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Ibukun T. Ayankojo, Kelly T. Morgan, Davie M. Kadyampakeni, and Guodong D. Liu

et al., 2012 ). As a result, the present study investigated the combination of different N and irrigation application rates under typical Florida tomato growing conditions to determine 1) the optimum N requirement for fresh-market tomato growth and

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Mary Jane Clark and Youbin Zheng

application rates for quality and growth of two nursery crops under temperate climate outdoor nursery production conditions in the Niagara region of Ontario, Canada, and 2) evaluate the nutrient status of the growing substrate following topdressing of two

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Douglas D. Archbold

177 ORAL SESSION 53 (Abstr. 376–383) Fruits: Growth and Development II

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Rizwan Maqbool, David Percival, Qamar Zaman, Tess Astatkie, Sina Adl, and Deborah Buszard

transition to reproductive phase) of complete N–P–K fertilization or genetic potential of the clones at our experimental site. P has been known to counteract the adverse effects (excessive vegetative growth) of excess N. The fertilizer N rate that correlated

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Mary Jane Clark and Youbin Zheng

rated relative to all other modules and based on plant growth, color, visual appeal, and perceived plant health. Vegetative coverage per module was visually estimated by comparing vegetation-covered with non-covered areas for both the proportion coverage

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Amy N. Wright, Stuart L. Warren, and Frank A. Blazich

Root growth is a critical factor in landscape establishment of container-grown woody ornamental species. Kalmia latifolia (mountain laurel) often does not survive transplanting from containers into the landscape. The objective of this experiment was to compare rate of root growth of mountain laurel to that of Ilex crenata `Compacta' (`Compacta' holly) and Oxydendrum arboreum (sourwood). Six-month-old tissue-cultured liners (substrate intact) of mountain laurel, 1-year-old rooted cutting liners (substrate intact) of `Compacta' holly (liner holly), 6-inch bare root seedling liners of sourwood, and 3-month-old bare-root rooted cuttings of `Compacta' holly were potted in containers in Turface™. Prior to potting, roots of all plants were dyed with a solution of 0.5% (w/v) methylene blue. Plants were greenhouse-grown. Destructive harvests were conducted every 2 to 3 weeks (six total harvests). Length, area, and dry weight of roots produced since the start of the experiment, leaf area, and dry weight of shoots were measured. Sourwood and liner holly had greater rate of increase in root length and root dry weight than mountain laurel and bare root holly. Rate of increase in root area was greatest for sourwood, followed by (in decreasing order) liner holly, mountain laurel, and bare-root holly. Increase in root length and root area per increase in leaf area was highest for liner holly, possibly indicating why this species routinely establishes successfully in the landscape. Increase in root dry weight per increase in shoot dry weight was lowest for mountain laurel. The slow rate of root growth of mountain laurel (compared to sourwood and liner holly) may suggest why this species often does not survive transplanting.

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Camille E. Esmel, Bielinski M. Santos, and James P. Gilreath

Nitrogen (N) is the most growth-limiting for vegetable production in sandy soils. In Florida, current recommendations for preplanting N applications (100 lb/acre of N) in `Crookneck' summer squash (Cucurbita pepo) differ from those used by the growers (>200 lb/acre). Therefore, two field studies were conducted in Ruskin and Balm, Fla., to examine the effect of 50, 100, 150, 200, 250, and 300 lb/acre of N on summer squash growth and yield. Variables collected during this study were plant vigor (0–10 scale, where 0 = dead plant) at 3 and 7 weeks after planting (WAP), petiole sap nitrate-nitrogen (NO3-N) at 4 and 8 WAS, and marketable yield starting on 4 WAS (13 and 10 harvests in Ruskin and Balm, respectively). In Ruskin, plant vigor increased linearly with N rates, whereas there was no significant N effect in Balm. No differences in petiole sap NO3-N were observed in either location. In Ruskin, there was a rapid marketable yield increase (§25%) between 50 and 100 lb/acre of N, followed by no change afterwards. In contrast, there was no yield response in Balm. In the latter location, no crop had been established in the previous 3 years, enabling the soil to maximize its organic N accumulation (>40 lb/acre organic-N), whereas in Ruskin the experimental location had been continuously planted during the last three seasons (§25 lb/acre organic-N). The data demonstrated that organic N is an important source of the nutrient to complement preplant applications in summer squash.

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E.W. Pavel and T.M. DeJong

Peach [Prunus persica (L.) Batsch] fruit thinning was used to reduce the competition for assimilates among peach fruits and to identify periods of source- and sink-limited growth during development. Individual fruit size, based on diameter or calculated dry matter accumulation, increased in trees with lower crop loads compared to fruits of unthinned trees in three peach cultivars. Relative growth rate analysis indicated that peach fruit growth was apparently limited by the assimilate supply (source-limited) or by its genetic growth potential (sink-limited) during specific growth periods. In stage I and at the beginning of stage III of the double-sigmoid growth curve, periods of source-limited growth occurred in the later-maturing cultivars Flamecrest and Cal Red. Peach fruit growth was apparently sink-limited during stage II of the growth curve when fruit relative growth rates were similar for the thinning treatments. Fruit growth in `Spring Lady', an early maturing cultivar, appeared to be primarily source-limited during the season. Although total fruit dry matter production was reduced by thinning, individual fruit dry weight on thinned trees was higher than that on trees with a heavy crop load. This typical thinning response was apparently caused by the differences in the amount of time that fruits grew under sink-vs. source-limited conditions with different crop loads. Final crop yield depended on fruit count per tree and on the available assimilate supply, and was affected by the individual fruit growth potential.

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D.G. Mortley, P.A. Loretan, C.K. Bonsi, W.A. Hill, and C.E. Morris

The effects of within-channel spacings (WCS; 13, 18, 25 cm) and between-channel spacings (BCS; 13, 25,38 cm) on yield and linear growth rate of sweetpotatoes [Ipomoea batalas (L.) Lam.] grown by use of the nutrient film technique (NFT) were evaluated. Storage root count, fresh and dry weights, and linear growth rate, expressed as root area, declined linearly in response to decreased BCS, while fresh and dry foliage weight decreased linearly and quadratically as spacing was reduced within the growth channels. Neither linear growth rate on a canopy area basis nor the edible biomass index was significantly affected by WCS or BCS.

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Bielinski M. Santos and Jose P. Morales-Payan

The effect of varying calcium (Ca), magnesium (Mg), boron (B), and molybdenum (Mo) rates on the growth of young `Cartagena Ombligua' papaya (Carica papaya) plants was studied in experiments conducted in the Dominican Republic. Rates of 0, 3, 6, 9, and 12 g Ca; 0, 0.85, 1.7, 2.55, and 3.4 g Mg; 0, 20, 40, 60, and 80 mg B; and 0, 0.05 0.1,0.15 and 0.2 mg Mo per plant were applied to the soil 20 days after transplanting. Ca did not stimulate plant growth, but instead was toxic at rates of 9-12 g per plant. Mg fertilization significantly stimulated root growth (Y = 2.35 + 0.48X, r 2 = 0.95), but not shoot growth. Mo applications decreased plant growth, whereas B enhanced overall plant growth (Y = 10.64 + 70.5X, r 2 = 0.96).