broadleaves after small grain harvest, growers should not expect to find differences in soil health measurements. Long‐term trials are needed to determine whether these different cover crop mixtures change soil health over time.

No-till cover crop effects on the thermal properties of a Paleudult

Soil thermal properties play an important role in crop productivity, but the influence of a multi-species cover crops (CCs) on these properties are not well understood. This study evaluated the effects of no-till CCs (winter wheat [Triticum aestivum L.], crimson clover [Trifolium incarnatum L.], triticale [Triticale hexaploide Lart], hairy vetch [Vicia villosa], oats [Avena sativa], and cereal rye [Secale cereale L.]) on soil physical (bulk density [BD], and volumetric water content [ϴ] at 0, −33, and −100 kPa soil water pressures) and thermal properties (thermal conductivity [λ], volumetric heat capacity [CV], and thermal diffusivity [D]). Soil samples were collected just before CC termination at 0–10, 10–20, and 20–30 cm depths from CC and no cover crop (NC) plots during 2021 and 2022. Results showed that, after 2 years, CCs reduced BD by 17% and increased ϴ at 0, − 33, and − 100 kPa soil water pressures by 23%, 25%, and 28%, respectively relative to NC management. Thus, λ under NC was 16%, 19%, and 20% higher at 0, − 33, and − 100 kPa soil water pressures, respectively, compared with CC management. Conversely, CV was 17%, 14%, and 15% higher under CC compared with NC management at 0, − 33, and − 100 kPa soil water pressures. Regression analysis further demonstrated that while plant root was the most important factor influencing λ at saturation, ϴ played the greatest role in λ at other soil water pressures. Expectedly, ϴ was the most important factor influencing CV at all measured soil water pressures. Conclusively, no-till CCs can improve laboratory measured soil thermal properties by moderating heat transfer.

Influence of Recurrent Rolling/Crimping of a Cereal Rye/Crimson Clover Cover Crop on No-Till Bush Bean Yield

A no-till experiment was conducted in Auburn, AL U.S.A. to evaluate the effectiveness of an experimental two-stage roller/crimper in reoccurring rolling over the same area planted with a cereal rye/crimson clover cover crop mix and its influence on bush bean yield. Cover crop termination was much greater with rolling/crimping when compared to the non-rolled (untreated) control. During the three growing seasons, rolling three times had significantly higher termination rates compared to all other treatments, exceeding 90% in 2020. These results suggest that there may be an advantage to rolling/crimping three times so that planting of the cash crop could potentially be performed one week earlier, under favorable soil moisture conditions. However, for growing seasons 2018 and 2020 at three weeks after rolling, there were no differences between rolling treatments. In 2019, rolling three times over the same cover crop area was the only treatment that achieved above 90% termination rate indicating a clear advantage of recurring rolling/crimping in 2019. Rolling/crimping proved to be effective as yield was significantly higher compared to not rolled when averaged over all three growing seasons. This is possible due to the difficulty in planting into a standing cover crop which could have negative effects on seed to soil contact, but more importantly explained with the slight soil moisture advantage given to the rolled plots over the standing cover crop plots. Thus, optimum soil moisture when planting beans is key for successful germination and good main crop stand.

Winter Cover Crops Reduce Spring Emergence and Egg Deposition of Overwintering Navel Orangeworm (Lepidoptera: Pyralidae) in Almonds.

Habitat diversification has been shown to positively influence a variety of ecosystem services to agriculture, including biological control of arthropod pests. The impact of increased biodiversity tends to be species specific though, and practices therefore need to be developed on a case-by-case basis for each cropping system. In perennial systems, numerous studies have demonstrated that cover crops can have positive impacts on soil quality and other ecosystem services, such as pollination and pest management. However, few studies have focused on the use of cover crops to enhance pest control in almond orchards, especially winter cover crops. The primary pest of almonds in North America is navel orangeworm, Amyelois transitella Walker, which overwinter as larva or pupa on remnant nuts, many of which remain on the orchard soil surface. In the spring, first flight adults subsequently use these remnant nuts as reproductive substrate. An experiment was conducted to evaluate the influence of two distinct winter cover crop mixtures on overwintering mortality and spring egg deposition of A. transitella. Remnant nuts placed into cover crop plots produced fewer adult A. transitella in the spring, suggesting increased overwintering mortality. Additionally, spring egg deposition was reduced on remnant nuts in the cover crops, possibly due to the ground covers interfering with host location and access. In this way, winter cover crops appear to contribute to the reduction of A. transitella populations in the orchard by altering abiotic and physical conditions, although studies to document specific mechanisms are still needed.

Areawide management of fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), using selected cover crop plants

BackgroundFall armyworm, Spodoptera frugiperda (J. E. Smith) is a migratory moth that annually migrates northward each spring from sites in southern Florida and southern Texas. This caterpillar pest feeds on and damages row, turf and vegetable crops in the eastern and central U.S. Before migrating in spring, it feeds on cover crops in central and eastern Florida and expands its populations. Our objective was to use multi-year studies to compare fall armyworm populations that develop in cover crop plants.MethodsA series of field experiments and a laboratory feeding study were conducted to compare infestation and feeding and of fall armyworm on different cover crop plants. Field experiments had plots planted with corn (Zea mays L.), sorghum-sudangrass [Sorghum bicolor (L.) Moench], a standard cover crop in Florida, and two alternative cover crops, sunn hemp (Crotalaria juncea L.) and cowpea [Vigna unguiculata (L.) Walpers spp. unguiculata]. Another trial compared populations in sorghum-sudangrass and in mixtures of sorghum-sudangrass with buckwheat (Fagopyrum esculentum Moench) or pearl millet (Cenchrus americanus (L.) Morrone). Fall armyworm larvae were fed and allowed to develop on different sunn hemp germplasm in a laboratory trial.ResultsField populations of fall armyworm were highest on corn, followed by sorghum-sudangrass. Sunn hemp and cowpea had larval populations 70–96% less than on sorghum-sudangrass, suggesting replacement of this cover crop with either plant species might help reduce areawide populations of resident or migratory fall armyworm. Larvae collected from cover crop plots had parasitism levels that averaged 30%, with Chelonus insularis (Hymenoptera: Braconidae) emerging as the most commonly-collected species. Larval feeding on different sunn hemp germplasm lines resulted in no difference in weight gain.ConclusionsReplacing sorghum-sudangrass with sunn hemp varieties or germplasm should be acceptable as a replacement cover crop for areawide management of fall armyworm.

Shifts in bacterial community in response to conservation management practices within a soybean production system

A 3-year field study was conducted to assess effects of two winter cover crops, Elbon rye (Secale cereal L.) and Crimson clover (Trifolium incarnatum L.), under till and no till management, on bacterial community composition in soybean (Glycine max L.) field soils using high-throughput sequencing of the 16S rRNA gene. Effects of tillage and cover crop on bacterial composition at the phylum level were minor, with most significant differences between treatments occurring at finer taxonomic levels. Tilled plots displayed higher levels of Xanthomonadaceae, while cover cropped soils had greater Bradyrhizobium abundances. Functional gene prediction indicated that genes associated with decomposition of C and P compounds, as well as biocontrol agents, were elevated in tilled plots, genes associated with root growth promotion were elevated in cover crop treatments, and nitrate reductase and denitrification genes were elevated in both no till and cover crop plots. While valuable functional insights can be gained from sequence analyses, not all differences observed at the sequencing level will translate into functional differences due to variation in gene expression, and further study is needed to validate which functions can be predicted from sequencing data.

Mungbean-maize rotation improved soil properties and maize yield in dryland

One of the conditions to improve maize yield in dryland areas is by improving soil properties. This paper reports on the improvement of soil properties and maize yield resulted from rotating mungbean and maize in two consecutive years. In the first year, mungbean was grown as a cover crop at different population densities (250,000, 375,000, and 500,000 plants ha−1) combined with desiccation times of 28 and 35 days after planting in April 2019. Two weeks after the desiccation, maize seeds were planted at a density of 9 plants per m2. In those cover crop plots and a control treatment without a cover crop. All the treatments were replicated three times and were arranged in a Randomized Block Design. Following the maize crops, mungbean was grown again (except in the control plots) from October to December 2019 at the same population densities as before, combined with two seed classes; stock seeds and extension seeds. The mungbean was harvested in mid-December 2019 and after biomass determination, the residue was incorporated into the treatment plots. In mid-January 2020, maize seeds were planted at the same population density as before in all plot treatments, including control plots. Soil properties were determined at 60 days after maize planting. The results revealed that nitrogen, phosphorous, and potassium in the soil increased substantially by 52.6, 282.9, and 110%, respectively after two years of the rotation. There was an average of 44.7% increase in maize yield resulted from the highest mungbean population density plots as compared to the control treatment. It is concluded that mungbean-maize rotation is an effective way to improve maize yield in dryland areas.

Comparison of Bee Composition in Sunn Hemp and Other Cover Crops

Cover crops can be planted in rotation with cash crops to improve soils, assist in weed growth prevention, and help suppress plant pathogenic nematode populations. Experiments were conducted in northern and north-central Florida to evaluate bee populations within cover crop plants, including sunn hemp (Crotalaria juncea L.), sorghum-sudangrass (Sorghum bicolor [L.] Moench × S. bicolor var. sudanense [Piper] Stapf.), and cowpea (Vigna unguiculata [L.] Walp.). Almost 150 bees in 10 species and over 700 bees in 15 species were collected in pan (bee bowls) and blue vane traps, respectively. Both sets of traps captured bees from within all cover crop plots, indicating that these bees forage in disturbed habitats. The dominant bees collected, Melissodes spp., are ground-nesting solitary bees which may have been utilizing the ground below the plants and the border plot areas as a nesting site. Only a subset of the species composition associated with the cover crops was relevant to the pollination of sunn hemp, which requires large-bodied bees such as species of Xylocopa and Megachile.

Anisotropy of subsoil pore characteristics and hydraulic conductivity as affected by compaction and cover crop treatments

AbstractThe natural and cover crop (CC)‐induced anisotropy of subsoil pore characteristics is important in assessments of soil compaction but, until recently, has received limited attention. This study aims to quantify the anisotropy of soil pore characteristics and hydraulic conductivity in subsoils subjected to compaction and CC treatments in a split‐plot field experiment on temperate sandy loam soils. The main factor was ±compaction and the split‐plot factor was ±CC with fodder radish (Raphanus sativus L.). The compacted plots were heavily trafficked for 4 yr (2010–2013). After 4 yr under CC (2013–2016), core samples were collected at 0.3 m. The samples were taken vertically and horizontally to quantify the anisotropy of air‐filled porosity (εa) and air permeability (ka), saturated hydraulic conductivity (ksat), and bulk density (ρb). The results showed isotropic behavior for ρb and εa and significant anisotropic behavior (p &lt; .05) for ka, pore geometry index (PO1) (ka/εa), ratio of non‐Darcian to Darcian ka (R‐ratio), and ksat. For parameters with significant anisotropy, higher values occurred vertically than horizontally for all compaction –CC combinations, except for R‐ratio. This indicates that pre‐existing vertical continuous pores dominated the pore system in the control subsoil. A nonsignificant trend of higher values of ka, PO1, and ksat in the +CC than in the compacted –CC plots suggest that CC could contribute to the formation of vertical biopores. Including an autumn CC in rotation with a summer cereal crop for a longer period may significantly affect the anisotropy of the soil pore and hydraulic properties.

Influence of rye cover cropping on denitrification potential and year-round field N2O emissions

Cover cropping is beneficial for reducing soil erosion and nutrient losses, but there are conflicting reports on how cover cropping affects emissions of nitrous oxide (N2O), a potent greenhouse gas. In this study, we measured N2O fluxes over a full year in Illinois corn plots with and without rye cover crop. We compared these year-round measurements to N2O emissions predicted by the Intergovernmental Panel on Climate Change (IPCC) Tier 1 equation and the Denitrification-Decomposition (DNDC) model. In addition, we measured potential denitrification and N2O production rates. The field measurements showed typical N2O peaks shortly after fertilizer application, as well as a significant late-winter peak. Cover cropping significantly reduced all peak N2O fluxes, with decreases ranging from 39 to 95%. Neither model was able to accurately predict annual N2O fluxes or the decrease in N2O emissions from cover-cropped fields. In contrast to field measurements, lab assays found that cover cropping significantly increased potential denitrification by 90–127% and potential N2O production by 54–106%. The rye cover-cropped plots had lower soil nitrate and higher soil carbon. When limiting nitrate and excess carbon were provided in lab assays, the proportion of N2O resulting from denitrification decreased. These results suggest that the discrepancy between the observed decrease in field N2O emissions and the increase in denitrification potential may be due to the difference in available nutrients between the field and laboratory measurements. Overall, these results suggest the importance of late-winter peaks in N2O emissions and the potential of rye cover cropping to reduce N2O emissions from agricultural fields.

Responses of soil microbial community structure and greenhouse gas fluxes to crop rotations that include winter cover crops

Agricultural crop diversity has the potential to alter soil microbial communities and greenhouse gas (GHG) emissions. To test this hypothesis, we conducted a field study on silty clay loam soil in south-east South Dakota under two crop rotations; 2-yr, maize (Zea mays L.)-soybean (Glycine max L.) and 4-yr, maize-soybean-oat (Avena sativa)-winter wheat (Triticum aestivum) managed with a winter cover crop and fallow management under no-till system. Phospholipid fatty acid (PLFAs) profiles were used to assess relative abundance of broad taxonomic groups of soil microorganisms in four active growing seasons. The static chamber technique was used to weekly monitor CO2, CH4, N2O fluxes during the growing seasons of maize and soybean phases in 2017 and 2018, respectively. Total PLFAs and relative abundance of total bacterial and fungal biomass were not affected by the treatments within the sampling event. However, averaged over the study period, the total PLFAs and abundance of total bacterial biomass as well as their sub-groups (Gm+, Gm–, and actinomycetes) were statistically greater with the 4-yr rotation as compared to the 2-yr rotation, whereas, there was no difference between cover crop and fallow plots. Regardless of cover cropping management, the 2-yr rotation had greater CO2 emissions than the 4-yr during the 2017 growing season. However, the 4-yr rotation increased the GHG fluxes during spring thaw of 2018, whereas, its effect was convoluted with cover cropping system (i.e. interaction effect) for summer and fall sampling dates. Cumulative CO2 tended to be greater under cover crop than the fallow when averaged over rotations during 2017 (p = 0.106), however, significant interaction effect during 2018 suggested that cover crops had lower CO2 emissions than the fallow under 2-yr rotation (p = 0.009). This study suggests that cropping system diversification achieved by extending length of rotations through small grains and by growing winter cover crops such as winter rye under no-till system has the potential to alter microbial community composition and mitigate GHG emissions.

Soil water dynamics under a warm-season cover crop mixture in continuous wheat

Cover crop technology can potentially benefit monoculture wheat systems in the semi-arid US Southern Great Plains, but the biggest hurdle in such regions where evapotranspiration exceeds precipitation is soil water. Cover crop impact on soil water use and availability is a major cause for concern in water-limited environments. The objective of this study was to evaluate the impact of cover crops, grazing, and intercrops on soil water dynamics under rainfed conditions. Seven treatments were evaluated, including conventional tillage (CT) and combinations of no-tillage (NT) with a cover crop mixture, grazed cover crops, and/or cash crop intercropping. The three-year study was conducted on a long-term NT continuous wheat system in the Texas Rolling Plains. Despite dry periods, the cover crop mixture produced 2141 to 3503 kg ha−1 dry herbage mass. Stored soil water was significantly lower within 60 days after planting for cover crop compared to no cover crop treatments. Stored soil water was 22–26% lower in cover crop plots at time of termination. In the final two years of the study, the positive change in stored soil water from cover crop termination to wheat planting was two to four times greater for cover crop treatments compared to non-cover crop treatments. The greater infiltration and water capture after termination has the potential to make up for the loss in soil water that cover crops used.

Cover Image, Volume 49, Issue 2

On the cover: Collecting soil nitrate samples in a recently terminated cover crop plot. See Waring et al., “Influence of no‐till and a winter rye cover crop on nitrate losses from tile‐drained row‐crop agriculture in Iowa,” https://doi.org/10.1002/jeq2.20056. Photo by Emily R. Waring. image

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

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