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  • Author or Editor: Brent L. Black x
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Balancing vegetative growth with fruiting is a primary concern in strawberry (Fragaria ×ananassa Duch.) production. Where nursery plant selection and preconditioning are inadequate for runner control, additional approaches are needed. The gibberellin biosynthesis inhibitor prohexadione-Ca (commercial formulation Apogee) was tested over two seasons for suppressing fall runners of `Chandler' plug plants in a cold-climate annual hill production system. Prohexadione-Ca was applied as a foliar spray at active ingredient concentrations ranging from 60 to 480 mg·L-1, either as a single application 1 week after planting, or repeated at 3-week intervals. The lowest rate resulted in inadequate runner control, with some runners producing malformed daughter plants. Higher rates resulted in 57% to 93% reductions in fall runner numbers, with a concomitant increase in fall branch crown formation. There were no effects of the prohexadione-Ca treatments on plant morphology the following spring, and no adverse effects on fruit characteristics or yield. Chemical names used: prohexadione-calcium, calcium 3-oxido-4-propionyl-5-oxo-3-cyclohexene-carboxylate.

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Bottom ash from a coal-fired power plant and two composts were tested as components of soil-free media and as soil amendments for growing highbush blueberry (Vaccinium corymbosum L.). Combinations of ash and compost were compared to Berryland sand, and Manor clay loam, and compost amended Manor clay loam. The pH of all treatment media was adjusted to 4.5 with sulfur at the beginning of the experiment. In 1997, plants of `Bluecrop' and `Sierra' were planted in 15-dm3 pots containing the pH-adjusted treatment media. The first substantial crop was harvested in 1999. At the end of the 1999 season, one half of the plants were destructively harvested for growth analysis. The remaining plants were cropped again in 2000. Yield and fruit size data were collected in both seasons, and leaf and fruit samples were collected in 1999 for elemental analysis. The presence of coal ash or composted biosolids in the media had no detrimental effect on leaf or fruit elemental content. Total growth and yield of both cultivars was reduced in clay loam soil compared to Berryland sand, whereas growth and yield of plants in coal ash-compost was similar to or exceeded that of plants in Berryland sand.

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Mature tart cherry (Prunus cerasus L. ‘Montmorency’) trees in a commercial orchard were subjected to irrigation deficits from pit hardening to harvest during the 2007 and 2008 seasons. Irrigation treatments ranged from 30% to 100% of a commercially managed application rate during the deficit period. Midday stem water potential measurements were significantly different among treatments before harvest. However, fresh weight yield at harvest did not differ significantly among irrigation treatments in either year (P = 0.64). In 2008, the amount of undersized fruit eliminated during packout was significantly higher in the treatments replacing 30% and 47% of the commercial irrigation level (P < 0.001), but only amounted to 2.0% and 1.4% of total yields, respectively. This small increase in undersized fruit did not significantly affect packout. Soluble solids concentration and chroma of intact fruit increased with the severity of the irrigation deficit and were inversely correlated with fruit water content.

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Highbush blueberry plants require low-pH, well-drained sandy soils. To increase the range of sites available for highbush blueberry production, by-products were tested as constituents in soilless media and as soil amendments. By-products, including coal ash, municipal biosolid compost, leaf compost, and acid peat, were combined in different proportions and compared to Berryland sand (alone) and Manor clay loam (alone and compost-amended) for a total of 10 media treatments. The pH of all treatment media was adjusted to 4.5 with sulfur. One-year-old tissue-cultured plants of `Bluecrop' and `Sierra' were planted in 15-L pots containing the pH-adjusted treatment media in 1997, producing their first substantial crop in 1999. For the 1999 crop, ripe fruit was harvested at weekly intervals over 5 weeks. ANOVA for yield indicated a significant cultivar × media interaction. `Bluecrop' appeared more sensitive to media treatment as yields on Manor clay loam were 80% less than on Berryland sand. Yields of `Bluecrop' on coal ash-compost mixes were similar to that of Berryland sand, and 1:1 coal ash:compost mixes produced significantly higher yields than did the 3:1 mixes. Yield of `Sierra' on Manor clay loam was 41% less than on Berryland sand, and plants growing on soilless mixes yielded 17% to 58% more than those on Berryland sand. `Bluecrop' fruit size was greatest for Berryland sand, but did not differ significantly among coal ash-compost mixes. For all media treatments, `Sierra' fruit size was inversely correlated with yield. Fruit from `Bluecrop' plants on coal ash-compost mixes ripened slightly earlier than on Berryland sand, but ripening date of `Sierra' did not vary significantly with soil treatment. The potential for employing these by-product mixes in small-scale commercial blueberry production will be discussed.

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Precocious varieties of highbush blueberry (Vaccinium corymbosum L.) may overcrop during the first few seasons in the fruiting field, adversely affecting plant establishment. Reducing or preventing bloom in the nursery and during establishment would be beneficial in preventing early cropping and reducing the risk of infection by pollenborne viruses. We investigated the efficacy of foliar applications of GA4+7 for suppressing flower bud initiation in blueberry. One-year-old rooted cuttings of ‘Bluecrop’ were obtained from a commercial nursery and established in 11-L pots at the Philip E. Marucci Blueberry and Cranberry Research Center, Chatsworth, N.J. Three separate experiments were conducted over three seasons with ‘Bluecrop’ (and ‘Duke’ in 2005) highbush blueberry where foliar applications of GA4+7 were made at concentrations ranging from 50 to 400 mg·L−1 a.i., with timing treatments ranging from 7 July to 15 Sept., with 10 replicate plants per treatment. Floral and vegetative buds were counted the following spring. In the first study, the greatest degree of flower bud suppression resulted from applications at 400 mg·L−1 repeated weekly from 7 July to 1 Sept. However, these treatments also reduced total vegetative bud number and plant height. In the two subsequent studies, the largest treatment effect resulted from three weekly applications in late August and early September, where flower bud numbers were suppressed by 70% to 85% for ‘Bluecrop’ and 95% for ‘Duke’ while total vegetative growth was unaffected.

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‘Montmorency’ tart cherry trees (Prunus cerasus L.) are grown commercially in the United States in low-density systems. Commercial tart cherry orchard design has not changed significantly over the past 50 years, but there is some variation from farm to farm in management strategies, including tree spacing, training, and pruning, and the resulting orchard production and turnover. Canopy dimensions and dynamics are important considerations for evaluating and improving orchard management strategies but are not well documented for tart cherry systems. Current orchard design and canopy management strategies were surveyed along a gradient of orchard age across five commercial farming operations in Utah. Trunk cross-sectional area and various canopy dimensions, including spread and volume, were quantified to capture tree size and canopy architecture. The survey indicated a surprising lack of deviation in orchard design in the region over the last several decades with higher variation among blocks within a farm than across farms. As a result, the survey revealed trends in tree growth and canopy structure across the range in orchard ages despite differences in management approaches of the surveyed farms. These trends were useful in illustrating canopy development and space fill. Tree age between 11 and 15 years after planting was determined to represent a transition between establishment and mature growth, where canopies filled available row space and began experiencing senescing canopy structure. Based on the distribution of ages captured in the survey, a significant number of orchards in Utah are at an age range of 11–15 years, perhaps contributing to superior yields per land area reported for the region. The confluence of space-fill and canopy development described in this study highlights a critical period for tart cherry orchard management at the transition of canopy establishment and maturity. These baseline dynamics will provide benchmarks for evaluating strategies for refining and improving orchard management systems for tart cherry in the Intermountain West region.

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The effects of NAA, BA, or Accel on CO2 assimilation of shoot leaves of mature bearing Redchief `Delicious' and `Empire' apple (Malus ×domestica Borkh.) trees were evaluated over two seasons. BA at 50 mg·L-1 did not significantly affect any of the gas-exchange parameters measured. NAA (15 mg·L-1) consistently suppressed CO2 assimilation rate (from ≈10% to 24% below that of the control). This suppression was NAA-concentration dependent, continued for >15 days after treatment, and was completely overcome in `Empire', but only partially or not at all in `Delicious' when BA was combined with NAA. These results are discussed in relation to fruit thinning and NAA-induced inhibition of fruit growth in spur-type `Delicious'. Chemical names used: 2-(1-napthyl) acetic acid (NAA); N-(phenyl)-1H-purine-6-amine (BA); BA + gibberellin A (GA)4+7 (Accel).

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The effect of temperature on uptake of C-labeled NAA was determined using detached apple leaves. Uptake by both adaxial and abaxial surfaces was measured at 15 and 35C over a 24-hotm period. Foliar absorption of NAA by the abaxial surface was greater than that by the adaxial surface. Absorption by the abaxial surface increased linearly (P < 0.001) with temperature over the range of 15 to 35C. These results are discussed in relation to fruit thinning. Chemical name used: 2-(1-naphthyl)acetic acid (NAA).

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Anticipating the phaseout of methyl bromide, the USDA-ARS small fruit breeding program at Beltsville, Md., discontinued soil fumigation in strawberry breeding and selection trials in the mid 1990s. To address resulting weed and pathogen pests, a modified or advanced matted row system was developed. This system uses matted row-type culture, established on raised beds with subsurface drip irrigation and organic mulch. The mulch is the residue of a killed cover crop that fixes some nitrogen and provides an economical, biodegradable mulch for suppressing weeds and reducing erosion. Since 1996, the small fruit breeding program has conducted replicated performance trials on both advanced matted row and a regional adaptation of annual hill plasticulture. Both of these systems were managed without methyl bromide fumigation or fungicide application. Data from these trials were used to compare advanced matted row and plasticulture for yield, fruit quality and harvest season. Yield for the two systems was genotype dependent, and the advanced matted row system had later production and slightly lower fruit quality.

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