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Braja B. Datta and Ray D William

Fall-planted cover crops killed in spring is practiced in strawberry cultivation in different regions of the North America. These systems have shown significant weed suppression and conservation of soil without significant yield reduction in strawberry. During the establishment season, this study was initiated to assess weed suppression with cover crops (`Wheeler' rye and `Micah' and `Steptoe' barley) along with perlite, an artificial plant medium. Strawberry (`Selva' and `Totem') plant growth and weed biomass were measured during 1995-96 season. Small-seeded summer annual weeds were suppressed in cover crop treatments compared to control treatment. `Micah' barley in growth phase suppressed more than 81% of the total weed biomass compared to control plots with no cover crop in early spring. However, in early summer, cover crop residues failed to suppress different types of weeds 60 days after killing of cereal with herbicide (2% glyphosate). Distinct differences in strawberry plant growth were evident between the cover crop treatments and non-cover crop treatments including `Micah' applied on surface. Strawberry growth was doubled during 10 July to 15 Aug. in both cultivars. `Micah' barley applied on surface produced better growth in both strawberry varieties than the growth in other treatments. `Micah' barley applied on soil surface produced 50% more strawberry shoot biomass may indicate the root competition between cover crops and strawberry.

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Nancy G. Creamer and Mark. A. Bennett

A mixture of rye, hairy vetch, barley, and crimson clover was seeded on raised beds at two locations in Ohio in August, 1992. The following May, the mixture was killed with an undercutter and left on the surface as a mulch. Processing tomatoes (OH 8245) were planted into the killed cover crop mulch immediately following undercutting. Four systems of production were evaluated including: conventional (without cover crop mulch), integrated (with reduced chemical input), organic, and no additional input. At the Columbus site, above ground biomass (AGB) was 9,465 kg ha-1 with 207 kg ha-1 N in to AGB. In Fremont, the AGB was 14,087 kg ha-1 with 382 kg ha-1 N in the AGB. Annual weeds were suppressed by the killed cover crop mulch, and no additional weed control for the annual weeds was necessary. Weed suppression by the mulch was equivalent to weed suppression by the herbicides used in the conventional system. Other data that will be reported include soil moistures and temperatures; impact on insects end diseases; and, tomato growth, development, and yield.

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Orion P. Grimmer and John B. Masiunas

Winter-killed oats (Avena sativa) may have potential for use to suppress weeds in early seeded crops such as pea (Pisum sativum). Residue biomass and surface coverage are generally correlated with weed suppression. Oat residues also contain allelochemicals. Our objective was to determine if oat cultivars vary in residue production and allelopathy. Differences between oat cultivars were observed in residue production, and for effects on emergence of common lambsquarters (Chenopodium album) and shepherd's-purse (Capsella bursa-pastoris) in the greenhouse, and germination of pea and common lambsquarters in an infusion assay. Two of the oat cultivars producing the greatest biomass, `Blaze' (in the field) and `Classic' (in the greenhouse), interfered minimally with pea germination and were among the best cultivars in inhibiting common lambsquarters and shepherd's-purse. `Blaze' also greatly inhibited common lambsquarters germination in the infusion assay that measured allelopathy. Thus, `Blaze' and `Classic' possess suitable characteristics for use as a cover crop preceding peas.

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Martin F. Quigley

Six durable but slow-to-establish groundcover species, and three fast-growing but short-lived groundcover species, were planted singly and in paired combinations under mature landscape trees to test for relative weed suppression. Installations were replicated on an urban site and a rural site, monitored for two growing seasons, and weeded periodically by hand. All weeds were dried and weighed, and subplot averages (160 observations) for each plant combination were tested by analysis of variance. Weeds were significantly fewer and smaller in the mixed species than in single species subplots. Weed biomass was also significantly less in monospecific groundcover subplots than in unplanted control plots. These results suggest that reduced maintenance cost (and input) for weed control, along with better initial coverage appeal of the paired plantings, may increase marketability of perennial groundcovers.

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Mathieu Ngouajio

Over the last century, climate change, adoption of new regulations, and changes in cropping systems have significantly impacted weed and pest management in horticultural crops. The objective of this workshop was to provide a critical review of major changes and discuss current and future trends for weed and pest management. Speakers touched on a broad range of topics including climate change and disease dynamics, the use of disease resistance inducers, soil management for pest management, and the role of allelopathy in weed management. Major recommendations included 1) increased grower education related to the impact of climate change on plant diseases; 2) more research directed towards a better understanding of the interaction of plant–pathogen–inducer; 3) use of organic soil amendments, cover crops, crop rotations, and resistant cultivars to enhance the weed and disease suppressive effect of soils; and 4) enhancement of allelochemical production and subsequent weed suppression through conventional breeding and molecular techniques.

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H.H. Bryan, A.A. Abdul-Baki, L. Carrera, G. Zinati and W. Klassen

Ground covers in orchards and living mulches in vegetable fields can be effective in reducing weed control costs and loss of water and nutrients from the soil, fixing N, and adding organic matter to the soil. Several accessions of rhizoma (perennial) peanut were evaluated in 1999, 30 months after planting, at the farm of the Tropical Research and Education Center, Univ. of Florida, Homestead, in gravelly, calcareous soil with a pH of 7.5. Evaluation criteria included adaptability (plant vigor, rhizome growth, and biomass yield), weed suppression, N-fixation, nutrient content, leaf density, and Fe chlorosis. Accessions that survived exhibited major differences in the evaluation criteria. Accessions No. 6968 and 4222 (recently named `Amarillo') showed promising potential for use as ground cover and a living mulch in vegetable fields in southern Florida.

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Aref A. Abdul-Baki, Ronald D. Morse, Thomas E. Devine and John R. Teasdale

`Emperor' broccoli (Brassica oleraceae L. Botrytis Group) was grown in Fall 1995 at the Beltsville Agricultural Research Center (BARC), Md., and at the Kentland Agricultural Research Farm (KARF), Virginia Polytechnic Institute and State Univ., Blacksburg. The objectives were to determine the effects of cover crop mulches in no-tillage production systems on marketable broccoli yield and weed suppression. The mulch treatments included cover crops of forage soybean (Glycine max L.), foxtail millet (Setaria italica L.P. Beauv), and a combination of soybean and millet. Broccoli marketable yield from all three mulch treatments was equal to that from a conventional clean cultivation system, except for the millet treatment at BARC, which produced a lower yield. All treatments maintained weeds below levels that reduced yield. Cover crop biomass ranged from 4.6 to 9.6 t·ha-1 and N content from 10 g·kg-1 for millet to 28 g·kg-1 for soybean.

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Charlotte Herman, David Larson and Emily Hoover

The goal of our program is to learn how to effectively establish first-year strawberry plantings without using herbicides. Before strawberry transplanting, four treatments were established: winter wheat, a dwarf Brassica sp., napropamide (2.24 kg·h–1) plus hand hoeing and rototilling, and no weed management. `Honeyoye' transplants were set into plots measuring 6.1 × 7.32 m on 21 May 1993 and 10 May 1994. Weekly data was taken on the percentage of soil area covered with plant material, height, and stage of development of plants, and weeds present. Weed transects and plant dry weights were done periodically during the growing seasons. The most promising cover crop treatment was the dwarf Brassica sp. for early season weed suppression because of rapid germination and short stature. Winter wheat was very competitive with the strawberry plants. The herbicide treatment had the largest inputs; however, it did produce the largest strawberry plants at the end of the season.

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Laura K. Hunsberger

Vegetable soybeans [Glycine max (L.) Merr.] (edamame) are growing in popularity as a niche crop grown by traditional grain producers. Edamame were grown in an organically transitional system from 2004–2005 at the University of Maryland Lower Eastern Shore Research and Education Center in Salisbury, Md. Four weed suppressing treatments were used in order to determine if this crop would grow well in an organic production system. Five varieties; BeSweet 2020S, BeSweet 292, 414F, Dixie (2004 only), and Mooncake (2005 only) were grown in a RCB design with 4 reps. The weed suppression systems included; a ground cover of commercially purchased compost in a 4-inch layer, a ground cover of straw in a 4-inch layer, New Zealand Clover applied as a living mulch at a rate of 35#/A and an untreated control. Soybeans grown in both commercial compost and clover had significantly higher yields (6,606 and 5,578 lb/acre, respectively) than those grown in the untreated control (4,283 lb/acre), but were not different from those grown in straw (5,578 lb/acre). Weed suppression system also had an affect on the pod number per plant. On average, compost, clover and straw had 49% more pods per plant than the control. Over both years, BeSweet 2020S, BeSweet 292, 414F, and Dixie all had significantly higher yields than Mooncake (5,003, 5,613, 5,522, 7,138 and 1,875 lb/acre, respectively). Variety also had an effect on pod number per plant, with BeSweet 2020S having a 37% higher pod number that BeSweet 292. It is feasible that vegetable soybeans can be grown organically or in a low input system. This value added crop could fill an important niche for both market growers and small traditional grain producers growers.

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E.V. Herrero, J.P. Mitchell, W.T. Lanini, S.R. Temple, E.M. Miyao, R.D. Morse and E. Campiglia

No-till processing tomato (Lycopersicum esculentum Mill.) production in four winter cover crop-derived mulches was evaluated in 1997 and 1998 in Five Points, Calif. The effectiveness of two medics, `Sava' snail medic (Medicago scutellata Mill.) (sava), and `Sephi' barrel medic (Medicago truncatula Gaertn.) (sephi), and two cereal/legume cover crop mixtures, triticale/`Lana' woolypod vetch (X Triticosecale Wittm./Vicia dasycarpa Ten.) (triticale/vetch) and rye/`Lana' woolypod vetch (Secale cereale L./V. dasycarpa) (rye/vetch), was compared with two conventionally tilled fallow controls (with and without herbicide) (fallow+h and fallow-h) in suppressing weeds and maintaining yields with reduced fertilizer inputs. The comparison was conducted as a split plot, with three N fertilization rates (0, 100, and 200 lb/acre; 0, 112, and 224 kg·ha-1) as main plots and cover crops and fallow controls as subplots. Tomato seedlings were transplanted 3 weeks after the cover crops had been mowed and sprayed with herbicide. There were no significant differences in weed cover in the no-till cover crop treatments relative to the fallow controls in 1997. Early season weed suppression in rye/vetch and triticale/vetch plots was similar to herbicide-treated fallow (fallow+h) in 1998, however, later in the 1998 season weed suppression was best in the fallow+h. Tissue N was highest in the fallow treatments in both 1997 and 1998. Yields were highest in the triticale/vetch and fallow and lowest in sephi treatments in 1997, but there were no differences among treatments in 1998. These results demonstrate the feasibility of no-till mulch production of furrow irrigated processing tomatoes and identify opportunities for further optimization of the system.