Cover Crop Practices Research Articles

EFFECT OF WHITE CLOVER (TRIFOLIUM REPENS 'HUIA') COVER CROP ON AGRONOMIC PROPERTIES AND SOIL BIOLOGY IN AN ORGANIC PEACH ORCHARD

In orchards, cover crops are interesting alternative strategies to tillage or chemical herbicides for managing weeds in the tree row. However, little is known about the effect of cover crops on agronomic properties and soil biology in organic orchards. To fill this gap, the effects of two weed managements, a White clover cover crop (CC) versus classical tillage practice (T) on the tree row, were assessed in an irrigated organic Peach orchard. White clover was sown in 2004, 2006 and 2009 in the tree row and ploughed in 2006 and 2008. Root density, earthworm density, water infiltration rate, nitrogen content and water availability were measured in the soil, in the tree row. In 2009, peach root density observed in the superficial layers was higher in CC treatment. Sampling dates and treatment have a significant effect on total earthworm density with higher abundance observed in CC. However, no difference was observed between CC and T anecic earthworm groups known to make large and vertical burrows. Infiltration rate measured with the simplified Beerkan method was higher in CC treatment. This could be explained by the thick superficial root mat which was associated to a significant higher epigeic earthworm density in CC. Whereas nitrogen supplies were twice lower in CC treatment since 2005, soil nitrogen availability was equivalent in both treatments. These results demonstrate the agronomic interest of nitrogen-fixing plants used as a cover crop in organic peach orchards.

Influence of Floor Management Technique on Grapevine Growth, Disease Pressure, and Juice and Wine Composition: A Review

Vineyard floor management has multiple goals that encompass improving weed management and soil conservation, reducing soil resource availability to control vine vigor, and influencing desirable aspects in wine quality. This review addresses the effects of cultivation, weed control, cover crops, and mulch on vine growth and balance, disease pressure, yield, and juice and wine quality in many growing regions (Australia, New Zealand, South Africa, Europe, and the western United States); offers recommendations for practical use; and highlights research needs. In the last decade, more literature has been published on mulching and cover cropping than on cultivation and herbicide use, suggesting stronger interest in cover cropping and mulching practices for vineyards. Cover crops have the potential to improve soil and vine health, can be adapted to many climates and soils, and may influence vine vigor by adjusting parameters such as the length of their growth period, coverage of the vineyard floor, and aggressiveness. Cover crops increased juice soluble solids, anthocyanins, and other phenolic components and decreased titratable acidity and pH. They were associated with red wines judged superior to those issued from non-cover-cropped vines. Use of organic mulches resulted in improved vine balance, soil water content, and friability, increased yields, and reduced pathogen and pest pressure. Plastic and fabric mulches remain impractical due to high installation cost. Application of newer techniques such as flame weeding or soil steaming is limited due to difficulty in targeting the appropriate stage of weed growth and limited susceptibility of some weed species to these techniques. Research needs include development of multiyear, multidisciplinary studies that use a mechanistic approach to link management practices to soil processes, grapevine responses, grape and wine composition, and sensory characteristics.

Use of N immobilization to tighten the N cycle in conventional agroecosystems

Soils in conventional agroecosystems are purposely held in a nitrogen (N)-saturated state to maximize crop yields. Planting winter annual cover crops when fields are usually fallow has been proposed to ameliorate N losses from soils. In this study we introduced winter annual cover crops into an N rate study with plots fertilized at 0, 34, 67, 101, 134, 168, and 202 kg N/ha in maize (Zea mays L.) to determine how winter annual cover crops affect yields, N2O and NO3- fluxes, and N pools. At the six-leaf stage and during flowering, incorporation of cover crop into soil resulted in a 30% reduction in maize biomass. Three weeks after fertilization, KCl-extractable soil mineral N was 75-87% lower in covercropped soils than in no-cover soils, indicating that N had been immobilized in the covercropped soils. At physiological maturity, there was no difference between cover and no-cover treatments in crop yield, which was maximized at 9 Mg/ha in 2006 and 7 Mg/ha in 2007. Where N rates exceed crop requirements, cover crop incorporation may reduce N exports as NO3- and N2O. Tighter N cycling in conventional agroecosystems could be fostered by matching N rates to the amount of N removed with grain and using N immobilization to retain N and support yields. If N immobilization is viewed as a means for efficient fertilizer N use rather than a process that decreases crop productivity, growers might be more willing to adopt cover-cropping practices.

Molecular Characterization of Fungal Communities in Non-Tilled, Cover-Cropped Upland Rice Field Soils

This study aimed to characterize soil fungal communities in upland rice fields managed with tillage/non-tillage and winter cover-cropping (hairy vetch and cereal rye) practices, using PCR-based molecular methods. The study plots were maintained as upland fields for 5 years and the soils sampled in the second and fifth years were analyzed using T-RFLP (terminal restriction fragment length polymorphism) profiling and clone libraries with the internal transcribed spacer (ITS) region and domain 1 (D1) of the fungal large-subunit (fLSU) rRNA (D1(fLSU)) as the target DNA sequence. From the 2nd-year-sample, 372 cloned sequences of fungal ITS-D1(fLSU) were obtained and clustered into 80 nonredundant fungal OTUs (operational taxonomic units) in 4 fungal phyla. The T-RFLP profiling was performed with the 2nd- and 5th-year-samples and the major T-RFs (terminal restriction fragments) were identified using a theoretical fragment analysis of the ITS-D1(fLSU) clones. These molecular analyses showed that the fungal community was influenced more strongly by the cover-cropping than tillage practices. Moreover, the non-tilled, cover-cropped soil was characterized by a predominance of Cryptococcus sp. in the phylum Basidiomycota. We provided a genetic database of the fungal ITS-D1(fLSU)s in the differently managed soils of upland rice fields.

Impact of reduced tillage and cover cropping on the greenhouse gas budget of a maize/soybean rotation ecosystem

Agricultural ecosystems have been viewed with the potential to sequester atmospheric carbon dioxide (CO 2) by increasing soil organic carbon (SOC) through reduced tillage and cover cropping practices. There remains considerable uncertainty, however, regarding the carbon (C) sink/source potential of these systems and few studies have examined C dynamics in conjunction with other important greenhouse gases. The objective of this study was to evaluate the impact of an alternative management scenario (reduced tillage and cover cropping) on ecosystem respiration ( R E) and nitrous oxide (N 2O) and methane (CH 4) fluxes in a maize ( Zea mays L.)/soybean ( Glycine max L.) rotation ecosystem in east-central Minnesota, United States. The control treatment was managed using fall tillage with a chisel plow in combination with a tandem disk, and the experimental treatment was managed using strip tillage and a winter rye ( Secal cereale) cover crop. Over the two-year study period (2004–2005), cumulative R E was 222.7 g C m −2 higher in the alternatively managed treatment as a result of increased decomposition of the cover crop residue. N 2O fluxes were similar in both treatments during the 2004 growing season and were 100.1 mg N m −2 higher in the conventional treatment during the 2005 growing season after nitrogen (N) fertilization. N fertilization and fertilizer type were the dominant factors controlling N 2O fluxes in both treatments. CH 4 fluxes were negligible in both treatments and often below the detection limit. Cumulative growing season N 2O losses in the control and experimental treatments, which totalled 38.9 ± 3.1 and 26.1 ± 1.7 g C m −2 when converted to CO 2 equivalents, were comparable to the annual estimates of net ecosystem CO 2 exchange in both treatments. This study further supports that N 2O losses are an important component of the total greenhouse gas budget of agroecosystems. It also suggests that spring cover cropping, without residue removal, has limited C sequestration potential. The results from this study, however, may not necessarily represent equilibrium conditions in the experimental treatment. Rather, they are a measure of the transient response of the system after tillage conversion and cover crop addition. It is expected that the soil microbes will continue to adjust to the reduction in tillage and increased C inputs. Therefore, continued, long-term monitoring is needed to confirm whether the results are representative of equilibrium conditions.

The influence of cover crops and tillage on water and sediment yield, and on nutrient, and organic matter losses in an olive orchard on a sandy loam soil

Is the cover crop practice suitable for soil and water conservation in olive tree cropping? Rainfall, runoff, sediments, nutrient and organic carbon losses from 8 × 60 m plots were measured during four hydrological years (2002–2007) in a field trial, in which two different soil management systems were used to confirm this hypothesis: a cover crop (CC), and conventional tillage (CT). The plots were located in a private olive tree farm on a sandy-loam soil, near Seville, southern Spain. The cover crop, as compared to conventional tillage, efficiently reduced runoff and sediment yield down to tolerable levels, 5.68% of the rainfall being converted to runoff, and the soil loss reaching 0.04 kg m −2 year −1, as the average of four years. Additionally, in the cover crop treatment, the values of the nutrient export either dissolved in the runoff water or adsorbed in the sediment, were lower than the analogous values of the conventional tillage treatment: 0.631 and 0.065 kg m −2 year −1 of organic carbon and nitrogen, respectively, 0.175 and 0.0333 kg m −2 year −1 of soluble K and P, respectively, and 0.010 and 0.002 kg m −2 year −1 of available K and P, respectively. The adoption of a cover crop as a soil management practice can be a feasible way to reach sustainability in many olive-cropped soils of southern Spain, although this method is not always easy to implement due to technical problems such as seed selection, its maintenance, and the choice of the correct killing date to avoid water competition. These difficulties could explain the slow rate of its adoption by many farmers. Further exploration of these aspects is required, as well as a specific agricultural extension campaign.

Biofuels, Land Use Change, and Greenhouse Gas Emissions: Some Unexplored Variables

Greenhouse gas release from land use change (the so-called "carbon debt") has been identified as a potentially significant contributor to the environmental profile of biofuels. The time required for biofuels to overcome this carbon debt due to land use change and begin providing cumulative greenhouse gas benefits is referred to as the "payback period" and has been estimated to be 100-1000 years depending on the specific ecosystem involved in the land use change event. Two mechanisms for land use change exist: "direct" land use change, in which the land use change occurs as part of a specific supply chain for a specific biofuel production facility, and "indirect" land use change, in which market forces act to produce land use change in land that is not part of a specific biofuel supply chain, including, for example, hypothetical land use change on another continent. Existing land use change studies did not consider many of the potentially important variables that might affect the greenhouse gas emissions of biofuels. We examine here several variables that have not yet been addressed in land use change studies. Our analysis shows that cropping management is a key factor in estimating greenhouse gas emissions associated with land use change. Sustainable cropping management practices (no-till and no-till plus cover crops) reduce the payback period to 3 years for the grassland conversion case and to 14 years for the forest conversion case. It is significant that no-till and cover crop practices also yield higher soil organic carbon (SOC) levels in corn fields derived from former grasslands or forests than the SOC levels that result if these grasslands or forests are allowed to continue undisturbed. The United States currently does not hold any of its domestic industries responsible for its greenhouse gas emissions. Thus the greenhouse gas standards established for renewable fuels such as corn ethanol in the Energy Independence and Security Act (EISA) of 2007 set a higher standard for that industry than for any other domestic industry. Holding domestic industries responsible for the environmental performance of their own supply chain, over which they may exert some control, is perhaps desirable (direct land use change in this case). However, holding domestic industries responsible for greenhouse gas emissions by their competitors worldwide through market forces (via indirect land use change in this case) is fraught with a host of ethical and pragmatic difficulties. Greenhouse gas emissions associated with indirect land use change depend strongly on assumptions regarding social and environmental responsibilities for actions taken, cropping management approaches, and time frames involved, among other issues.

The gap between cover crop knowledge and practice

C over crops can provide a multitude of environmental benefits, including reducing soil erosion, minimizing nitrogen leaching, and increasing soil carbon storage (Delgado et al. 2007; Singer et al. 2007; Hargrove 1991). Cover crops also have the potential to suppress weeds, control pests, and create new sources of income for farmers (Clark 2007). However, cover cropping is not widely practiced (Singer et al. 2007). So why aren't more farmers using cover crops? The key to greater adoption of cover crops likely involves a combination of approaches. Singer et al. (2007) found that “approximately 56% of farmers indicated that they would plant cover crops if cost-sharing was available.” This suggests that cost-sharing mechanisms could be effective as one approach in a successful cover crop implementation toolbox. More can also be done to translate the decades of cover crop research into practical information for producers. The Soil and Water Conservation Society has supported the sharing of information about cover crop research and practice over the years with several conferences and numerous publications on the topic. The Midwest Cover Crops Council is currently conducting a survey to assess cover crop experience in the Great Lakes and Upper Mississippi region. The information will be used …

The gap between cover crop knowledge and practice

The gap between cover crop knowledge and practice

Sustaining Soil Quality with Legumes in No‐Tillage Systems

Tillage, cropping system, and cover crops have seasonal and long‐term effects on the nitrogen (N) cycle and total soil organic carbon (C), which in turn affects soil quality. This study evaluated the effects of crop, cover crop, and tillage practices on inorganic N levels and total soil N, the timing of inorganic N release from hairy vetch and soybean, and the capacity for C sequestration. Cropping systems included continuous corn (Zea mays L.) and stalk residue, continuous corn and hairy vetch (Vicia villosa Roth), continuous soybeans (Glycine max L.) plus residue, and two corn/soybean rotations in corn alternate years with hairy vetch and ammonium nitrate (0, 85, and 170 kg N ha−1). Subplot treatments were moldboard plow and no tillage. Legumes coupled with no tillage reduced the N fertilizer requirement of corn, increased plant‐available N, and augmented total soil C and N stores.

Limitations and Possibilities for Some Conservation Tillage Systems with Vegetable Crops in the Southern Plains of the United States

We conducted several experiments to determine the best system for production of spring cabbage (Brassica oleracea L. Capitata group) with conservation tillage (CT) in the southern plains of the United States. Rye (Secale cereale L.) was selected as the best cover crop to cover the soil in a short time. Raised beds were formed in the fall and planted with rye. With most studies, the rye was allowed to remain on the soil surface rather than being tilled into the soil. Planting densities, rates of nitrogen fertilizer, and herbicide materials were evaluated to determine the best system for cabbage production. In each study, various cover crop practices were compared with bare soil production systems. Soil erosion was reduced by the use of rye cover crops. Cabbage was produced in the CT system, but cabbage yields were higher in bare soil plots than in the rye-covered plots. We are also in the process of developing a system of CT that involves permanent bermudagrass [Cynodon dactylon (L.) Pers.] pastures and watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai]. This system allows both crops to be grown simultaneously on the same land.

Cover-cropping Practices of Vegetable Producers in Western New York

Surveys of vegetable growers in a six-county region in western New York were conducted in 1997 to determine which cover cropping practices were being used on commercial vegetable operations; to identify producers' needs for further research and information, and to assess the impact of cooperative extension programs in this area. In a broad survey, 118 responses were returned out of 315 surveys sent (37%). Respondents represented >37,000 acres (14974 ha) of vegetable production, or ≈53% of the vegetable acreage in the region. Vegetable acreage per operation ranged from 1 to 4000 acres (0.4 to 1619 ha). Sixty-nine percent responded that they grew cover crops on a total of 15,426 acres (6243 ha). Oats (Avena sativa L.), rye (Secale cereale), clover (Trifolium pratense), and wheat (Triticum vulgare) were the most commonly used cover crops. Seventy-six percent of the reported cover-cropped acres were planted to small grains, and 19% to legumes, almost entirely clovers. In open ended questions, the most important benefits of cover cropping identified by respondents were erosion control (46% of respondents) and organic matter additions (42%). The most important problems associated with cover crops were that they interfere with spring field work or fall harvest (26%), and that they are difficult to incorporate or plow under (24%). A targeted survey of nineteen onion (Allium cepa L.) producers in the same region measured the recent adoption of sudangrass (Sorghum sudanense Piper) and sorghum-sudan hybrid (Sorghum bicolor L. × S. sudanense) cover crops, the focus of the several years of extension research and educational programs. Nine of the onion producers had adopted the practice, and six of these had done so since the beginning of these extension programs. The implications of these results for research and extension are discussed.

Alternative Weed Management Systems for the Production of Kidney Beans (Phaseolus vulgaris)

Weed management experiments with kidney beans were conducted at one irrigated site in 1991 and at two irrigated sites near Staples, MN during 1992. Green foxtail was the most difficult weed to control at the three research sites which agrees with survey results from dry bean growers regarding their worst weed problems. Hairy nightshade increased rapidly when weed management methods were reduced. Dry bean seed yields were highest in cultivated check plots on the farmer's field and in conventional practices plots at the Irrigation Research Center. Net economic returns, averaged over 1991 and 1992, for producing kidney beans at the Irrigation Research Center were $899/ha using conventional practices, $791/ha with cover crop practices, $734/ha with cultivated checks, $690/ha with herbicides only, and $208/ha on weedy checks. Kidney beans are an economical crop for North Central growers, but adequate weed management technologies are necessary for profitable production.

Influence of Cover Cropping and No-Tillage Practices on Community Composition of Soil Arthropods in a North Carolina Agroecosystem

Winter legume and grain cover crops preceding corn, Zea mays L., grown using conventional and no-tillage methods were investigated for their effect on population dynamics and community structure of soil arthropods. Hairy vetch, Vicia villosa Roth, supported higher below-ground arthropod population densities and a more taxonomically diverse fauna than crimson clover, Trifolium incarnatum L., or wheat, Triticum aestivum L. Pest and beneficial soil arthropods were most abundant in no-tillage corn preceded by hairy vetch. Diversity of soilarthropod species was higher under no-tillage than conventional tillage. Divergences in community structure of soil arthropods among cover crop species, evident early in the season, dissipated by midseason. Arthropod predators were more numerous in no-tillage than conventional tillage systems regardless of previous cover crops. Although no-tillage practices promoted a more trophically balanced soil arthropod community than conventional tillage during early and mid season, in 1987 seedling corn plants in no-tillage vetch treatments sustained significantly higher (P < 0.05) damage from the southern corn rootworm, Diabrotica undecimpunctata howardi Barber, than in other treatments. Tillage system preference was shown by herbivores: Seedcorn maggot, Delia platura (Meigen), occurred in large numbers in conventional tillage, and southern corn rootworm populations were high in no-tillage, especially following legume cover crops.

Control of the Black Vine Weevil on Concord Grapes in Central Washington1

Four granular insecticides were evaluated during 1962 in replicated plots for control of the black vine weevil, Brachyrhinus sulcatus (F.). Aldrin at 3.2, 3.9, 4.9, and 5.6 lb actual per acre, dieldrin at 3 lb, endrin at 2 lb, and Imidan® (phthalimidomethyl- O,O -dimethyl phosphorodithioate) at 2 lb were applied to the soil surface of a vineyard having 5 different cover-crop cultural practices. Applications were made in late May and early June before the adult weevils had emerged. Aldrin at the 4.9- and 5.6-lb rates was most effective. In another experiment where 5 lb actual aldrin granules was compared with a malathion (2.4 lb) plus aldrin (0.25 lb) dust mixture, the aldrin was most effective. In aldrin-treated vineyards mean cluster injuries were less than 1 per cluster and injured berries were less than 1% compared with mean cluster injuries as high as 25 per cluster and up to 54% injured berries in untreated vineyards or those treated with a malathion-aldrin dust mixture. Contact with aldrin granules disrupts the normal behavior pattern of adult weevils so that rather than hiding by day they are found wandering on the soil surface at mid-morning. Adult weevils were killed in the laboratory when subjected to a temperature of 90°F for several hours. Factors responsible for weevil mortality in the vineyard appear to be a combination of toxic effects of aldrin and high soil-surface temperature. Weevils taken early in the morning from a vineyard treated recently with aldrin were kept at room temperature with adequate food for 30 days, indicating that effects of aldrin alone were not lethal.