Cover crops used in red raspberry plantings (Rubus idaeus L.) are often good hosts of the root-lesion nematode (Pratylenchus penetrans Filipjev & Sch. Stekoven), a major soilborne pathogen of raspberry. The effects of two susceptible cover crops, white clover (Trifolium repens L.) and barley (Hordeum vulgare L.), planted in between rows, on nematode density and growth of raspberry plants were compared to those of three cover crops resistant to the nematode: redtop (Agrostis alba L.), creeping red fescue (Festuca rubra L.), and `Saia' oat (Avena sativa L.). Nematode multiplication in raspberry roots and in cover crop roots was assessed over 4 years. Growth and vigor of plants were estimated at the end of the experiment by counting primocanes and determining height and biomass. Nematode multiplication was suppressed in roots of `Saia' oat, fescue, and redtop compared to barley or white clover. Nematode density in roots and rhizosphere soil of raspberry was not affected by the choice of cover crops. Nematode suppression in the three resistant cover crops did not translate into increased vigor of raspberry plants.
Thierry Vrain, Robyn DeYoung, John Hall and Stan Freyman
Wayne F. Whitehead and Bharat P. Singh
The objective of this study was to determine if winter legume or grain cover could support net photosynthesis (Pn) and plant dry matter production comparable to recommended rate of synthetic N. The following winter/spring fertility treatments were applied: 1) 0 N winter/0 N spring, 2) 0 N winter/90 kg·ha–1 N spring, 3) 0 N winter/180 kg·ha–1 N spring, 4) 0 N winter+abruzi rye/0 N spring, 5) 0 N winter+hairy vetch/0 N spring, and 6) 0 N winter+crimson clover/0 N spring. `Mountain Pride' tomato was planted in all plots in spring. Plant dry weight and Pn were measured at flowering, fruiting and prior to senescence. The highest Pn (22.78 μmol CO2/m2 per s) and leaf dry weight (115.2 g/plant) were obtained at fruiting, while highest branch dry weight (194.5 g/plant) occurred prior to senescence. There was significant increase in plant dry weight during reproductive growth phase. Tomato plants receiving supplemental N from crimson clover or hairy vetch had Pn and plant dry weight comparable to those receiving synthetic N. The results of this study indicated that legume cover crops were as effective as commercial N fertilizer for supporting photosynthesis and vegetative growth of tomato.
John R. Teasdale and Aref A. Abdul-Baki
Hairy vetch (Vicia villosa Roth), crimson clover (Trifolium incarnatum L.), and rye (Secale cereale L.) and mixtures of rye with hairy vetch and/or crimson clover were compared for no-tillage production of staked, fresh-market tomatoes (Lycopersicon esculentum Mill.) on raised beds. All cover crops were evaluated both with or without a postemergence application of metribuzin for weed control. Biomass of cover crop mixtures were higher than that of the hairy vetch monocrop. Cover crop nitrogen content varied little among legume monocrops and all mixtures but was lower in the rye monocrop. The C:N ratio of legume monocrops and all mixtures was <30 but that of the rye monocrop was >50, suggesting that nitrogen immobilization probably occurred only in the rye monocrop. Marketable fruit yield was similar in the legume monocrops and all mixtures but was lower in the rye monocrop when weeds were controlled by metribuzin. When no herbicide was applied, cover crop mixtures reduced weed emergence and biomass compared to the legume monocrops. Despite weed suppression by cover crop mixtures, tomatoes grown in the mixtures without herbicide yielded lower than the corresponding treatments with herbicide in 2 of 3 years. Chemical name used: [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one](metribuzin).
Derek M. Law and Brent Rowell
A 2-yearfield study in Lexington, Ky., evaluated the use of mulches in two organic production systems for bell peppers. Two planting strategies, flat ground and plastic-covered raised beds, and five weed control practices, straw mulch, compost mulch, wood chip mulch, corn gluten, and “living mulch” clover were tested. In 2003, the mulches were applied at planting, while in 2004, shallow soil cultivation was used for 6 weeks prior to mulch application. In 2003, the experimental field had been under a winter wheat cover crop; in 2004, the field had been cover cropped for more than a year prior to planting with sudex/cowpea (Summer 2003) and rye/hairy vetch (Winter/Spring 2004). Bell pepper yields in both bed treatments were very low in 2003 due to extensive weed competition. In 2004, plastic-covered raised beds coupled with mulching in-between beds resulted in significantly higher yields than the peppers grown on flat ground. These yields were as high as yields from a conventional pepper trial conducted on the same farm. Compost mulch, continuous cultivation, and wood chip mulch provided excellent weed control in 2004. Straw mulch was variable in its weed control efficacy; corn gluten and “living mulch” clover were ineffective.
Clyde L. Elmore, Scott Steinmaus and Dean Donaldson
Cover crops are grown in vineyards for many reasons, including erosion control, maintaining organic matter and changing pest complexes. Changing a management practice from using resident vegetation as a cover to other planted cover crops will change the vineyard floor flora. The cover crops of `Olge' oat, `Olge' oat and purple vetch, and purple vetch alone were compared to resident vegetation as winter planted cover crops. The cover was harvested in April of each year and blown under the vine row; The cover crop remains were disked into the middles after mulching. Three varieties of subterranean clover were planted in the vine rows at each location in one-half of each of the cover crops. The winter annual weed species, black and wild mustard, common chickweed and annual bluegrass decreased in the inter-row areas. The perennial weed field bindweed increased in all cover crop treatments.
Dale T. Lindgren
Wildflowers/native plants are increasingly being used in landscapes, especially in low maintenance areas. Buffalograss is also receiving attention as a low maintenance grass. Establishing wildflowers in buffalograss would be useful in sites where mowing occurred only once in the fall, such as with minimeadows. Four experiments were conducted to study the establishment of wildflowers in buffalograss. Survival of wildflowers after one year was 88% when wildflowers were planted as greenhouse grown transplants and buffalograss plugged in 2 weeks later, 67% when one-year-old field grown wildflowers were transplanted into buffalograss plugged at the same time and 48% when greenhouse grown wildflowers were transplanted into established buffalograss. Establishment of wildflowers overseeded into established buffalograss sod was very low. There were significant differences in wildflower survival within each study. Species which performed well in buffalograss included Leadplant, Blue Fax, Purple Prairie Clover, Little Bluestem and Stiff Goldenrod.
R. Provvidenti and R.O. Hampton
Resistance to white lupin mosaic virus (WLMV), a recently characterized member of the potyvirus group, was found in pea (Pisum sativum L.) plant introductions from Ethiopia (PI 193835) and India (PI 347485). In cross and backcross populations between plants of resistant PI 193835 with those of susceptible `Bonneville' and PP-492-5, this resistance was demonstrated to be governed by a single recessive gene. This gene was distinct from other genes previously found in PI 193835 and PP-492-5 (from PI 347492, India) conferring resistance to clover yellow vein virus (CYVV) and three strains of pea seedborne mosaic virus (PSbMV). Indirect evidence suggests that this newly recognized viral resistance gene, wlv, is a member of a cluster of closely linked genes located on chromosome 6. This gene cluster includes sbm-1, sbm-3, and sbm-4, which govern resistance to three PSbMV pathotypes, and cyv-2, which governs resistance to CYVV.
N.R. Rice, M.W. Smith, R.D. Eikenbary, D.C. Arnold, W.L. Tedders, B.W. Wood, G.G. Taylor, B.S. Landgraf and G.E. Barlow
Annual legume ground covers were evaluated in pecan (Carya illinoinensis) orchards to supply nitrogen and increase beneficial arthropods. Treatments were established at two sites, each with 5 ha of a `Dixie' crimson clover (Trifolium incarnatum) /hairy, vetch (Vicia villosa) mixture and 5 ha of grass sod. Data indicated that the legume mixture supplied over 100 kg·ha-1 N to the pecan trees. Beneficial arthropods were greater in orchards with legume ground covers than in orchards with a grass groundcover. Lady beetles and green lacewings were the most important spring predators, and green lacewings were the most important fall predator. The Species distribution on the ground covers differed from that in the canopy. Coleomegilla maculata lengi, Hippodamia convergens and Coccinella septempunctata were the most abundant lady beetle species in the legume ground covers, and Olla v-nigrum, Cycloneda munda, and Hippodamia convergens were the most abundant species in the pecan canopies. Beneficial arthropods appeared to suppress injurious pecan aphids.
Pat Bowen and Stan Freyman
Raspberries (Rubus idaeus L.) were grown for 5 years with three floor management treatments: clean cultivation (CC) and ground covers of white clover (Trifolium repens L.) (WC) and perennial ryegrass (Lolium perenne L.) (PR). Primocane growth was strongest with WC and weakest with PR. Fruit production did not differ between WC and CC treatments and was higher than with PR. On 22 Aug. and 10 Sept. in the last year, primocanes grown with WC were taller, had more nodes and a higher dry weight, contained more N, and had retained more leaves than those grown with PR. Net CO2 assimilation per unit leaf area was higher with WC than with PR, and the difference was greater at the more proximal position. The estimated net CO2 assimilation rate per primocane was more than twice as high with WC than with PR.
Aref A. Abdul-Baki, J.R. Teasdale, R. Korcak, D.J. Chitwood and R.N. Huettel
A low-input sustainable agricultural system for the production of staked, fresh-market field tomatoes (Lycopersicon esculentum Mill.) is described. The system uses winter annual cover crops to fix N, recycle leftover nutrients, produce biomass, and prevent soil erosion throughout the winter and spring. Yields of tomato plants grown in hairy vetch (Vicia villosa Roth), crimson clover (Trifolium incarnatum L.), and rye (Secale cereale L.) plus hairy vetch mulches were higher than those grown in the conventional black polyethylene (BP) mulch system in 2 of 3 years. Fruit were heavier with the plant mulches than with BP mulch. Eight weeks after transplanting, N levels in tomato leaves were higher with plant than with BP mulch, although the plant mulch plots received only 50% of the N applied to the BP plots. The cover crops had no effect on populations of five phytoparasitic nematode species.