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Manuel Martínez-Estévez, Nancy Ruiz-Lau, Rita Elena May-Uluac, Adolfo Guzmán-Antonio, Fausto Quintal-Tun, and Ramón Pacheco-Arjona

Dynamics and distribution of K, Ca, Mg, P, and Na were studied in leaves of three cultivars of habanero pepper (Capsicum chinense Jacq.) at the time of transplanting and 8 and 14 weeks afterward. Most nutrients analyzed were mobilized from younger to mature leaves, except for P, which occurred in the opposite direction, probably due to its role in the synthesis of nucleic acids, which is more active in young tissues. Information about mineral distribution in leaves during the first 14 weeks after transplantation could be used to indicate plant nutritional status and fertilizer requirements.

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Franz J. A. Niederholzer and R. Scott Johnson

Urea foliar sprays may be a more efficient and environmentally sound alternative to soil applied fertilizer N in the postharvest period in tree crop production in California. While tree crop sulfur (S) status can interact with tree N status to affect growth, we know of no study assessing tree crop leaf N and S dynamics following fall (postharvest) foliar urea applications. We conducted a field study to measure temporal dynamics of leaf N and leaf S (% dry weight basis) following postharvest urea sprays on prune (Prunusdomestica) and almond (Prunus dulcis). June-budded nursery stock prune (`French' on Myro 29C) and almond (`Price' on Lovell) trees were sprayed to dripping with 6.5% (w/w) and 10% (w/w) standard urea solutions, respectively. Prunes were sprayed on 1 Oct. 2003 and almonds on 18 Nov. 2003. Leaf samples were taken over a 3-week (almond) or 8-week (prune) period, beginning just before treatment. Foliar urea sprays significantly increased prune (23%) and almond (14%) leaf N compared to untreated control within 8 days of application. This affect was transient, as there were no differences in leaf N concentrations between treated and untreated trees at final leaf sampling. Urea sprays did not affect almond leaf S concentration relative to untreated trees. Prune leaf S was significantly reduced compared to untreated trees 8 days after treatment, but only on that sampling date. Remobilization of S from the leaves of control trees of either species was not apparent.

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Juan A. Argüello, Alicia Ledesma, Selva B. Núñez, Carlos H. Rodríguez, and María del C. Díaz Goldfarb

The objectives of this work were to a) determine vermicompost effect on bulbification dynamics in terms of garlic (Allium sativum L.) bulb dry weight and sucrose metabolism and b) evaluate the impact of vermicompost on garlic bulb yield and quality. The treatments were soil (control) and 1 soil: 1 vermicompost (by volume). The use of vermicompost as a substrate caused early bulbing (18 to 20 days) and lengthened bulb filling period. Bulb filling period corresponded to an increase in the total soluble carbohydrates and a later modification in nonstructural carbohydrate distribution patterns regarding fructan (scorodose) metabolism. The vermicompost treatment increased scorodose accumulation, which was directly related to the harvest index, resulting in greater yield and bulb quality. Bulb quality was not modified in terms of bulb pungency and soluble solids content by the use of vermicompost.

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Regina L. Reickenberg and Marvin P. Pritts

The dynamics of nutrient uptake from foliar applied 15N-urea and Rb (a K analog) were quantified in red raspberries. Both N and Rb in an aqueous solution were absorbed rapidly into the leaf and transported throughout the plant. In the greenhouse, about half of the urea and a third of the Rb were absorbed within 32 hours of application. The addition of a surfactant to the foliar solution reduced uptake, while solution pH, time of application and leaf age had little effect. The lower leaf surface exhibited a faster rate of absorption than the upper surface, but the difference was not large. In the field, some foliar N appeared to have been washed off leaves and taken up by the root system; however, none of the foliar applications affected plant growth. We conclude that significant uptake of foliar applied N and K occurs in raspberry, but the absolute amount delivered through a single foliar application is small. The percentage of total plant nutrient supplied through a foliar application is reduced to < 5% over time as the plant grows, so multiple applications would be required to maintain levels significantly higher than would exist through root uptake alone.

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Raul I. Cabrera, Richard Y. Evans, and J.L. Paul

N uptake by greenhouse roses is out of phase with flower shoot elongation, such that N uptake is highest when shoots are not growing and lowest when shoots are elongating rapidly. Isotopically labelled 15N fertilizer was supplied at different stages of one flowering cycle to `Royalty' rose plants growing in a static nutrient solution system to study the partitioning of recently-absorbed N and the dynamics of N partitioning. After a two-day exposure, whole plants were harvested, separated into old and new leaves, stems, and roots, and analyzed for total N and 15N enrichment. During rapid shoot elongation, N uptake by roots supplied 16 to 36% of shoot N demand. The remaining N came from other organs, particularly old stems and leaves. The increased N uptake later in the flowering cycle was sufficient to meet shoot N demand and replenish the N supply in old foliage and woody tissues. These organs continued to accumulate N until the subsequent bud break, when this N became available for the next cycle of flowering shoot growth.

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Conny W. Hansen and Jonathan Lynch

Whole-plant biomass accumulation, P dynamics, and root-shoot interactions during transition from vegetative to reproductive growth of `Coral Charm' chrysanthemum (Dendranthema ×grandiflorum Ramat.) (Zander, 1993) were investigated over a range of P concentrations considered to be deficient (1 μm), adequate (100 μm), and high (5 mm). In nondeficient plants, transition from vegetative to reproductive growth resulted in reduced relative growth rate and root and shoot biomass accumulation. Reproductive plants showed a higher commitment of the whole plant to the production of developing flowers than to leaves and roots, whereas, in vegetative plants, the highest component production rate was in leaves. This indicates changes in the source-sink relationships during transition from vegetative growth making developing flowers stronger sinks for photoassimilates than roots. Phosphorus allocated to developing flowers was predominantly lost from leaves. Phosphorus-deficient plants showed characteristic P-deficiency symptoms and favored root growth over shoot growth regardless of growth stage. Phosphorus availability in nondeficient plants affected root growth more than shoot growth. No substantial differences in shoot biomass production, relative growth rate, and CO2 assimilation rates were observed in adequate-P and high-P plants. However, the root component production rate, root to shoot ratio, root length ratio, specific root length, specific root area, root mass to leaf area ratio, and root respiration increased in adequate-P plants compared with high-P plants, which indicates that high root activity was maintained without affecting shoot biomass in buffered P conditions. Our results suggest that the high P concentrations used in many horticultural systems may have no benefit in terms of shoot growth and may actually be detrimental to root growth.

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Mathieu Ngouajio*, Mary K. Hausbeck, Daniel M. Sullen, Mohan Selvaraj, and Kevin Charles

Michigan is the national leader for pickling cucumber production. However, over the last few years growers have witnessed a considerable decline in marketable yield, mainly attributed to fruit rot caused by Phytophthora capsici. Phytophtora develops rapidly under high relative humidity, a situation commonly found with narrow rows. Growers are interested in using wider rows but would like to know if there are any associated yield reductions. This study was conducted in 2003 to measure the effects of cucumber plant populations on canopy dynamics and fruit yield. Cucumbers were grown with between-row spacing of 30.5, 45.7, 61.0, and 76.2 cm, and in-row spacing of 10.2, 12.7, and 15.2 cm. A split-plot design with four replications was used. Row spacing was the main plot factor, and in-row spacing the subplot factor. Soil covered by plant canopy was monitored throughout the growing season using digital image analysis techniques. At harvest, the number of fruits per plant and marketable yield for the different grades were measured. Cucumber canopy remained open during the major part of the growing season when wide rows (61.0 and 76.2 cm) were used. The number of fruits per plant increased from an average of 1.5 fruits at 30.5 cm to 2.0 fruits per plant at 61.0 cm. Further widening of row spacing to 76.2 cm slightly reduced the number of fruits per plant. Therefore, the optimum row spacing would be 61.0 cm if the number of fruits per plant was the only parameter being measured. Cucumber marketable yield was similar with 30.5, 45.7, and 61.0 cm spacing between the rows. With 76.2-cm rows, yield reduced slightly. These results suggest that cucumber plant density can be reduced substantial with limited yield penalty.

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Christina Wells and Desmond Layne

We are using a minirhizotron camera system to observe fine root dynamics beneath irrigated and nonirrigated peach trees. Our long term goals are: 1) to relate the timing of fine root production to tree phenology, soil water content, and soil temperature; and 2) to determine how fine root architecture and demography differ between trees with and without supplemental irrigation. In early 2002, minirhizotrons were constructed and installed beneath each of 72 open-center, 4-year-old `Redglobe' peach trees at the Musser Fruit Research Farm near Clemson University. Beginning in May 2002, videotaped images from each minirhizotron were collected at 2-week intervals; notes on tree phenology were also recorded biweekly. Videotapes were digitized in the lab, and information on root length, diameter, appearance and longevity was extracted from the images. Soil temperature and volumetric water content were measured in the orchard throughout the growing season. In the 2 years following minirhizotron installation, irrigated trees allocated a significantly greater percentage of their fine root length to the upper soil layers and exhibited less root branching than nonirrigated trees. Fine roots produced by irrigated trees lived significantly longer: irrigated trees had a median root life span of 165 days, while nonirrigated trees had a median root life span of only 115 days (P< 0.001; proportional hazards regression). Fine roots from irrigated trees remained in the physiologically active “white” state for an average of 10 days longer than roots from nonirrigated trees (P< 0.001). Data from 2002–03 indicate that the trees produce new root flushes at least three times during the year, with a significant flush occurring immediately after harvest.

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Laura L. Van Eerd and Kelsey A. O'Reilly

efficiency (NUE). This is particularly true in cucurbit crops, in which plant N uptake and soil N dynamics have been quantified in squash ( Mohammad, 2004 ), but differences in crop species, climate, soil characteristics, and crop management may significantly

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Thomas G. Bottoms, Timothy K. Hartz, Michael D. Cahn, and Barry F. Farrara

applied to seven California strawberry fields ranged from underirrigation to a leaching fraction of 28%. The primary objective of this study was to document plant and soil N dynamics in annual strawberry production under the environmental conditions and