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Richard L. Harkess and Robert E. Lyons

Combinations of seeding rate, spacing, and weed control treatments were evaluated for their effect on the performance of the Virginia Tech transplanted meadow technique. The treatments consisted of seeding at 112 or 56 g·90 m−2; within-row transplant spacing of 30, 45, or 60 cm; and mulching, oryzalin application, or no weed control measures. Plant competition alone was insufficient, whereas oryzalin was the most effective for weed control but also reduced the plant stand and floral display. Mulch provided effective weed control with maximum floral display. Close transplant spacing within rows resulted in quick site coverage initially, but this advantage disappeared after 8 weeks compared to wider spacing. Seeding rate did not affect site coverage until the meadow reached maturity at 12 weeks. The lower seed rate allowed more lodging, resulting in a more open appearance and greater canopy light transmission. Chemical name used: 4-(dipropylamino)-3,5-dinitrobenzenesulfonamide (oryzalin).

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Craig A. Dilley, Gail R. Nonnecke, and Nick E. Christians

Alternative approaches to strawberry production that rely on cultural practices, biological controls, or natural products to reduce or replace off-farm chemical inputs are needed. Driving this growing interest are environmental concerns and rising production costs. Corn gluten meal (CGM), a byproduct of corn wet-milling, has weed-control properties and is a N source. The weed control properties of CGM have been identified in previous studies. The hydrolysate is a water-soluble, concentrated extract of CGM that contains between 10% to 14% N. Our objective was to investigate corn gluten hydrolysate as a weed control product and N source in `Jewel' strawberry production. The field experiment was a randomized complete block with a factorial arrangement of treatments and four replications. Treatments included application of granular CGM, CGM hydrolysate, urea, urea, and DCPA (Dacthal), and a control (no application). Granular CGM and urea were incorporated into the soil at a depth of 2.5 cm at rates of 0, 29, 59, and 88 g N/plot. Plot size was 1 × 3 m. The field experiment was conducted from 1995-1998. The source of nitrogen showed few effects for all variables measuring yield and weed control for all years. In general, the rate of nitrogen had little or no effect on total yield. However, the rate of nitrogen at 88 g N/plot showed an increase in average berry weight, leaf area, leaf dry weight, and weed control.

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Joseph G. Masabni and Dwight E. Wolfe

Flumioxazin (Chateau 51WG) is an herbicide for the preemergence and early postemergence control of broadleaves and grasses. Chateau was recently labeled for use in non-bearing fruit trees and bearing grapes. Long-term weed control in apple, peach, and blueberry was investigated following fall application of herbicides. Treatments consisted of simazine 2.8 kg a.i., norflurazon 2.24 kg a.i., napropamide 2.24 kg a.i., and oryzalin 2.24 kg a.i. were applied on 11 Nov. 2003. Flumioxazin was also applied at 0.1 and 0.43 kg ai on apple and peach. All treatments included glyphosate 1 lb a.i. for burndown control of preexisting weeds. Weed control evaluation in mid-April or 4 months after application showed that flumioxazin-treated plots had no weeds present and no weed regrowth. Plots treated with napropamide, norflurazon, and oryzalin showed significant regrowth of dandelion, common ragweed, and chickweed. Simazine plots had fewer weeds germinating than the other herbicides. By early June or 6 months after application, no differences in residual weed control were observed for all treated plots when compared to the control. All plots were equally weedy and required immediate floor management measures. It appears that flumioxazin weed control benefit was exhausted by 6 months after application, compared to 4 months for all other herbicides. Fall application of flumioxazin can eliminate the need for early spring weed control. This time saved can be spent on other important activities such as pruning and disease and insect control.

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J.W. Van Sambeek and John E. Preece

Hybrid poplar is traditionally established using dormant stem cuttings in tilled soils followed by chemical or mechanical weed control. In 1996, we initiated a study to evaluate the effects of site preparation and four weed control treatments on growth and morphology of three hybrid poplar clones established on a 0.2-ha tall fescue field in southern Illinois. Site preparation included application of 2000 kg/ha of 12N-12P-12K. The experiment was arranged as a split-split plot. Main plots were closely mowed tall fescue or tilled to remove the grass sod. Within each main plot, weed control treatments were applied to 1-m wide strips in rows 2.4 m apart. Weed control treatments included porous black film, solid black film, and solid white film, and a control treatment of 3.7 L/ha of glyphosate applied each spring. On 15 Apr. 1996, three 25-cm-long dormant stem cuttings from each of three clones were randomly planted 15 cm deep every 1.8 m within each row. Clonal differences existed after the first year for survival, number of stems, stem height, stem basal diameter, and stem volume, but not for number and total length of lateral branches. Nearly all tree growth measurements analyzed during the first 3 years had a highly significant interaction between type of site preparation and method of weed control. With polyethylene films, tree survival exceeded 90% on both the tilled ground and grass sod sites after 3 years; however, with the herbicide treatment survival averaged only 18% in the grass sod and 51% in tilled soil. Excluding the herbicide treatment, tree growth was better in the grass sod than in the tilled soil. Tree growth using porous black polyethylene film was usually less than that with either of the two solid polyethylene films. The best tree growth was found with a grass sod and solid white polyethylene film for weed control.

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Jacqueline A. Ricotta and John B. Masiunas

Black polyethylene mulch and weed control strategies were evaluated for potential use by small acreage herb producers. In both 1988 and 1989, the mulch greatly increased fresh and dry weight yields of basil (Ocimum basilicum L.) and rosemary (Rosmarinus officinalis L.). Parsley (Petroselinum crispum Nym.) yield did not respond to the mulch. Preplant application of napropamide provided weed control for 2 weeks, but was subsequently not effective on a heavy infestation of purslane (Portulaca oleracea L.). Hand-hoed and glyphosate-treated plots (both with and without plastic) produced equivalent yields. Chemical names used: N, N -diethyl-2(1-napthalenoxy)-propanamide (napropamide); N- (phosphonomethyl) glycine (glyphosate).

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S. Alan Walters, Scott A. Nolte, and Bryan G. Young

The influence of `Elbon', `Maton', and `Wheeler' winter rye (Secale cereale) with or without herbicide treatments on weed control in no-tillage (NT) zucchini squash (Cucurbita pepo) was determined. `Elbon' or `Maton' produced higher residue biomass, greater soil coverage, and higher weed control compared with `Wheeler'. Although winter rye alone did not provide sufficient weed control (generally <70%), it provided substantially greater redroot pigweed (Amaranthus retroflexus) and smooth crabgrass (Digitaria ischaemum) control (regardless of cultivar used) compared with no winter rye at both 28 and 56 days after transplanting (DAT). No effect (P > 0.05) of winter rye cultivar on early or total squash yield was detected. Although applying clomazone + ethalfluralin to winter rye residues improved redroot pigweed control compared with no herbicide, the level of control was generally not adequate (<85% control) by 56 DAT. Treatments that included halosulfuron provided greater control of redroot pigweed than clomazone + ethalfluralin, and redroot pigweed control from halosulfuron treatments was similar to the weed-free control. However, regardless of year or cover crop, any treatment with halosulfuron caused unacceptable injury to zucchini squash plants which lead to reduced squash yield (primarily early yields). Insignificant amounts of squash injury (<10% due to stunting) resulted from clomazone + ethalfluralin in no-tillage plots during either year. Treatments with clomazone + ethalfluralin had early and total yields that were similar to those of the weed-free control, although this herbicide combination provided less weed control compared with the weed-free control.

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Edmund J. Ogbuchiekwe and Milton E. McGiffen Jr.

Economic analyses compared the returns of weed control methods for drip and sprinkler irrigated celery (Apium graveolens L. `Sonora'). The nine treatments included an untreated control, cultivation as needed for weed control, a pre-emergent herbicide (trifluralin), and six post-emergent herbicides. The effect of each treatment on weed control, yield, crop value, cost of control, costs for additional hand-weeding, net return, and dollar investment (marginal rate of return) was determined. The treatments that reduced weed populations under drip and sprinkler irrigation also increased yield, net returns, and rate of returns. Effective weed control reduced the additional costs of hand-hoeing the weeds not killed by herbicides, resulting in greater net return. The net returns of weed control were even greater when celery was drip irrigated than when sprinklers were used. In 1998, the sprinkler irrigated field returned $1148 to $3921/ha, compared with -$5984 for the untreated control. Net returns for drip irrigation were much higher, ranging from $3904 to $9187/ha compared with -$8320 for the untreated control. Net returns were also higher in 1999, ranging from $2466 to $5389 when weeds were controlled compared with a net loss of $5710 for the untreated control in the sprinkler irrigated field. The returns on the drip-irrigated field were much higher, from $6481 to $8920 when weeds were controlled, compared with -$8046 for the untreated control. The associated returns for every dollar invested (marginal rate of return) in the non-dominated treatment (more return and lower cost) ranged from 52% to 156% for sprinkler irrigation, and 59% to 144% for drip irrigation in 1998. In 1999, the rate of return for each dollar invested ranged from 104% to 324% for sprinkler and 2.4% to 321% for drip irrigated fields.

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Derek M. Law, A. Brent Rowell, John C. Snyder, and Mark A. Williams

A 2-year field study in Lexington, Ky., evaluated weed control efficacy and influence on yields of several organic mulches in two organically managed bell pepper (Capsicum annuum) production systems. Five weed control treatments [straw, compost, wood chips, undersown white dutch clover (Trifolium repens) “living mulch,” and the organically approved herbicide corn gluten] were applied to two production systems consisting of peppers planted in double rows in either flat, bare ground or on black polyethylene-covered raised beds. In the first year, treatments were applied at transplanting and no treatment was found to provide acceptable season-long weed control. As a result, bell pepper yields in both production systems were very low due to extensive weed competition. First year failures in weed control required a modification of the experimental protocol in the second year such that treatment application was delayed for 6 weeks, during which time three shallow cultivations were used to reduce early weed pressure and extend the control provided by the mulches. This approach increased the average weed control rating provided by the mulches from 45% in 2003 to 86% in 2004, and resulted in greatly improved yields. In both years, polyethylene-covered raised beds produced higher yields than the flat, bare ground system (8310 lb/acre compared to 1012 lb/acre in 2003 and 42,900 lb/acre compared to 29,700 lb/acre in 2004). In the second year, the polyethylene-covered bed system coupled with mulching in-between beds with compost or wood chips provided excellent weed control and yields. When using the wood chip mulch, which was obtained at no cost, net returns were $5587/acre, which is similar to typical returns for conventionally grown peppers in Kentucky. Net returns were substantially decreased when using compost due to the purchase cost. Results from this study indicate that shallow cultivation following transplanting, combined with midseason mulch application, resulted in high yields in an organically managed bell pepper system that were comparable to yields of most varieties grown conventionally in a variety trial conducted on the same farm.

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Carl E. Bell, Brent E. Boutwell, Edmund J. Ogbuchiekwe, and Milton E. McGiffen Jr.

Application of linuron was compared with hand-weeding and a nontreated control (= control) for weed control in carrots. Linuron, applied pre- or postemergent, was slightly less effective than the 100% weed control obtained by hand-weeding. Carrot yields were similar for all treatments, and were at least six times as great as in the control. In 1996, linuron treatments returned net profits ranging from $980 to $1887 per ha, compared to $740 for hand-weeding and -$2975 for the control. In 1997, return on linuron treatments was greater, ranging from $5326 to $6426, compared with $2852 for hand-weeding. Marginal rates of return ranged from 21% to 86% in 1996. In 1997, rates of return for every dollar invested in linuron were over 59%. Chemical name used: N′-(3,4-dichlorophenyl)-N-methoxy-N-methylurea (linuron).

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Carl E. Bell, Brent E. Boutwell, Edmund J. Ogbuchiekwe, and Milton E. McGiffen Jr.

Application of linuron was compared with hand-weeding and a nontreated control (= control) for weed control in carrots. Linuron, applied pre- or postemergent, was slightly less effective than the 100% weed control obtained by hand-weeding. Carrot yields were similar for all treatments, and were at least six times as great as in the control. In 1996, linuron treatments returned net profits ranging from $980 to $1887 per ha, compared to $740 for hand-weeding and - $2975 for the control. In 1997, return on linuron treatments was greater, ranging from $5326 to $6426, compared with $2852 for hand-weeding. Marginal rates of return ranged from 21% to 86% in 1996. In 1997, rates of return for every dollar invested in linuron were over 59%. Chemical name used: N′-(3,4-dichlorophenyl)-N-methoxy-N-methylurea (linuron).