Integrating cover crops (CC) in rotations provides multiple ecological services, but it must be ensured that management does not increase pre-emptive competition with the subsequent crop. This ...experiment was conducted to study the effect of kill date on: (i) CC growth and N content; (ii) the chemical composition of residues; (iii) soil inorganic N and potentially mineralizable N; and (iv) soil water content. Treatments were fallow and a CC mixture of barley (Hordeum vulgare L.) and vetch (Vicia sativa L.) sown in October and killed on two different dates in spring. Above-ground biomass and chemical composition of CC were determined at harvest, and ground cover was monitored based on digital image analysis. Soil mineral N was determined before sowing and after killing the CC, and potentially mineralizable N was measured by aerobic incubation at the end of the experiment. Soil water content was monitored daily to a depth of 1.1 m using capacitance sensors. Under the present conditions of high N availability, delaying kill date increased barley above-ground biomass and N uptake from deep soil layers; little differences were observed in vetch. Postponing kill date increased the C/N ratio and the fiber content of plant residues. Ground cover reached >80% by the first kill date (∼1250°C days). Kill date was a means to control soil inorganic N by balancing the N retained in the residue and soil, and showed promise for mitigating N losses. The early kill date decreased the risk of water and N pre-emptive competition by reducing soil depletion, preserving rain harvested between kill dates and allowing more time for N release in spring. The soil potentially mineralizable N was enhanced by the CC and kill date delay. Therefore kill date is a crucial management variable for maximizing the CC benefits in agricultural systems.
In this study, field-specific data was collected from a 10-year experiment in central Spain in which vetch (Vicia sp. L.) and barley (Hordeum vulgare L.) were established as cover crops and compared ...to the traditional fall-winter fallow between two irrigated cash crops, maize (Zea mays L.) and sunflower (Helianthus annuus L.). The global warming potential (GWP) balance included direct and indirect (nitrous oxide (N2O) resulting from the deposition of ammonia (NH3) or from leached nitrate (NO3−)) soil greenhouse gas (GHG) emissions, changes in soil organic carbon (SOC) and albedo, and carbon dioxide equivalent (CO2eq) emissions from inputs, irrigation and farm operations. Several scenarios involving i) changes in the termination method of the cover crops, ii) consideration of the application of a distinct nitrogen (N) source (urea, slurry or manure instead of ammonium nitrate) or nitrification inhibitors, iii) employing the same N rate for all treatments (i.e., conventional instead of integrated fertilization), iv) modelling SOC accumulation over a 100-year horizon, and v) using default emission factors, were also analysed. Under the conditions of our experiment, cover crops mitigated yield-scaled emissions by 77.4% (barley) and 91.9% (vetch). Synthetic N fertilization (particularly the industrial production of fertilizer) contributed 38% to the balance of the cover cropping treatments, followed by SOC (22.5%), irrigation (14.7%) and albedo (14.5%). All scenarios led to notable mitigation efficacies, ranging from 39% mitigation (in barley when considering default or non-specific emission factors) to a net CO2eq sink (i.e., >100% mitigation) in the scenario consisting of the replacement of ammonium nitrate by urea or organic fertilizers although with side effects on NH3 volatilization and/or yields. Based on these results, the combined use of cover cropping and integrated soil fertility management could lead to the design of C-neutral irrigated cropping systems in semi-arid regions.
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•Vetch and barley as cover crops abated net GWP by 90% and 75%, respectively, in comparison to fallow.•Synthetic N fertilization (particularly the industrial production) contributed 38% to GWP.•Soil organic C, albedo change and irrigation were also important GWP components.•All scenarios led to notable mitigation efficacies, ranging from 39% to a net CO2eq sink.•Improving N management enhanced the GWP mitigation potential of cover crops.
Introducing cover crops in irrigated areas may play a relevant role in providing ecosystem services such as erosion control, clean water and mitigation of soil degradation. Our objective was to ...determine the effect of replacing the traditional winter fallow in crop rotations of irrigated semi-arid areas by a cover crop on organic C and N sequestration, aggregate stability, water infiltration, and nitrate leaching. The study was conducted comparing barley (Hordeum vulgare L.) and vetch (Vicia sp. L.) cover crops to the fallow over the course of 10 years, with most variables measured every other year. Compared to the fallow, cover crops promoted C sequestration at a rate of 180 kg C ha−1 year−1 and N retention at a rate of 13 kg N ha−1 year−1. By the end of the experiment, the barley cover crop had enhanced the soil structural stability, the water holding capacity, the infiltration rate and the saturated hydraulic conductivity with respect to those characteristics in the fallow, with the vetch treatment having an intermediate effect. Compared to the fallow, barley mitigated the nitrate leaching risk by reducing inorganic N content in the top 4 m of the soil profile. Improvements in C and N stocks and soil and water quality may be attained by using cover crops in degraded soils.
•Cover crops promote soil carbon sequestration at an annual rate of 180 kg C ha−1•Cover crops promote nitrogen retention at an annual rate of 13 kg N ha−1•Barley enhanced soil structural stability and infiltration with respect to the fallow•Soil properties improvement by the vetch was intermediate between barley and fallow•Nitrate leaching mitigation by the barley was related to reduction in N surplus
Cover crops (CC) can be used to reduce soil inorganic N (SIN) losses from agricultural soils. However, challenges exist in establishing CCs after corn (Zea mays L.) harvest in regions with a limited ...window for fall CC growth. One solution to this constraint is to establish a CC by interseeding into a standing corn crop. This experiment aims to assess the effect of interseeding CCs on the N cycle. Within organically managed corn grain and silage systems, we implemented three CC treatments: interseeded annual ryegrass (Lolium multiflorum Lam.), postharvest seeded cereal rye (Secale cereale L.), and a no‐CC fallow. We applied fertilizer at a standard level (336 kg N ha−1) and at a high level (420 kg N ha−1). Silage was harvested in October and grain in November. Corn yields were not affected by CC treatments. In the fall in the silage system, the interseeded treatment had reduced SIN compared with the postharvest seeded treatment. In the spring, both interseeded and postharvest seeded treatments had less deep SIN than fallow in grain and silage. Under high N conditions in the spring, interseeded treatments had greater microbial biomass than all other treatment combinations. Both CC treatments and applied N levels affected microbial taxonomic groups. In terms of N retention services, interseeded CCs do have potential to outperform a postharvest seeded CC with a longer window for unshaded fall growth (as in a silage system) and may perform just as well as a postharvest seeded CC in the spring.
Core Ideas
Interseeded annual ryegrass CC can retain SIN in corn systems.
In late fall in a corn silage system, interseeded CC treatments had reduced surface SIN.
In spring, interseeded CC and postharvest cereal rye CC treatments had less deep SIN than a no‐CC treatment.
Soil microbial biomass was greatest in interseeded systems under high SIN conditions.
Maximizing time for unshaded fall interseeded CC growth may increase N retention in corn systems.
•Reduction of soil strength by cover crops was not consistent within the year.•On an annual base cover crops affected soil strength by modifying soil water content.•Barley mulch increased water ...content, thus reducing soil strength before maize sowing.•The grass barley cover crop reduced soil strength more than legume vetch.•A combination of cover crops and reduced tillage diminished the risk of soil crusting.
Replacement of bare fallow in rotations by cover crops is a promising tool to reduce crusting, although the interactions with the soil moisture and the effect of the cover crop species are still not well understood. The objective of this work was to determine how cover crops modify the soil surface response to penetration and their relation with the soil water content. Two winter cover crops, barley (Hordeum vulgare L.) and vetch (Vicia sp. L.), were compared with a bare fallow treatment in a 10-year field experiment in central Spain. Soil resistance to penetration and soil water content were intensively measured (76 sampling dates) at two surface depths, using two types of surface penetrometers. Under the barley cover crop, the number of very dry events was reduced by around 20%, compared to the bare fallow. The soil resistance to penetration was closely related to the surface soil water content (R2 = 0.65) and cover crops affected it through soil moisture modification. In this line, the greater mulch provided by barley cover crop respect to vetch, increased the soil water content prior to main crop seeding, resulting in less resistance to penetration during this critical period. The good performance of barley resulted in a reduction of more than 60% of the soil resistance to penetration between the 3rd and 8th year of the experiment (7.2–2.9 kg cm−2, respectively). Even under bare fallow, soil strength was decreased after ten years with reduced tillage. Therefore, the maintenance of cover crop residues over surface soil together with reduced tillage enhanced the soil surface conditions and steadily reduced the risk of crust formation. Expected enhancement of main-crop germination, water infiltration, soil aeration and erosion mitigation may be attained by cover-cropping in degraded soils.
The termination date is recognized as a key management factor to enhance cover crops for multiple benefits and to avoid competition with the following cash crop. However, the optimum date depends on ...annual meteorological conditions, and climate variability induces uncertainty in a decision that needs to be taken every year. One of the most important cover crop benefits is reducing nitrate leaching, a major concern for irrigated agricultural systems and highly affected by the termination date. This study aimed to determine the effects of cover crops and their termination date on the water and N balances of an irrigated Mediterranean agroecosystem under present and future climate conditions. For that purpose, two field experiments were used for inverse calibration and validation of the WAVE model (Water and Agrochemicals in the soil and Vadose Environment), based on continuous soil water content data, soil nitrogen content and crop measurements. The calibrated and validated model was subsequently used in advanced scenario analysis under present and climate change conditions. Under present conditions, a late termination date increased cover crop biomass and subsequently soil water and N depletion. Hence, preemptive competition risk with the main crop was enhanced, but a reduction of nitrate leaching also occurred. The hypothetical planting date of the following cash crop was also an important tool to reduce preemptive competition. Under climate change conditions, the simulations showed that the termination date will be even more important to reduce preemptive competition and nitrate leaching.
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•WAVE model was inverse calibrated and validated with field measurements.•Impact response surface approach was used to assess future climate scenarios.•Late cover crop termination reduced leaching but increased competition risk.•The cash crop planting date was a tool to control preemptive competition.•Under climate change conditions, cover crop management becomes crucial.
•The crop diversification technique of cover crop interseeding was tested in a Mediterranean region.•Nine species were interseeded into irrigated maize and compared to autumn cover crops.•Ryegrass, ...common vetch, yellow sweetclover and barrel medic were the most suitable species.•Maize grain yield and quality were not affected by interseeded crops.•Interseeded crops lengthened cover crop benefits compared to autumn cover crops.
Cover crop (CC) benefits and adoption in crop rotations may be limited by the short planting window after the cash crop. Interseeding or relay intercropping of CC is a technique that could overcome short planting windows constraints and allow CC establishment and growth. However, in Mediterranean regions this technique has been poorly implemented.
Field experiments were established in Central Spain during two consecutive growing seasons to assess the performance of different species as interseeded crops into irrigated maize (Zea mays L.). The treatments included annual ryegrass (Lolium multiflorum L.) and eight legumes: burr medic (Medicago polymorpha L.), barrel medic (Medicago truncatula L.), yellow sweetclover (Melilotus officinalis L.), berseem clover (Trifolium alexandrinum L.), balansa clover (Trifolium michelanium L.), red clover (Trifolium pratense L.), Persian clover (Trifolium resupinatum L.), and common vetch (Vicia sativa L.). A bare soil was included as control treatment. After the maize harvest, the four species with the best performance were planted as autumn cover crops in adjacent plots. The ground cover was studied throughout the experimental period, and biomass and N content for each species were determined in the autumn and in the following spring prior to the cover crop termination. The soil inorganic N content was determined in spring.
Barrel medic, yellow sweetclover, common vetch and annual ryegrass were the species with the best performance in terms of soil coverage during the summer. Red clover and Persian clover had good establishment in one out of two years. None of the interseeded species impaired maize grain yield or quality. Interseeded species achieved better soil coverage and increased the biomass accrued at autumn compared to cover crops sown in October. Therefore, interseeded species ensured longer ground coverage, increasing the potential for soil quality improvement or weed suppression. Moreover, the higher biomass achieved by interseeded species ensured the survival of yellow sweetclover, which was winter killed when planted in the autumn. Interseeded cover crops enhanced the potential of N leaching reduction compared to autumn cover crops.
This experiment confirms the suitability of different species interseeded in summer into irrigated maize in Mediterranean regions, and highlights the extra benefits of this practice in annual rotations.
Cover crops (CC) are biological tools with a great potential for weed control, but the suppression level depends on the CC species and management. A 2-year study was performed in the eighth year of a ...long-term experiment located in Central Spain to study the effect of replacing winter fallow by barley (Hordeum vulgare L.) or vetch (Vicia sativa L.), on the weed control. Moreover, two CC termination dates were evaluated. Weed biomass, density, diversity, population composition and the seed bank were assessed. Ground cover and CC biomass, soil inorganic N and topsoil water content were determined throughout the season. Barley achieved a greater weed control compared to vetch in winter and early spring. Later in May, both CC residues decreased weed density compared to fallow (63% in 2015, 55% in 2016), and reduced the density of some broadleaf species (i.e. Xanthium spinosum L. reduced >50%). The weed seedbank density was not affected by CC but the effect on specific species confirmed the control over Xanthium spp. (78% reduction), and also warned of the incomplete weed control by CC. The year in which the biomass and ground cover increased between termination dates, delaying the CC termination reduced weed density >75%. Therefore, delaying the termination date was a mean to increase weed control but should be performed with caution to avoid pre-emptive competition with the cash crop. Results underline the relevance of CC species and the termination date as management tools for weed control, and must be considered to plan specific management strategies in different scenarios.
•Barley cover crop reduced weed density and diversity during the cropping period.•In spring, barley and vetch mulch residues reduced weed density by 51–63%.•Weed diversity and community composition were influenced by winter cover crops.•After 10-years with cover crops, total seedbank density and diversity were not affected.•Delaying the cover crop termination date reduced weed density in one of the years.
•The roller-crimper termination enhanced soil water conservation in early spring.•The tillage termination was more dependent on summer post-emergence labors.•The roller-crimper reduced energy ...consumption compared to tillage termination.•Roller-crimper main constraint was the risk of poor cover crop termination.
The use of winter cover crops (CCs) in annual rotations is a tool to increase agroecosystem sustainability. To optimize their benefits, the choice of how to terminate CCs in spring is crucial, because this decision may lead to differences in soil–plant variables and affect cash crop productivity. The use of a roller-crimper is an emerging option in both conservation and organic agriculture but its adoption in Mediterranean regions is still rare.
In this work the objective was to identify best CC termination practices to maximize benefits and increase agro-ecosystem resilience. To this end a field experiment with a barley/vetch (Hordeum vulgare L. / Vicia villosa L.) CC mixture followed by an irrigated corn (Zea mays L.) was conducted in Central Spain in three consecutive years. Each year, three CC termination methods (roller-crimper, glyphosate + roller-crimper, and CC residue incorporation) and four post-emergence operations to reduce weed pressure in summer (post-emergence herbicide, inter-row cultivator, the combination of the two, or without operation) were compared. The effect on the spring soil water content and temperature, weed control, soil inorganic N and the corn grain yield and N content were evaluated. Energy and economic analyses were conducted.
An ineffective CC termination by roller-crimper was overcome when using glyphosate or post-emergence herbicides. However, the roller-crimper was less dependent on post-emergence operations than residue incorporation to achieve proper weed control and attain good productivity. The results showed that in early corn growth stages, roller-crimper use enhanced the soil’s water conservation and decreased soil temperature compared to CC residue incorporation. Moreover, the energy cost was lower for roller-crimper termination. Our findings suggest that the roller-crimper increases the environmental sustainability in Mediterranean regions, but farmers may encounter economic risks. Further research is needed to find proper conditions that maximize the potential of this CC termination method under Mediterranean conditions.
We describe herein the synthesis and neuroprotective capacity of an array of 31 compounds comprising quinolyloximes, quinolylhydrazones, quinolylimines, QNs, and related heterocyclic azolylnitrones. ...Neuronal cultures subjected to oxygen-glucose deprivation (OGD), as experimental model for ischemic conditions, were treated with our molecules at the onset of recovery period after OGD and showed that most of these QNs, but not the azo molecules, improved neuronal viability 24 h after recovery. Especially, QN ( Z)- N-tert-butyl-1-(2-chloro-6-methoxyquinolin-3-yl)methanimine oxide (23) was shown as a very potent neuroprotective agent. Antioxidant analysis based on the ability of QN 23 to trap different types of toxic radical oxygenated species supported and confirmed its strong neuroprotective capacity. Finally, QN 23 showed also neuroprotection induction in two in vivo models of cerebral ischemia, decreasing neuronal death and reducing infarct size, allowing us to conclude that QN 23 can be considered as new lead-compound for ischemic stroke treatment.
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