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Guihong Bi, Carolyn F. Scagel, and Richard Harkess

or quality ( Yeager et al., 1993 ). To optimize N fertilizer management in hydrangea production, knowledge of how rate and method of N fertilizer application influence plant performance is essential. Published literature on N use (optimum amount

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Thomas H. Yeager

Ilex vomitoria Ait. `Nana' root and-shoot growth increased as rate of fertilizer applied from a 6N-1P-3K solution increased from 0.5 to 2.5 g N/3-liter container during a 26-week experiment. Percentage of applied N, P, and Kin the plant and growth medium decreased as N applied increased. Dividing the fertilizer among one, two, or four applications per week resulted in similar use of applied N, P, and K. Shoot dry weights for the 0.5 g N/container treatment were less than for the Osmocote (18N-2.6P-10K) treatment (2.5 g N/container), but the percentage of applied N, P, and K in the plant and growth medium (55%, 42%, and 75%, respectively) was greater than for the Osmocote treatment (31%, 15%, and 27%, respectively).

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G. Stephen Crnko, Edward W. Bush, and Allen D. Owings

A study was initiated to determine the effects of fall fertilization, specifically N application rate and additions of supplemental K on the production of woody ornamental shrub species. The influence of two slow-release sources of K (4- and 8-month) in the form of K2SO4, three K application rates (0, 1, 2 lb/yd3), and four incorporated application rates of N (0, 1, 2, and 3 lb/yd3) from Osmocote Plus+ 15-9-11 were evaluated on the growth of `Fisher Pink' Indian azalea, glossy abelia, and `Tuscarora' crape myrtle. Growth of `Fisher Pink' azalea, as determined by shoot height and shoot width, increased as N rate increased from 1 to 3 lb/yd3 when compared to the control. The resulting growth index improved at the 2 and 3 lb/yd3 N rate when compared to the 0 and 1 lb/yd3 N rates. Height and width of glossy abelia at the 1 lb N rate with or without supplemental K applications increased when compared to some glossy abelia at the 3 lb N rate (primarily those with supplemental K). Glossy abelia at the 2 lb/yd3 N rate with 2 lb/yd3 N from 4-month 0-0-46 had significantly greater shoot dry weight when compared to the 3 lb/yd3 N rate with 2 lb/yd3 N from 8-month 0-0-46. The 1 to 3 lb/yd3 N application rate had more of a response on growth index, visual quality, and visual color on `Tuscarora' crape myrtle as compared to the 0 lb/yd3 N rate. In this study, the potential influence of supplemental K applications on plant growth was mostly evident for glossy abelia at the 2 lb/yd3 N rate and was not evident on azalea or crape myrtle.

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Robert Wiedenfeld

Onion production requires N fertilization, yet use efficiency of applied N is low. Improvements may be possible with a better understanding of plant growth and nutrient requirements over time. Onion growth and nutrient uptake was extremely slow during the winter months following planting, then increased substantially in the spring. Onion leaf N concentrations declined with age, while bulb N concentrations fluctuated with growing conditions but showed no longterm trend. Responses to N application were due primarily to timing and less to rate applied. Nitrogen uptake increased in some cases very quickly following N application, and in other situations was still evident after 6½ months. Yield increases, however, occurred only for preplant and winter fertilizer applications, not for spring application. Yield responses to both timing and rate varied by cultivar, with the later maturing cultivar doing best at the highest rate of preplant and the higher 2 rates of the winter applied N fertilizer.

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Anas D. Susila and Sal J. Locascio

Tomato (Lycopersicon esculentum L.) was grown with polyethylene mulch and drip irrigation on a Millhopper fine sandy soil testing very high in P and low in organic matter during two season to evaluate the effect of S source, rate, and application methods on plant growth and yield of fruit. S rates of 34 and 68 kg S/ha were applied preplant (broadcast in the bed), by drip (10 weekly drip application), and by split applications (40% preplant and 60% drip). In split applications, S sources evaluated were ammonium sulfate and ammonium thiosulfate. Plant height was increased with S application from 0 to 68 kg S/ha in both studies. However, response on plant dry weight only occurred in Spring 1999. Total marketable yield was 17.9 tons/ha with 0 kg S/ha and was increased quadraticaly to 48.1 tons/ha with application of 68 kg S/ha in Spring 1999, but no response to S was obtained in the Spring 1998 study. Measured variable were not affected by S source and methods of application. Increasing S application from 0 to 68 kg S/ha reduced leaf and plant tissue P concentration 14% and 12% at mid season and 26% and 25% at late-season sampling, respectively. Application of 68 kg S/ha reduced soil pH ≈0.3 unit at the end of the season in both studies.

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Agnes M.S. Nyomora, Patrick H. Brown, and Bill Krueger

Previous studies with tree species have demonstrated that foliar boron (B) promotes flowering, fruit set, and yield. However, for most species the optimum time for foliar B application has not been determined. This investigation was undertaken to study the effects of time and rate of B application on almond [Prunus dulcis (Mill D.A. Webb)] tissue B concentration, fruit set, and yield. Solubor (Na2B8O13.4H2O), a commercial product containing 20.5% B, was applied with a handgun sprayer either in September (3 weeks postharvest), December (dormancy), or February (budbreak) at rates of 0, 0.8, and 1.7 kg·ha-1 B to almond cv. Butte at one site (Parlier, Fresno County, Calif.), and of 0, 0.8, 1.25, 1.7, and 2.1 kg·ha-1 B on the same cultivar in August, September, or February at a second site (Orland, Glenn County, Calif.) using Borosol, a polyboronated commercial product containing 10% B. At site 1, September application was more effective in increasing tissue B concentration, fruit set, and yield than were December or February applications. The optimal rate was 0.8 to 1.7 kg·ha-1 B when applied in September. At site 2, application in 1996 and 1997 increased tissue B concentration almost linearly, especially when applied in August and February. Application at the highest rate (2.1 kg·ha-1 B) in September produced the greatest final fruit set and yield in 1996. February applications increased initial fruit set at both sites but were less effective than September applications in increasing yield. Application of B did not affect any yield variable in 1997. These results suggest that B should be applied immediately postharvest (September) for optimal effect on tissue B concentration, fruit set, and yield in almond.

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T.J. Tworkoski and R.S. Young

Triclopyr was applied once or twice in consecutive years to Virginia creeper [Parthenocissus quinquefolia (L.) Planch.] that was growing along the ground beneath the peach [Prunus persica (L.) Batsch.] tree canopy. All rate (0 to 1.1 kg·ha-1) and month combinations controlled Virginia creeper during the season of application. A single application of triclopyr at 1.1 kg·ha-1 was insufficient for control beyond 1 year. Satisfactory control of Virginia creeper was obtained with two applications of triclopyr at 1.1 kg·ha-1 made in either August or September. Chemical name used: [(3,5,6-trichloro-2-pyridinyl)oxy]acetic acid (triclopyr).

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Jonathan R. Schultheis and Dennis E. Adams

Boron has been used to overcome the disorder blister in varieties such as `Jewel'. `Hernandez' is an attractive, good-yielding variety with uniform shape that will consistently pack out at 80% to 90%. Over time in storage, however, roots develop blister-like symptoms, rendering roots unmarketable for fresh market. Our objective was to evaluate the effect of different B rates and application times on the yield and quality of `Hernandez' roots. Rates were varied up to 2.24 kg actual B/ha 6 days after planting, while various soil and foliar application times (6, 34, and 69 days after planting) were evaluated at 1.12 kg·ha–1. In 1994, three row plots were arranged in a randomized complete block design and replicated four times. Planting was on a deep sand to maximize the effect of the B carrier Solubor. Roots were harvested, graded, and weighed 120 days after planting and storage roots evaluated for blister-like symptoms in Mar. 1995. No significant differences in yield were attributed to B rate or application method. Blister-like symptoms were more severe when no B was applied; however, application of B did not eliminate symptoms, as most roots had the blister-like appearance. Boron application did not solve the problem, but symptoms were less apparent when some B was applied.

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Larry R. Parsons, T. Adair Wheaton, and William S. Castle

Citrus trees in an experimental planting responded well to high application rates of reclaimed water. Irrigation treatments included annual applications of 400 mm of well water and 400, 1250, and 2500 mm of reclaimed water. The effects of these irrigation treatments on two citrus cultivars (`Hamlin' orange and `Orlando' tangelo) combined with four rootstocks were compared. Growth and fruit production were better at the higher irrigation rates. The concentration of soluble solids in juice was diluted at the highest irrigation rate, but total soluble solids per hectare increased due to the greater fruit production. Average soluble solids/ha production was >15% higher at the 2500-mm rate than the 400-mm reclaimed water rate. While fruit soluble solids were usually lowered by higher irrigation, the reduction in fruit soluble solids observed on three of the rootstocks did not occur in trees on Carrizo citrange. Trees on Cleopatra mandarin grew similarly at the different irrigation rates, but canopy volume of trees on Swingle citrumelo was significantly smaller at the 400 mm rate than at the 2500 mm rate. Fruit peel color score was lower but juice color score was higher at the highest irrigation rate. Weed pressure increased with increasing irrigation rate, but was controllable. Both juice and fruit soluble solids were higher on Swingle citrumelo and lower on Cleopatra mandarin rootstock. Total soluble solids/ha, solids/acid ratio, and juice color were higher on Swingle rootstock. Reclaimed water, once believed to be a disposal problem in Florida, can be an acceptable source of irrigation water for citrus on well drained soils at rates up to twice the annual rainfall.

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Robert H. Stamps

One of the most difficult times to balance crop nitrogen (N) requirements with concerns about nitrate-N leaching occurs during crop establishment, when root systems are poorly developed and not widely distributed in the growing medium. This dilemma can be exacerbated when producing a slow-growing plant such as leatherleaf fern (Rumohra adiantiformis [Forst.] Ching) on sandy soils in shadehouses in areas with significant rainfall. Rhizomes were planted in 36 drainage lysimeters containing Tavares fine sand located in a shadehouse. Nitrogen fertilizer was applied at nine rates using liquid and/or controlled-release fertilizer. Nitrogen application rates were varied as the rhizomes became established and spread into unplanted areas of the lysimeters. Irrigation and rainfall were monitored and the amount of water not lost to evapotranspiration was determined. Nitrogen (ammoniacal, nitrate/nitrite, total Kjeldahl) concentrations in leachate collected below the rootzone were determined. Stipe sap nitrate and frond total Kjeldahl nitrogen (TKN) were determined to try to develop a production monitoring technique. Initially, only leachate samples from controlled-release fertilizer plots treated at 21 and 42 kg of N/ha per year and liquid fertilizer at 28 kg of N/ha per year were consistently below the maximum contamination level (MCL) of 10 mg·L–1. As the fern became established, leachate nitrate/nitrite-N concentrations from higher N application rate treatments also remained below the MCL. Leachate N concentrations decreased as rainfall increased. Fern growth increased with increasing N application rate. Stipe sap nitrate-N and frond TKN concentrations were not well-correlated during establishment.