Cover Crop Species Research Articles

Evaluating high‐resolution optical and thermal reflectance of maize interseeded with cover crops across spatial scales using remotely sensed imagery

AbstractWe evaluated the optical and thermal reflectance of maize (Zea mays L.) interseeded with cover crops using remotely sensed canopy temperature and multispectral imagery. In 2017 and 2018 annual ryegrass (Lolium multiflorum Lam.), crimson clover (Trifolium incarnatum L.), oilseed radish (Raphanus sativus L.), and a mixture of annual ryegrass and crimson clover were interseeded in maize at V3 and V6 at three different cover crop seeding rates in small research plots at two experimental farm sites within the network of Michigan State University. The same cover crop species were interseeded in maize at V3 and V6 at a single seeding rate in on‐farm replicated strip trials and also a full‐scale field trial at five locations in Michigan. Canopy temperature and multispectral reflectance were remotely measured 10–12 times throughout each season at all sites using fixed wing aircraft at 1‐m spatial resolution. Optical and thermal reflectance were also measured remotely using an unmanned aerial vehicle (UAV) with 2‐cm spatial resolution three times during the growing season at the small plot sites. Normalized difference vegetation index (NDVI) and normalized difference red‐edge (NDRE) were calculated for each of the experimental sites. No significant differences were detected between the interseeded treatments and control with regards to the optical and thermal reflectance and maize grain yield. Variability at field scale was due to inherent differences and not caused by the interseeding treatments.

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.

Autonomous Mowing and Complete Floor Cover for Weed Control in Vineyards

Enhancing vineyards sustainability and reducing herbicides usage is a crucial theme, thus alternative weed management methods are starting to be studied. Cover crops have been shown to provide for several environmental services such as performing an efficient weed control and promoting biodiversity, thus improving the sustainability of the overall management system. However, the use of cover crops is usually confined to the interrow area in order to avoid competition with vines. Under-trellis weed management in vineyards is an important challenge, conventionally fulfilled by cultivation or repeated herbicides applications. Autonomous mowers are small autonomous machines that have shown a great efficiency when employed in agricultural contexts. Due to their reduced size, they can easily prevent the excessive vertical growth of weeds both in the interrows and under trellis without the use of chemical applications. The aim of this trial was to evaluate if the combination of cover crop species and autonomous mowers management could improve vineyard sustainability. Vineyard floor cover that was managed with an autonomous mower had a shorter canopy height and a lower weed dry biomass compared to the conventionally managed vineyard floor cover. Vineyard floor management providing cover crops and autonomous mowing had a significantly lower weed cover percentage compared to conventional floor management, especially under-trellis. The results of this trial suggest that the combination of cover crops and autonomous mowers may be a sustainable and reliable technique to include in vineyards floor management.

Intercropping and rotation with leguminous plants in organic vegetables: crop performance, soil properties and sustainability assessment

ABSTRACT This research was carried out in an organic crop sequence of cauliflowers (Brassica oleracea L.) and tomatoes (Solanum lycopersicum L.) intercropped with different cover crop species (burr medic (Medicago polymorpha L) and crimson clover (Trifolium incarnatum L.)) grown as living mulches and cultivated on a ridge system on a site characterised by extreme weather events (floods) in the Mediterranean environment. The objectives of the research were to: (i) investigate the impact of the combination of agro-ecological techniques (cover crops and organic fertilisation) on cash crops yield, biomass production and selected physical properties of the soil; (ii) evaluate the sustainability of the systems by using both energy inputs/outputs analysis and assessment of greenhouse gas emissions (GHG). Six treatment combinations were compared: intercropping with burr medic throughout the crop rotation, with and without organic fertilisers; growing crimson clover as a living mulch in the winter crop within the crop rotation, with and without organic fertilisers; cropping system without cover crops, with and without organic fertilisers. The findings highlighted that the introduction of cover crops in the rotation should be recommended since it resulted in higher crop production levels without negative impacts on soil physical properties, as well as in the best energy use efficiency and carbon efficiency in the system. The results of the soil physical quality assessment indicated that the agro-ecological practices had no significant effects on the soil properties. Therefore, in the Mediterranean conditions, the proposed agro-ecological approaches can be crucial to achieving sustainable organic agro-ecosystems.

Soil organic C affected by dry‐season management of no‐till soybean crop rotations in the tropics

Cover crop species selection for soybean (Glycine max) production under no-tillage (NT) management may affect soil organic C sequestration by altering the quantity and quality of C inputs, thereby affecting cropping system sustainability. If so, the underlying mechanisms for such regulation are still unclear. We assessed changes in soil C and N fractions at 0-0.1 m depth and soil C stock at 0-0.6 m depth during the last three years of dry-season cover cropping in a soybean production system managed with NT for 9 years on a Rhodic Hapludox in Sao Paulo, Brazil. Dry-season management treatments were repeated yearly in a split-plot scheme. Main plots during the fall-winter were (1) ruzigrass (Urochloa ruziziensis), (2) grain sorghum (Sorghum bicolor), and (3) the intercropping of ruzigrass and sorghum. Subplots during spring prior to planting soybean were (a) pearl millet (Pennisetum glaucum), (b) sunn hemp (Crotalaria juncea), and (c) forage sorghum (Sorghum bicolor). Soil C and N fractions were affected according to crop residue characteristics of the rotations. Higher soil C stocks in 2012 and 2015 (7 % an average) were observed at 0.2–0.4 m depth by ruzigrass compared to sorghum. High crop residue input with ruzigrass in the fall-winter sequestered 0.61 Mg C ha− 1 yr− 1 at 0-0.1 m soil depth compared with lower C sequestration using grain sorghum (0.29 Mg C ha− 1 yr− 1). The quantity and quality of crop residues impact its retention on soil surface controlling the dynamics of soil C and N fractions and can be considered relevant for soil C sequestration. These aspects could contribute to the mitigation of atmospheric CO2 in crop production systems.

Ecosystem Services and Cash Crop Tradeoffs of Summer Cover Crops in Northern Region Organic Vegetable Rotations

Intensive production practices characterizing vegetable farming contribute to high productivity, but often at the expense of supporting and regulating ecosystem services. Diversification with cover crops may support increased resilience through soil organic matter (SOM) contributions and physical soil protection. Vegetable farming often includes spring and fall production, limiting establishment and productive potential of over-wintered cover crops that are more widely used in the USA. In northern climate vegetable systems, warm-season cover crops planted during short summer fallows could be a tool to build resilience via ecosystem service enhancement. This project evaluated summer cover crops in the northern USA (MN and WI) for biomass accumulation, weed suppression, and contribution to fall cash crop yield. Our study included four site years, during which we investigated the effects of four cover crop species treatments, grown for 30 (short duration, SD) or 50 days (long duration, LD) alongside bare fertilized and unfertilized control treatments: buckwheat (Fagopyrum esculentum) and sunn hemp (Crotalaria juncea) monocultures, and biculture of chickling vetch (Lathyrus sativus) or cowpea (Vigna unguiculata) with sorghum-sudangrass (sudex) (Sorghum bicolor x S. bicolor var. Sudanese). To quantify cover crop quantity, quality, and weed suppression capacity, we measured cover crop and weed biomass, and biomass C:N. To quantify effects on cash crops, we measured fall broccoli yield and biomass. Mean total biomass (cover crop + weeds) by site year ranged from 1,890 kg ha−1 in MN Y1 to 5,793 kg ha−1 in WI Y2 and varied among species in Y1 for both the SD and LD treatments. Most cover crops did not outcompete weeds, but treatments with less weeds produced more overall biomass. Data from Y1 show that cover crops were unable to replace fertilizer for fall broccoli yield, and led to reduced fall crop yield. Broccoli in Y2 did not reach maturity due to fall freeze. Summer cover crops, because of their biomass accumulation potential, may be used by farmers in northern climates to fit into cropping system niches that have historically been left as bare soil, but care with timing is necessary to optimize weed suppression and mitigate tradeoffs for cash crop production.

Color, odor, and species preferences of Copidosoma bakeri to prospective cover crops to enhance control of cutworms

AbstractCutworms (Lepidoptera: Noctuidae) are economically important pests of multiple field crops, but are difficult to control with insecticides. Biological control with native parasitoids may offer a sustainable alternative for pest management. Cover crops improve the availability of resources required by parasitoids to increase their effectiveness as biocontrol agents. Copidosoma spp. (Hymenoptera: Encyrtidae) have the potential to control several species of cutworms in the Canadian Prairies. However, their foraging preferences for non‐host food items are unknown. In this study, we tested flower color and odor preferences of Copidosoma bakeri (Howard) across nine potential cover crop species and investigated how these resources affect survival and longevity of the female wasps. Results indicated that the wasps were most attracted to plants with yellow flowers in the family Brassicaceae (i.e., camelina, mustard, and canola). In multiple‐choice tests, the wasps preferred camelina over all other flower species, and showed an intermediate preference for mustard and canola. In dual‐choice tests with color paper, the wasps preferred yellow over white, and the light yellow of camelina over the bright yellow of canola and mustard, whereas they showed a preference for the odors of mustard and canola. Life expectancy was increased when the wasps were provided floral resources compared to the absence of a food source. Later planting dates and mixed‐species plantings of cover crops resulted in flowering times that better coincided with native wasp emergence. Camelina is known to suppress weeds and may be used as a habitat management tool for enhancing parasitism of cutworms by C. bakeri in the Canadian Prairies. However, further testing is needed to achieve late flowering well into August and early September and to ensure planting additional Brassica spp. does not attract more late‐season pests to cash crops such as canola.

Developing functional relationships between temperature and cover crop species vegetative growth and development

AbstractCover crops planted in the offseason are subjected to uncontrollable weather variables that limit agro‐ecological services through modifications in growth and development. The growth of five cover crop species was investigated in response to an array of day/night temperatures, 17/9, 22/14, 27/19, 32/24, and 37/29 °C. Shoot and root parameters were measured 33 d after planting. Quadratic functions best described most of the root and shoot dynamics in response to increasing temperatures except for a linear response of plant height in crimson clover (Trifolium incarnatum) and mustard (Brassica juncea). Temperature minimum (Tmin), maximum (Tmax), and optimum (Topt) for shoot traits varied from 9.8 to 10.6, 37.5 to 43.2, and 23.9 to 26.5 °C, respectively. The Tmin for root traits varied significantly, ranging from 8.5 to 10.8 °C. Topt and Tmax ranged from 22 to 25.7 and 35.2 to 40.6 °C, respectively. On average, the Topt for root traits was significantly lower than shoot traits in four of five species. Regardless of temperatures, cover crop species recorded higher biomass partitioning to shoot (62%) than to root, with a maximum proportion of biomass partitioned to shoot in crimson clover and Mighty Mustard Pacific Gold (80%) than other species (64–70%). The results of this study will help growers choose mixes of cover crops with the same temperature range to plant in the same climatic conditions during fallow periods. The cardinal temperatures and functional algorithms for growth and developmental traits could be used to develop models for cover crops under different temperature conditions.

Nitrogen dynamics in grain cropping systems integrating multiple ecologically based management strategies

AbstractNitrogen (N) management is a critical agronomic challenge, as N losses are a source of pollution affecting both waterways and air quality and a potential economic loss for farmers. One approach to N conservation is through ecologically based agricultural systems that reduce tillage and incorporate cover crops. However, these systems exhibit considerable complexity resulting in potential agronomic trade‐offs. To address these concerns, four crop management systems were implemented within an organically managed corn–soy–winter grain crop rotation. These systems varied in tillage frequency and intensity, cover crop species selection, cover crop termination and establishment methods, fertilizer management, and cash crop season length. We used field measurements to investigate the impact of each system on N pools and to reveal the strengths and weaknesses of each system in addressing N provisioning services, with a focus on the supply and retention of N before and after the corn phase of the rotation. All systems had greater estimated N inputs (via manure and N‐fixation) than outputs (via crop harvest) at the end of the three‐year rotation, demonstrating the importance of prioritizing N retention in cover crops. Interactions among system components were important drivers of temporal N dynamics; cover crop species traits and timing of manure application contributed to differences in total aboveground plant biomass N among systems. For example, one cropping system which included a no‐till corn planting into a rolled cover crop mulch had soil inorganic N availability that was asynchronous with the N needs of the corn crop even though it received the same amount of N inputs as the other systems. In general, neither interseeding cover crop mixtures nor reducing tillage resulted in marked N benefits at the system level; we did not observe improved N retention from either practice in these systems, and there was no increase in N uptake by corn. What did clearly emerge from this experiment is the importance of managing for synchrony between soil inorganic N availability and cash crop N demand as influenced by the N retention capacity of cover crops and the timing of N mineralization due to tillage.

Nutrient stoichiometry of a plant-microbe-soil system in response to cover crop species and soil type

AimsThe theory of ecological stoichiometry mostly builds on studies of natural terrestrial ecosystems, whereas only limited stoichiometry information is available in response to agronomic practices.MethodsWe designed a greenhouse experiment in order to disentangle the specific role of cover crop identity and soil characteristic in affecting nutrient stoichiometry of a plant-microbe-soil system.ResultsNutrient ratios of cover crop biomass were species-specific and the growth rate explained, for most species considered, the stoichiometric differences in response to soil type. In contrast, the nutrient stoichiometry of soil microbes was more homeostatic and did not respond to either cover crop identity or soil type. Compared to bare soil, the presence of cover crop enhanced microbial phosphorus immobilization in the clay-rich soil, whereas it promoted microbial carbon biomass and microbial nitrogen immobilization in the sandy-rich soil. A greater microbial cumulative respiration in clay soils, where a higher microbial biomass C at the beginning of the incubation was observed, suggested a major role of soil type, compared to cover crop identity, in affecting microbial metabolism.ConclusionsBy understanding the stoichiometric constraints in the plant-microbe-soil system, our findings can help to implement agro-ecological practices by selecting appropriate cover crop species in relation to soil type in order, for example, to avoid nutrient limitation due to microbial nutrient immobilization.

Impact of Ambient and Elevated [CO2] in Low Light Levels on Growth, Physiology and Nutrient Uptake of Tropical Perennial Legume Cover Crops.

At early stages of establishment of tropical plantation crops, inclusion of legume cover crops could reduce soil degradation due to erosion and nutrient leaching. As understory plants these cover crops receive limited irradiance and can be subjected to elevated CO2 at ground level. A glasshouse experiment was undertaken to assess the effects of ambient (450 µmol mol−1) and elevated (700 µmol mol−1) levels of [CO2] on growth, physiological changes and nutrient uptake of six perennial legume cover crops (Perennial Peanut, Ea-Ea, Mucuna, Pigeon pea, Lab lab, Cowpea) under low levels of photosynthetic photon flux density (PPFD; 100, 200, and 400 µmol m−2 s−1). Overall, total and root dry biomass, total root length, specific leaf area, and relative growth rates were significantly influenced by levels of [CO2] and PPFD and cover crop species. With few exceptions, all the cover crops showed significant effects of [CO2], PPFD, and species on net photosynthesis (PN) and its components, such as stomatal conductance (gs) internal CO2 conc. (Ci), and transpiration (E). Increasing [CO2], from 450 to 700 μmol mol−1 and increasing PPFD from 100 to 400 μmol ּm−2 ּs−1 increased PN. Overall, the levels of [CO2], PPFD and species significantly affected total water use efficiency (WUETOTAL), instantaneous water use efficiency (WUEINST) and intrinsic water use efficiency (WUEINTR). With some exceptions, increasing levels of [CO2] and PPFD increased all the WUE parameters. Interspecific differences were observed with respect to macro-micro nutrient uptake and use efficiency. With a few exceptions, increasing levels of [CO2] from 450 to 700 μmol mol−1 and PPFD from 100 to 400 μmol m−2 s−1 increased nutrient use efficiency (NUE) of all nutrients by cover crop species.

Cover Crop and Pruning Residue Management to Reduce Nitrogen Mineral Fertilization in Mediterranean Vineyards

This paper aimed to study the effect of temporary cover crop and vine pruning residue burial as alternative practices to conventional tillage on soil nitrate (NO3-N) availability and grapevine performance in the short term. The trial was carried out in a rain-fed vineyard (Vitis vinifera L., cv Grecanico dorato/140 Ruggeri) located in a traditional Mediterranean viticultural area (37°32′48′′ N; 13°00′15′′ E) in Sicily (Italy). Conventional tillage (CT) soil management was compared with winter cover crop (CC), conventional tillage plus buried pruning residue (CT + PR), and winter cover crop plus buried pruning residue (CC + PR) management treatments. Two fertilizer treatments (92 kg ha−1 of N as urea and 0 kg ha−1) were applied to the four soil management treatments. Vicia faba L. was the selected leguminous cover crop species, which was seeded in autumn and buried in spring at the same time as vine pruning residues. The soil NO3-N content was monitored, and vine vegetative growth, yield, and must quality were assessed over two seasons. Results showed that NO3-N availability strongly differed between fertilized (F) and unfertilized (UF) plots and years and among treatments. A positive effect of winter leguminous CC + PR on the Grecanico dorato grapevine performance was observed. In the UF vineyard, grape fertility, yield, Ravaz index, and total soluble solids were significantly higher in CC + PR vines than in other treatments, thus showing the reliability of reducing N mineral fertilization and related risks of excess nitrate in groundwater. The possibility of increasing the overall sustainability of rain-fed vineyards in a semiarid agro-ecosystem, without negative effects on grape and must quality, is also demonstrated.

Does Cover Crop Management Affect Arthropods in the Subsequent Corn and Soybean Crops in the United States? A Systematic Review

Abstract Cover crops (CC) support populations of pest and beneficial arthropods. The status of these arthropods in the subsequent cash crop depends on several factors such as CC species, management, biomass production, and weather conditions. A systematic review was performed to identify how CC management influences pest and beneficial arthropods and to identify knowledge gaps for the future research efforts. Eight studies included in this review indicated that CC increase beneficial arthropods or some beneficial arthropods compared with the CC managed fields. A minority of the studies indicated an increase in pest presence when using CC. Cover crop species, termination time and methods, and CC management had variable responses on arthropod activity-density. The variable responses, differences on study designs, and complexity of CC management influence arthropod activity in a CC-corn [Zea mays L. (Poaceae)]/soybean [Glycine max L. (Fabaceae)] system, limiting our ability to draw a broad and effective conclusion about the CC management impact on arthropods. Local research studies are needed to identify the impact of CC biomass quality and quantity, CC biomass thresholds for pest and beneficial arthropods, and cash crop yield impact of CC management-arthropod-related studies. Studies using the standard farming practices of each U.S. region and using standard measurements are needed to guide farmers that use cover crops. This systematic review aims to provide a better understanding of how the complexity of management in cover crop-corn/soybean management affects arthropod activity-density and to identify potential gaps in research and address future research needs.

Cover crops reduce soil resistance to penetration by preserving soil surface water content

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.

Absorption of nutrients and chemical reconditioning of red latosol by cover plants cultivated in Amazon environment

Maintaining the balance of the system using cover crops is a promising alternative for the Amazon region. In this context, the present study aimed to evaluate the absorption of nutrients by cover crops and the reconditioning of soil chemical attributes after management with different cover crops. The experiment was conducted in the experimental area of the Federal Institute of Education, Science and Technology of Rondonia, Colorado do Oeste Campus, in the municipality of Colorado do Oeste, RO, Brazil. The experimental design used was completely randomized, arranged in a 7x4 factorial scheme, consisting of seven species of cover crops (Crotalaria spectabilis, Crotalaria breviflora, Crotalaria ochroleuca, Mucuna aterrima, Mucuna pruriens, Dolichos lablab and Canavalia ensiformis) and four sampling depths (0-10 cm, 10-20 cm, 20-30 cm and 30-40 cm), with four replicates. The results concluded that the cultivation of Crotalaria spectabilis, Crotalaria ochroleuca and Crotalaria breviflora provided higher dry matter yield. The species Dolichos lablab stood out in the accumulation of nitrogen, phosphorus, calcium and sulfur in the leaves at full flowering. The contents of organic matter, total carbon, C/N ratio, N-total, P, K, Ca2+ and Mg2+ of the soil were higher at the depth of 0-10 cm with a decrease in subsurface layers. The species Dolichos lablab and Mucuna pruriens are efficient in terms of supplying organic matter, organic carbon, C/N ratio, N-total, phosphorus, calcium and Ca/Mg ratio of the soil, promoting a direct impact on the fertility of its surface layers up to 10 cm deep. Cultivation of Crotalaria breviflora and Crotalaria spectabilis caused variation in soil exchangeable bases, being directly correlated with the values of pH, SB and CEC

The potential of nutrient cycling in cover plants in response to phosphate fertilization

Residues of crops and cover crops contain considerable amounts of phosphorus (P) in their tissues, which through their mineralization can meet much of the requirement of crops. In this context, the present study aimed to evaluate the biomass production, P absorption and use of different cover crops subjected to phosphate fertilization, and its effects on the absorption and use of nitrogen (N), phosphorus (P) and potassium (K). The experiment was conducted in a protected environment from August to December 2019. The experimental design was completely randomized, arranged in a 7 x 3 scheme, consisting of the planting of seven species of cover crops (Crotalaria spectabilis, Crotalaria breviflora, Crotalaria ochroleuca, Mucuna aterrima, Mucuna pruriens, Dolichos lablab and Canavalia ensiformis), three P rates (0, 80 and 160 kg ha-1 of P2O5) and four replicates. At the time of full flowering, the cover species were cut and divided into root and shoot for subsequent determination of dry mass production, nutrient content and absorption efficiency and nutrient utilization. The results showed that Canavalia ensiformis promoted higher yield of shoot fresh and dry mass, P content in the shoots and higher N and P absorption efficiency. N and P contents in Dolichos lablab roots were higher at the highest P rates (160 kg ha-1 of P), without close relationship with the supply of shoot dry mass. The P dose of 160 kg ha-1 had an increasing and significant effect on the production of shoot fresh mass and dry mass, N, P and K contents in the shoots, N, P and K contents in the roots and efficiency of N, P and K use by the different cover crops. The P rates of 80 kg ha-1 increased the N, P and K contents in the shoots of Crotalaria ochroleuca, Crotalaria breviflora and Crotalaria spectabilis; and at higher P rates, there was a reduction in nutrient accumulation. The species Mucuna pruriens and Mucuna aterrima were efficient in the use of N, P and K at P rates of 160 kg ha-1.

Impact of Cover Crop Species on Soil Physical Properties, Cotton Yield, and Profitability

Poor soil health purportedly limits crop yield and on-farm profitability in environments with a history of intensive tillage. Research was conducted to determine if cover cropping improves basic soil physical properties, crop productivity, and economic parameters in conventionally tilled soils. The effects of irrigation and cover crop species on bulk density, water infiltration rate, cotton yield, and net returns were evaluated on a Dundee silty clay loam (Fine-silty, mixed, active, thermic type Typic Endoqualfs) near Tribbett, MS in 2017 and a Leeper silty clay loam (fine, smectitic, nonacid, thermic Vertic Epiaquepts) near Starkville, MS from 2017 through 2018. Relative to the fallow production system, cereal rye and crimson clover decreased bulk density 4.6% but had no effect on water infiltration rate. Pooled over year and location, cover crop had no effect on lint yield in either irrigated or non-irrigated environments. However, transitioning from conventional to a cover crop system reduced net returns for cotton $50.22/ha to $307.87/ha on average. Our data indicate that while transitioning from a conventional to a fall cover crop production system, modest improvements in some soil physical properties due to cover crop establishment will not increase cotton productivity but will decrease net returns.

Soil pH, nitrogen, phosphatase and urease activities in response to cover crop species, termination stage and termination method

The best management options for cover cropping are largely unknown, including the growth patterns of cover crop (CC) species, optimum termination stages and termination methods. A greenhouse experiment was conducted to explore the following: (i) Effect of two termination stages (vegetative and flowering) on the chemical composition (N and C:N) of four CCs; (ii) Short-term impacts of living CCs and residues on soil pH, total N, urease and phosphatase activities at the two termination stages, and under two termination methods (slash and spray). Species tested as CCs were, vetch (Vicia dasycarpa L.), field pea (Pisum sativum L.), oats (Avena sativa L.), rye (Secale cereal L.) and a control (no CC). The experiment was set up in a randomized block design with three replications. Soil was sampled at kill and one year after CC kill. Delaying termination from vegetative till flowering stage decreased N in the tissue of P. sativum, A. sativa, V. dasycarpa and S. cereal by 59%, 65%, 44% and 56%, respectively, while their C:N ratios increased. Cover crop presence had no effect on soil pH. Living CCs had no significant effect on soil N concentration. The activities of urease and phosphatase were stimulated by all the living CC species. Unlike urease, all CC residues had a positive impact on phosphatase activity at one year. Only P. sativum and V. dasycarpa residues increased soil N concentration in the short-term. Compared to flowering, termination at vegetative stage improved soil N concentrations and phosphatase activity at both sampling times. Termination method had no effect on soil N, urease and phosphatase activity at one year. The significant interaction (P < 0.05) of sampling time, CC and termination stage effects on soil N concentration and phosphatase activity observed in this study indicates that these management approaches can optimize CC benefits and improve soil chemical and biological properties.

Effect of Rye and Mix Cover Crops on Soil Water and Cotton Yield in a Humid Environment

In recent years, the use of cover crops is becoming a popular technology among growers in many regions of the United States, which is expected to deliver various benefits such as improving soil health, increasing soil organic matter, controlling weeds, and helping conserve soil water and nutrients. Although expecting these benefits seems reasonable, it is challenging to know how much of these benefits to expect under specific situations. The potential effect of cover crops on soil water conservation is especially significant because of the documented impact of soil water on crop yield, especially for dryland cropping systems. Some researchers have found that planting a cover crop tended to increase soil water, while others have reported the opposite effect. Information on the impact of cover crops on soil water in cotton (Gossypium hirsutum L.) production systems in South Carolina is currently lacking. Therefore, the objective of this study was to quantify the effect of cover crops on soil water and cotton yield. A field experiment was conducted in South Carolina during winter, spring, and summer of 2015, with three cover crop treatments. The treatments included: 1) rye (Secale cereale L.), planted alone; 2) a mix of six cover crop species; and 3) a control treatment with no-cover. The cover crop was established in the winter, terminated in the spring, and cotton was grown during the summer. Soil water was measured at different depths using capacitance probes and a neutron probe. Our results showed no significant differences in soil water and cotton yield among the cover crop treatments. These results suggest that under the humid conditions of this study, any short-term effect of the cover crop on soil water was masked by timely rain.

Cover crop residue diversity enhances microbial activity and biomass with additive effects on microbial structure

Context Cover crops are used to improve soil fertility and environmental sustainability. Decomposition of cover crop residues can affect belowground microbial communities and activity, which is important for soil functions (e.g. nutrient cycling, organic matter decomposition). Aims We investiagated the effect of plant residues from a range of cover crop species on soil microbial activity, diversity and microbial community composition. Methods A mixture of four cover crop residues (buckwheat, clover, sunflower, radish) or an equal mass of the residues of each of the individual species were assessed for their effect on soil respiration and soil microbial community structure. Key results Cover crop residue incorporation significantly (P &lt; 0.001) increased soil respiration during 84 days incubation and this response caused a significant change in microbial community composition by increasing the proportion of fungi and Gram-positive bacteria at the cost of decreasing Gram-negative bacteria. The mixture of cover crop residues had a significantly (P &lt; 0.05) greater soil respiration rate, by 57.61 μg C g−1 h−1, than the average of the four individual residues, but did not have a significantly different soil microbial biomass or microbial community structure. Conclusions Greater diversity of organic resources increased the number biochemical niches, and activated dormant microbial communities to increase activity without affecting biomass or community composition. Greater respiration from similar microbial biomasses suggests that microbial activity might be more efficient following more diverse substrate input. Implications The positive impact of cover crop residues on soil microbial activity suggests that mixtures of cover crop residues may enhance soil functions beyond the sum of individual cover crop residues.