Cover Crop Management Research Articles

Rotational no‐till and tillage‐based organic corn produce management tradeoffs in the Northeast

AbstractReducing the intensity and frequency of tillage in organic grain production systems is likely to produce several agronomic, economic, and environmental tradeoffs. We evaluated four organic corn (Zea mays L.) sequences in a 3‐yr, full‐entry organic cropping systems experiment. Two sequences included a hairy vetch (Vicia villosa Roth)/triticale (Triticale hexaploide Lart.) mixture sown after spelt harvest that differed in tillage practices (no‐till [NT], conventional) before corn and corn harvest management (silage, grain). Two sequences included a red clover (Trifolium pretense L.)/timothy (Phleum pretense L.) mixture frost‐seeded into spelt in late winter followed by conventional tillage preceding corn and either silage or grain harvest. Our results showed that late‐season weed biomass did not differ across alternative sequences, although both tillage and NT corn production resulted in high in‐row weed pressure in different years. Cover crop management prior to tillage‐based corn production did not affect grain yields, but NT silage production resulted in lower yields compared with the tilled sequence. Corn silage yields were positively correlated with corn populations in both tilled and NT systems. The NT sequence lowered tillage frequency and intensity by 39 and 52%, respectively, compared with tillage‐based corn production as measured using established metrics, including the soil disturbance rating, but did not significantly influence labile carbon pools. Sequences using underseeded red clover resulted in higher net returns compared with hairy vetch sequences due to additional income from fall forage harvests.

Cover crop species can increase or decrease the fertilizer‐nitrogen requirement in maize

AbstractCover crop species and termination date could affect fertilizer‐nitrogen (N) management and N diagnostic methods traditionally used in bare fallow‐maize (Zea mays L.) systems. Our objectives were to (a) assess the effect of cover crop termination date on maize yield and response to fertilizer‐N, (b) determine maize yield at varying N rates following different cover crop species and mixtures, and (c) evaluate the chlorophyll meter reading (CMR), grain N concentration (Nc), and grain N nutrition index (NNI) as N diagnostic methods. Experiments were conducted at four sites in the southeastern Argentinean Pampas with maize planted after cover crops. Factors investigated were cover crops with vetch (Vicia villosa Roth), vetch–oat (Avena sativa L.) mixture, or bare fallow; early termination of cover crops or ∼3 wk later; and maize fertilizer‐N at 0, 50, 100, and 200 kg N ha–1. The minimum N rate that maximized grain yield was higher in vetch–oat mixture (100 kg N ha–1) than in vetch (50 kg N ha–1). Maize yield was not affected by cover crops with 200 kg N ha–1. Late termination dates of vetch–oat mixture reduced maize yield by 15% compared with early termination dates, while there was no effect of vetch termination date. Cover crop termination date did not affect yield response to fertilizer‐N. Relative CMR at silking, grain Nc, and especially grain NNI at maturity were useful tools to diagnose maize N status and cover crop effect. Cover crop management should be considered to adjust the fertilizer N rate and optimize maize productivity.

Implications of cover crop planting and termination timing on rainfed maize production in semi-arid cropping systems

• Introducing cover crops in a rainfed wheat-maize-fallow rotation of semi-arid regions. • Cover crops induced nitrogen immobilization when terminated late in the spring. • Late terminated cover crops suppressed weeds early in the maize growing season. • Late terminated cover crops did not affect soil carbon and respiration. • Cover crops reduced maize grain yield regardless of the termination timing. Despite the potential to increase soil organic matter, cycle soil nutrients, and suppress weeds, there is a concern that cover crops (CCs) soil water use negatively impacts subsequent crops in water-limited environments. Cover crop management practices such as planting and termination timing may mitigate the detrimental impacts of CCs in semi-arid cropping systems. To determine the effects of CCs under water-limited environments, we evaluated the total CC biomass produced in the fall and spring, soil water content during the subsequent maize growing season, weed density and biomass, crop residue, and soil nutrients at the maize V6 development stage, and maize productivity. The experiment was conducted under a wheat-maize-fallow rotation at two sites (Grant and North Platte, NE) during 2016−2017 and 2017−2018. Treatments consisted of three planting timings after winter wheat harvest and three CC termination timings and fallow (no CCs) before maize establishment. Planting CCs shortly after winter wheat harvest increased CC biomass in the fall and early spring compared to late planting. Cover crops terminated early in the spring reduced weed biomass (−70 %), while CCs terminated late in the spring reduced both weed density (−56 %) and biomass (−82 %) compared to fallow. Due to above-normal precipitation during the experiment, soil water measured at 0−20 cm soil depth was impacted by CCs only at Grant 2016−2017. Cover crops terminated late in the spring increased crop residue biomass but decreased total nitrogen at 0−10 cm soil depth by 17 %, and decreased soil nitrate at the 10−20 cm soil depth up to 26 % compared to fallow. Cover crops planted late in the summer (August) and terminated late in the spring (May) had the most detrimental impact on maize grain yield. Late termination of CCs in the spring reduced corn grain yield by up to 20 % compared to fallow. Despite enhanced weed suppression and crop residue, CCs decreased soil nitrogen and maize grain yield, especially when terminated late in the spring. Producers in semi-arid regions of the Great Plains willing to incorporate CCs should use caution when selecting management strategies for their CCs to minimize maize grain yield and economic losses.

Strategies to terminate summer cover crops for weed management in no-tillage vegetable production in southeast Brazil

AbstractCover crop residue left on the soil surface as organic mulch in no-tillage crop production provides several environmental benefits, including weed suppression. Thus, many farmers who use cover crops attempt to reduce the use of agricultural inputs, especially herbicides. Therefore, our objectives were to study the potential of different cover crop species to suppress weeds and produce an in situ organic mulch and to evaluate the effect of the organic mulch with and without spraying glyphosate on weed suppression for vegetable (tomato [Solanum lycopersicumL.] and broccoli [Brassica oleraceaL. var.botrytis]) growth and yield. Five cover crop treatments (sunn hemp [Crotalaria junceaL.], jack bean [Canavalia ensiformis(L.) DC.], pearl millet [Pennisetum glaucum(L.) R. Br.], forage sorghum [Sorghum bicolor(L.) Moench ssp.bicolor], and no cover crop [control]) were used in the main plots; and glyphosate was or was not sprayed on the flattened cover crop in the subplots of this split-plot experimental design. Organic mulch from pearl millet, sorghum, and sunn hemp resulted in lower weed biomass during the early seasons of both tomato and broccoli than mulch from jack bean and no cover crop (control). Spraying glyphosate after roller-crimping reduced weed biomass by 103 g m−2and 20 g m−2by 45 and 60 d after transplanting (DATr) of tomato, respectively, and resulted in a better tomato yield compared with not spraying. Glyphosate reduced weed biomass by 110 g m−2in the early season of broccoli (30 DATr) but did not affect yield. Terminating high-biomass cover crops with a roller-crimper is a promising technique for weed management in vegetable crops that has the potential to reduce or even eliminate the need for herbicide.

Response of Cover Crops to Phytopythium vexans, Phytophthora nicotianae, and Rhizoctonia solani, Major Soilborne Pathogens of Woody Ornamentals

Management of plant diseases is a subject of concern for researchers as well as growers. Different management practices are being developed and used to combat the rising number of plant pathogens, which threaten nursery crop production. Use of cover crops for sustainable management of soilborne diseases is being explored as an alternative strategy to the chemicals. However, the potential threat of these cover crops acting as a secondary host of these devastating soilborne pathogens has not been described. We studied the response of the major cover crops being used by woody ornamental growers in the Southeastern United States to Phytopythium vexans, Phytophthora nicotianae, and Rhizoctonia solani in greenhouse conditions to identify the effective cover crops that can be used in a nursery field production system. Data related to post-emergence damping-off and plant growth parameters (plant height increase and fresh weight) were recorded. Similarly, cover crop roots were assessed for root rot disease severity using a scale of 0–100% roots affected. Among the tested cover crops, the grass cover crops triticale (×Triticosecale Wittm. ex A. Camus.), annual ryegrass (Lolium multiflorum L.), Japanese millet (Echinochloa esculenta (A. Braun) H. Scholz), and the legumes Austrian winter pea (Pisum sativum var. arvense (L.) Poir) and cowpea ‘Iron and Clay’ (Vigna unguiculata (L.) Walp.), showed lower root rot disease severity and post-emergence damping-off in the soil inoculated with P. nicotianae, R. solani, or P. vexans compared to the other crops. Since these cover crops can act as non-host crops and benefit the main crop in one way or another, they can be used in the production system. Further research is recommended to evaluate their performance in a natural field setting.

Organic fertility inputs synergistically increase denitrification-derived nitrous oxide emissions in agroecosystems.

Soil fertility in organic agriculture relies on microbial cycling of nutrient inputs from legume cover crops and animal manure. However, large quantities of labile carbon (C) and nitrogen (N) in these amendments may promote the production and emission of nitrous oxide (N2 O) from soils. Better ecological understanding of the N2 O emission controls may lead to new management strategies to reduce these emissions. We measured soil N2 O emission for two growing seasons in four corn-soybean-winter grain rotations with tillage, cover crop, and manure management variations typical of organic agriculture in temperate and humid North America. To identify N2 O production pathways and mitigation opportunities, we supplemented N2 O flux measurements with determinations of N2 O isotopomer composition and microbiological genomic DNA abundances in microplots where we manipulated cover crop and manure additions. The N input from legume-rich cover crops and manure prior to corn planting made the corn phase the main source of N2 O emissions, averaging 9.8kg/ha of N2 O-N and representing 80% of the 3-yr rotations' total emissions. Nitrous oxide emissions increased sharply when legume cover crop and manure inputs exceeded 1.8 and 4Mg/ha (dry matter), respectively. Removing the legume aboveground biomass before corn planting to prevent co-location of fresh biomass and manure decreased N2 O emissions by 60% during the corn phase. The co-occurrence of peak N2 O emission and high carbon dioxide emission suggests that oxygen (O2 ) consumption likely caused hypoxia and bacterial denitrification. This interpretation is supported by the N2 O site preference values trending towards denitrification during peak emissions with limited N2 O reduction, as revealed by the N2 O δ15 N and δ18 O and the decrease in clade I nosZ gene abundance following incorporation of cover crops and manure. Thus, accelerated microbial O2 consumption seems to be a critical control of N2 O emissions in systems with large additions of decomposable C and N substrates. Because many agricultural systems rely on combined fertility inputs from legumes and manures, our research suggests that controlling the rate and timing of organic input additions, as well as preventing the co-location of legume cover crops and manure, could mitigate N2 O emissions.

Research advances on cover crop plantation and its effects on subsequent crop and soil environment

Cover crops are grown in temporal and spatial gaps of agricultural production to reduce or avoid soil exposure. As it can protect farmland soil from wind erosion, water erosion and human disturbance, planting cover crops is considered as a new type of conservation tillage practice. Here, we briefly introduced the planting management of cover crops, including crop species, planting modes, and the returning to farmland after their termination, which could provide a reference for efficiently planting cover crops at large scale during the fallow period. Based on domestic and foreign studies, we summarized the benefits of cover crops on agroecosystem, including cash crops, soil quality, weed control, greenhouse gas emission, and soil microbes. Our review illustrated their importance in improving soil quality and achieving sustainable agricultural development, despite the limitation of cover crops, including unobvious benefits in the short-term and the reduction of crop yield caused by improper management.

Functional root trait‐based classification of cover crops to improve soil physical properties

AbstractCover crop use is a well‐established soil conservation technique and has been proven effective for erosion control and soil remediation in many arable systems. Whereas the obvious protection mechanism of cover crops occurs through the canopy, plant roots perform multiple functions. It is important to consider the soil functions delivered by different root systems in order to increase the uptake of cover crops for sustainable soil and water management. A classification of cover crop root systems up to 0.6 m deep based on functional traits will allow us to better study their potential role in soil bio‐engineering, soil structural improvements for hydrological services and soil resource protection. This was a glasshouse experiment, using large 1‐m3 containers filled with loam soil, loose topsoil and compacted subsoil, in which seven cover crop species (oat, rye, buckwheat, vetch, radish, mustard, phacelia) were grown for 90 days. Root cores were taken at the end of the experiment, washed and imaged to determine root traits (total root length density, average root diameter, root specific length and root surface area) for both the topsoil and subsoil layers. Root identity was determined from a distinctive combination of single root traits and related to three soil functional variables, representing soil structural improvement, runoff mitigation and erosion control. The results showed that total root length and root surface area correlate well with aggregate stability and soil macroporosity. Buckwheat, mustard and rye had significantly greater aggregate stability, as well as 10, 8 and 7% greater microporosity, respectively, at the interface with the compacted layer when compared to the control bare soil. Furthermore, average root diameter negatively correlated with soil macroporosity, indicating that cover crops with a fine root system are more beneficial for creating pore‐space than those with thicker taproots. Selecting cover crop species with the right root traits is therefore crucial to improve soil health.Highlights Roots of cover crops are a largely unexplored frontier for bio‐engineering of agricultural soils. Combinations of root traits were identified that most improve soil characteristics. Cover crops with finer root systems were better at enhancing porosity. Root length and surface area were most important for enhancing soil structure.

Sorghum cover crop and repeated soil fumigation for purple nutsedge management in tomato production.

Purple nutsedge (Cyperus rotundus L.) is one of the most common and troublesome weeds. Field research trials were conducted in Florida to evaluate the effects of repeated fumigation and a sorghum sudangrass [Sorghum bicolor S. bicolor var. sudanense (Piper) Stapf.] cover crop on purple nutsedge (Cyperus rotundus L.) populations over time in tomato (Solanum lycopersicum L.) production. Among the soil fumigants, DMDS + metam potassium was consistently the most effective treatment in terms of in-crop purple nutsedge control. Plots with a sorghum cover crop during the fallow period exhibited higher purple nutsedge density during the tomato growing season as well as higher purple nutsedge shoot and tuber densities during the fallow period compared to the chemical fallow. DMDS + metam potassium was the most effective fumigant for purple nutsedge control. Unexpectedly, a sorghum cover crop during the fallow period was less effective than chemical fallow for purple nutsedge management, and therefore we do not recommend the use of sorghum cover crops for weed management in fields where purple nutsedge is the major weed species.

Cover crop management in the maize-wheat offseason

This research studied a suitable cover crop considering biomass accumulation and nutrient cycling and its herbicide management to be adopted in the maize-wheat offseason as well as its influence on wheat yield. Experiment was laid out as a randomized block design in a factorial scheme with five cover crops (Fagopyrum esculentum, Crotalaria juncea, Pennisetum glaucum, Urochloa brizantha and Crotalaria spectabilis at 2017/18 growing season and at 2018/19, Fagopyrum esculentum and Crotalaria spectabilis were switched for Dolichos lablab) and two herbicide management (Desiccation 17 days before and at the wheat Sowing day) with four replications. Fallow was used as a control. Fagopyrum esculentum showed the fastest cycle and can be recommended for shorter offseason periods (50 days). Pennisetum glaucum showed the highest biomass yield at both years, standing out as the best option for offseason periods of 70 to 80 days. Tradeoff between the additional biomass produced by millet and brachiaria between herbicide desiccation periods does not cover the wheat grain yield reduction, suggesting that its herbicide management should be anticipated. On the other hand, Crotalarias showed a linear increase in biomass along the periods without wheat yield effects and its herbicide dissection at the wheat sowing day is recommended

Cover crops differentially influenced nitrogen and phosphorus loss in tile drainage and surface runoff from agricultural fields in Ohio, USA

Nitrogen (N) and phosphorus (P) loss from crop production agriculture is transported to adjacent and downstream water bodies, resulting in negative environmental impacts including harmful and nuisance algal blooms. Cover crops are a conservation management practice that replaces bare soil with vegetation outside of the cash crop growing season, purportedly reducing N and P loss by increasing water and nutrient demand in agroecosystems. In this study, we compared nitrate (NO3−-N), total N (TN), dissolved reactive P (DRP), and total P (TP) loads in subsurface (tile) drainage and surface runoff from fields with cover crop management (CC) and fields without cover crop management (NoCC) using continuous monitoring data from 40 agricultural fields located throughout northcentral Ohio, United States (US). We found that average monthly tile NO3−-N and TN loads from CC fields were ~50% less than NoCC fields, while average monthly tile discharge, DRP, and TP loads did not differ between CC and NoCC fields. Cover crops also did not significantly influence average monthly surface metrics. Cover crops reduced monthly totals of tile NO3−-N and TN loads by ~1.0–2.6 kg N ha−1 from January to June (winter and spring), coinciding with critical periods of nutrient loss from agroecosystems in the midwestern US, but increased monthly totals of tile DRP (by 0.4–12.1 g DRP ha−1) and TP (by 1.2–31.6 g TP ha−1) loads during some months. We found similar patterns at the annual time scale whereby CC fields had lesser cumulative annual totals of tile NO3−-N and TN but greater cumulative annual totals of tile DRP and TP. These results show that the influence of cover crops on N loads, but not P, were consistent across temporal scales of examination, demonstrating that cover crops effectively increased N demand and mitigated N losses from agricultural fields. The variable influence of cover crops on P loads underscores the need for greater understanding of the factors and mechanisms that control P loss in systems that include cover crop management. Furthermore, these findings stress the importance of identifying and selecting conservation management practices tailored to the natural resource concern.

Perennial cover crop biomass contributes to regulating soil P availability more than rhizosphere P-mobilizing capacity in rubber-based agroforestry systems

Cover crops used in agroforestry systems (AFS) are generally perceived to improve soil quality, but mechanisms underlying phosphorus (P) cycling in complex rhizosphere system are less clear, because the impacts of incorporated crops are often determined by inclusion time, residue management and species. We quantified 7-year cumulative effects of perennial legume cover crop–Flemingia macrophylla on rhizosphere P cycling and availability during the dry and wet seasons in young and mature rubber-based AFS (i.e., YAFS and MAFS) in tropical China by analyzing cover crop biomass and P content, as well as net rhizosphere changes in P-mobilizing capacity (pH, organic acids and phosphatase activity) and P fractions. Compared to their monoculture counterparts, YAFS enhanced plant biomass and P stock in both seasons, whereas MAFS exhibited an opposite trend, except for increased biomass and P stock of floor litter in the dry season. Moreover, YAFS had a greater effect on net rhizosphere properties by reducing pH and increasing organic acids concentrations and acid phosphatase activity, but MAFS hardly alter them. However, these changes had little effect on net rhizosphere P fractions in both seasons, except the contribution of calcium–P to increasing P availability to a certain extent. Net rhizosphere organic P and microbial biomass P in YAFS were enhanced in both seasons by abundant residue returns from cover crop. Net rhizosphere available P surplus occurred in YAFS in the dry season and maintained balance in the wet season, but it almost reached a deficit in MAFS in both seasons. These results suggest that rhizosphere P cycling was more improved by cover crop in YAFS than MAFS, and biomass of cover crop residue contributed to regulating rhizosphere P cycling and availability more than rhizosphere P-mobilizing capacity. Our study highlights the importance of residue management of permanent cover crops on rhizosphere P cycling and availability in AFS with different ages.

Winter cover crop management in the production of organic flue‐cured tobacco

AbstractLegume cover crops are not traditionally used in tobacco (Nicotiana tabacum L.) production due to concerns related to unpredictability of N supply and extended mineralization affecting quality of cured tobacco leaf. This study was conducted to determine if cover cropping with legumes could mitigate organic N fertilizer investment in tobacco without compromising yield, value, or quality. In 2018 and 2019, three winter cover crops: hairy vetch (Vicia villosa Roth) (HV); Austrian winter pea (Pisum sativum var. arvense L.) (AWP); and crimson clover (Trifolium incarnatum L.) (CC), were compared to a no‐cover crop control with typical organic N management in Rocky Mount and Kinston, NC. This study found no significant negative effects (α = .05) from legume cover cropping on yield or value of tobacco. In addition, AWP and HV increased yields between 13 and 37% compared to the no‐cover control. Value (US$ ha−1) did not differ from the control in 2018 or 2019 at any location, except at Kinston, where HV increased value 44% in 2019. In‐season soil samples suggest that HV provided N to tobacco up to flowering, however this did not negatively impact quality, yield, or value. Our research did not support grower concerns of prolonged N availability and found evidence that legume cover crops may allow for partial reduction in applied N without compromising the value of the product.

Soil Productivity Degradation in a Long-Term Eroded Olive Orchard under Semiarid Mediterranean Conditions

Olive groves are one of the most important agro-systems in the Mediterranean basin, and the Andalusia region produces the highest quantity of olive oil in Europe. The aim of this work was to evaluate the long-term (15 years) influence of two management practices in olive orchards—conventional tillage (CT) and no tillage with bare soil and herbicide application (NT + H)—on soil physical properties, infiltration capacity, erosion rates, and soil productivity. In addition, the short-term (2 years) influence of no tillage with cover crop management (NT-CC) on these parameters was also assessed. In the study area, CT and NT + H management practices showed unsustainable erosion values, 9.82 and 13.88 Mg ha−1 year−1, respectively, while NT-CC inclusion decreased the erosion rates (2.06 Mg ha−1 year−1). The implementation of NT-CC not only reduced erosion rates but also caused a change in the trend of soil productivity loss observed under CT and NT + H. In this sense, NT-CC showed a positive influence on soil quality. However, tillage removal led to a significant reduction in the infiltration capacity of soils under NT + H and NT-CC, which will be a serious handicap for water storage in an environment with continuous processes of water deficit.

Spring-planted cover crops for weed control in soybean

AbstractReplacing tillage with cover crops (CC) for weed management in corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] systems with mechanical weed control has many soil health benefits but in the western Corn Belt, CC establishment after harvest is hampered by cold temperatures, limited labor and few compatible CC species. Spring-planted CC may be an alternative, but information is lacking on suitable CC species. Our objective was to evaluate four spring-planted CC with respect to biomass production and weed suppression, concurrent with CC growth and post-termination. Cover crop species tested were oat (Avena sativa L.), barley (Hordeum vulgare L.), brown mustard [Brassica juncea (L.) Czern.] and yellow mustard (Brassica hirta Moench). They were compared to no-CC treatments that were either tilled pre- and post-planting of soybean (no-CC tilled) or not tilled at all (no-CC weedy). CC were planted in late March to early April, terminated 52–59 days later using an undercutter, and soybean was planted within a week. The experiment had a randomized complete block design with four replications and was repeated for 3 years. Mustards and small grains produced similar amounts of biomass (1.54 Mg ha−1) but mustard biomass production was more consistent (0.85–2.72 Mg ha−1) than that of the small grains (0.35–3.81 Mg ha−1). Relative to the no-CC weedy treatment, mustards suppressed concurrent weed biomass in two out of 3 years, by 31–97%, and small grains suppressed concurrent weed biomass in only 1 year, by 98%.Six weeks after soybean planting, small grains suppressed weed biomass in one out of 3 years, by 79% relative to the no-CC weedy treatment, but mustards did not provide significant weed suppression. The no-CC tilled treatment suppressed weeds each year relative to the no-CC weedy treatment, on average 87%. The ineffective weed control by CC reduced soybean biomass by about 50% six weeks after planting. While spring-planted CC have the potential for pre-plant weed control, they do not provide adequate early season weed suppression for soybean.

No-till technology has limited potential to store carbon: How can we enhance such potential?

No-till is a top soil conservation practice, but if it will be used as a C sequestration strategy, it needs enhancement. Companion practices including N fertilization and irrigation do not often result in net C sequestration or some are unavailable (i.e., biochar) for a large-scale application. Adoption of aggressive or transformative no-till companion practices that genuinely remove CO2 from the atmosphere through photosynthesis and sequester it in the soil as C should be considered. Enhancing both cover crops and crop rotation complexity can be an aggressive biological strategy to boost no-till performance; yet this has not been much discussed. Enhancing cover crops by increasing both the cropland area under no-till cover crops and cover crop biomass production through biomass yield maximization strategies can store more C in the soil than current no-till cover crop management practices. Additionally, inserting multi-year perennial or forages including grasses and legumes into existing no-till row crop rotations could store an additional amount of C. These no-till enhancement practices may not only increase C sequestration in the soil but also boost the overall resilience and ecosystem services from agricultural lands. Their potential can be particularly greater in low C (below C saturation) than high C (at or near C saturation) no-till soils.

Towards integrated cover crop management: N, P and S release from aboveground and belowground residues

Ecological intensification is crucial for arable organic farmers, in order to partly close the yield gap to conventional yields. One strategy for this is improved management of cover crops, to increase availability of both nitrogen (N), phosphorus (P) and sulfur (S) for the subsequent main crop. However, the potential of cover crops to take up and release nutrients has primarily been determined for aboveground biomass and mostly for N. There have been fewer studies on belowground biomass, and these have focused on recoverable roots. Thus, unrecoverable residues from rhizodeposits and nodules, have been overlooked. The aim of this incubation study was therefore to assess the release of N, P and S from aboveground residues and from intact soil with belowground residues of different cover crop species at low temperature. Shoots and intact soil with roots from seven different cover crops were incubated for 80 days at a temperature of 5 °C.A comparison of the cover crop species revealed a wide variation in nutrient uptake, chemical composition and release of N, P and S, that also varied between shoot and intact soil with roots. Release of N from shoots showed a marked non-stoichiometric behavior, in contrast to the release of P and S, that correlated well with C:P and C:S ratios. N release (from Vicia villosa) and especially P mobilization (from legumes) in intact soil was much greater than the amounts determined in recoverable roots. This shows that unrecoverable pools such as rhizodeposits and fine roots contributed to nutrient release. Garden sorrel (Rumex acetosa) is a promising cover crop regarding uptake and mobilization of P, but also as a multifunctional cover crop for supplying N, K, S and Mg. Hairy vetch (Vicia villosa) is a promising cover crop for N, oilseed radish (Raphanus sativus) for S, P and K, and white lupin (Lupinus albus) for N, P and Mn supply.Based on our results, we propose the use of mixtures of cover crops with different N, P and S uptake and release having the potential to supply a more complete suite of nutrients to the subsequent crop.

Organic Farming and Cover-Crop Management Reduce Pest Predation in Austrian Vineyards.

Simple SummaryGlobal declines in arthropods necessitate a rethinking of current agricultural practices. Organic farming, complex landscapes with high proportions of seminatural habitats and local vineyard management practices such as implementation of flower-rich cover-crop mixtures may be a promising approach to enhance arthropod biodiversity and, thus, natural pest control in viticulture. We examined effects of organic farming, different types of vineyard inter-row vegetation, and landscape composition on natural pest control of a major grapevine pest, the grape berry moth Lobesia botrana, and identified its dominant natural enemies. Surprisingly, natural pest control was reduced by sown cover-crops and organic farming. Interestingly, bush crickets were one of the most dominant natural enemies in the Austrian study region. Negative effects of organic farming in our study are most likely related to high fungicide inputs. Thus, a promising approach to reduce fungicide input and, therefore, promote a more sustainable viticulture may be the implementation of fungus-resistant grape varieties.Habitat simplification and intensive use of pesticides are main drivers of global arthropod declines and are, thus, decreasing natural pest control. Organic farming, complex landscapes, and local vineyard management practices such as implementation of flower-rich cover-crop mixtures may be a promising approach to enhance predator abundance and, therefore, natural pest control. We examined the effect of organic versus integrated management, cover-crop diversity in the vineyard inter-rows, and landscape composition on the natural pest control of Lobesia botrana eggs and pupae. Predation of L. botrana pupae was reduced by organic farming and species-poor cover-crops by about 10%. Predation rates of L. botrana eggs did not differ significantly in any of the studied management options. Dominant predators were earwigs (Forficulidae), bush crickets (Tettigoniidae), and ants (Formicidae). Negative effects of organic viticulture are most likely related to the negative nontarget effects on arthropods related to the frequent sulfur and copper applications in combination with the avoidance of strongly damaging insecticides by integrated winegrowers. While a 10% difference in predation rates on a single pest stage is unlikely to have strong practical implications, our results show that the assumed effectiveness of environmentally friendly agriculture needs to be evaluated for specific crops and regions.

Management of cover crops in temperate climates influences soil organic carbon stocks: a meta-analysis.

Increasing the quantity and quality of plant biomass production in space and time can improve the capacity of agroecosystems to capture and store atmospheric carbon (C) in the soil. Cover cropping is a key practice to increase system net primary productivity (NPP) and increase the quantity of high-quality plant residues available for integration into soil organic matter (SOM). Cover crop management and local environmental conditions, however, influence the magnitude of soil C stock change. Here, we used a comprehensive meta-analysis approach to quantify the effect of cover crops on soil C stocks from the 0-30cm soil depth in temperate climates and to identify key management and ecological factors that impact variation in this response. A total of 40 publications with 181 observations were included in the meta-analysis representing six countries across three different continents. Overall, cover crops had a strong positive effect on soil C stocks (P<0.0001) leading to a 12% increase, averaging 1.11Mg C/ha more soil C relative to a no cover crop control. The strongest predictors of SOC response to cover cropping were planting and termination date (i.e., growing window), annual cover crop biomass production, and soil clay content. Cover crops planted as continuous cover or autumn planted and terminated led to 20-30% greater total soil C stocks relative to other cover crop growing windows. Likewise, high annual cover crop biomass production (>7Mg·ha-1 ·yr-1 ) resulted in 30% higher total soil C stocks than lower levels of biomass production. Managing for greater NPP by improving synchronization in cover crop growing windows and climate will enhance the capacity of this practice to drawdown carbon dioxide (CO2 ) from the atmosphere across agroecosystems. The integration of growing window (potentially as a proxy for biomass growth), climate, and soil factors in decision-support tools are relevant for improving the quantification of soil C stock change under cover crops, particularly with the expansion of terrestrial soil C markets.

Impact of Grass Cover Management with Herbicides on Biodiversity, Soil Cover and Humidity in Olive Groves in the Southern Iberian

In the present work, we studied the effect of herbicide use on extensive olive grove cultivation. To carry out this study, we analysed the effect that herbicide use had on biodiversity, vegetation cover and soil water content. For this purpose, 96 vegetation and soil sampling points were first taken, then georeferenced, and for each sampling point, several bioclimatic variables were interpolated. We concluded that the management of cover crops with herbicides over a long period of time resulted in a decrease in biodiversity, and the dominance of some species that were more resistant to herbicides was increased. Another finding was that the vegetation cover was reduced in the resampling in cases with herbicide management and that the location within the cropland (under the tree canopy, road, boundary or pasture) also has an influence. Finally, the study of soil moisture shows that soil water content was lower in the case of management with herbicides than in the case of management without herbicides. This loss of soil moisture was more accentuated and faster in areas with less vegetation cover. This work highlights the need to change the management models for tree crops in order to preserve biodiversity, soil quality and optimise water resources in a context of accelerated climate change in one of the regions most severely affected by global warming, the Mediterranean belt.