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K.M. Ryan, J.H. Edwards, C.H. Gilliam and G.J. Keever

Blue color development in Hydrangea macrophylla is usually accomplished by applying Al as an alum drench. Drenches are applied during forcing 10–14 days after transplanting at a rate of 17,500 mg·L-1. Cultivars Blue Wave and Nikko Blue were used to evaluate if the Al contained in waste paper can provide the necessary Al for blue flower development. Two waste paper forms, pelletized and crumble, were used as surface mulches and as media amendments. The amendments were incorporated into the media at transplanting and mulches were applied either at transplanting or 28 days later. Alum drenching was initiated at transplanting as a control. Leachates were collected weekly using the VTEM. Total Al, electrical conductivity, and pH were determined on all samples. All waste paper treatments resulted in pink flowers in both cultivars. Leachate pH, from plants in this test, was >6.5. Aluminum concentration was greater than the 15 mg·L-1 Al needed for blue color development in flowers, but Al concentration decreased with time. Control of pH at the waste paper surface and in the media is critical for increasing the availability of labile Al for uptake by hydrangea.

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C.K. Crossan, C.H. Gilliam, G.J. Keever and D.J. Eakes

Herbicide-blended and coated fertilizers were evaluated for prostrate spurge control in containers. Ronstar 2G or Pennant 5G was blended with Nursery Special 12-6-6 fertilizer and Ronstar 50WP or Pennant 7.8E was sprayed on the fertilizer (coated). Ronstar 2G-blended fertilizer and Ronstar. 50WP-coated fertilizer provided weed control at the 4, 8, and 16 lb ai/A rates similiar to broadcast (2G) or sprayed (50WP) herbicide applied at the label rate (4 lb ai/A). Ronstar provided better prostrate spurge weed control than Pennant. Formulation had no affect on weed control when comparing blended or coated fertilizer. Herbicide-blended and coated fertilizers provided effective prostrate spurge contol in containers.

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J.O. Glenn, C.H. Gilliam, J.H. Edwards, G.J. Keever, J. Olive and P.R. Knight

Recycled paper pellets in the bottom of containers were evaluated for retention of N from container leachate. `Formosa' azalea were transplanted on 15 Apr. in 2.8-L containers in a pine bark/peat substrate (3:1; v/v). Treatments included paper (0 or 2.5 cm depth) in the bottom of containers and two rates of Osmocote 18–6–12 (0.68 kg or 1.36 kg N/yd3). Immediately after transplanting, plants were topdressed with 3.2 g of 12–4–6 fertilizer. Data collected included leachate samples every 2 weeks for NO3-N and NH4-N levels and destructive sampling every 4 weeks for shoot dry weight, foliar N, and total paper N. Nitrate-N and NH4-N leachate concentrations were reduced with the 0.68 kg N/yd3 fertilizer rate and with paper. For example, 28 days after planting (DAP) NO3-N leachate concentrations were reduced 36% with the 0.68 kg N/yd3 fertilizer rate and 46% with paper in the bottom of containers. NH4-N in the leachates was reduced 53% with the 0.68 kg N/yd3 fertilizer rate and 59% with paper. Azalea shoot dry weight was not affected by paper or fertilizer rate up to 112 DAP; however, as the study progressed, plants with paper in the bottom of containers grew larger than plants in no paper treatments (29% at 168 DAP, 31% at 196 DAP). Total N absorbed by paper was not affected by fertilizer rate, and peaked at 168 DAP [980 (0.68 kg N/yd3) to 1066 (1.36 kg N/yd3) mg per container, or 41% – 28% of applied N], after which it began to decline. This decline in paper N was associated with greater growth of azalea with paper.

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J.S. Glenn, C.H. Gilliam, J.H. Edwards, G.J. Keever, P.R. Knight and J.W. Olive

Two experiments were conducted to evaluate recycled newspaper products as nutrient filters in the bottom of containers. In Expt. 1 with poinsettia, Euphorbia pulcherrima Willd. ex Klotzsch `Glory', three paper products were evaluated: ground paper, paper crumble, and paper pellets; each placed 2 or 3 cm deep in the bottom of containers, so that drainage holes were covered. Leachate samples were collected at the first irrigation after each liquid fertilization. Nitrate (NO3 --N) and ammonium (NH4 +-N) leachate concentrations were reduced up to 84% with recycled paper pellets, compared to the control (no paper). Recycled paper retained up to 732 mg of nitrogen (N) per container (paper pellets 3 cm deep). Shoot dry weight was reduced with paper pellets but was not affected by ground paper or paper crumble. In Expt. 2, `Freedom Red' poinsettias were grown with either single weekly applications of 500 mg·L-1 N from Peter's 20N-4.3P-16.6K, or 200 mg·L-1 N at each irrigation (2 or 3 times a week, as needed). Recycled paper treatments included paper crumble or paper pellets placed 2.5 cm deep in the bottom of containers, and a control without paper. Leachate NO3 --N and NH4 +-N concentrations were reduced up to 100% and 94%, respectively, 6 days after planting (DAP), and up to 57% and 50%, respectively, 25 DAP with paper crumble compared to nonpaper control. Paper pellets in the bottom of containers retained up to 776 mg N per container. Poinsettia shoot dry weight was lowest with paper pellets in the bottom of containers and continuous fertilization.

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K. R. Keel, C. H. Gilliam, G. R. Wehtje, T. L. Grey, G. J. Keever and D. J. Eakes

Several experiments were conducted to determine release rates of five oxadiazon-coated fertilizers. Five fertilizers and 4-mm glass beads (nonabsorbent control) were coated with 14C-oxadiazon + formulated oxadiazon, then placed in a separatory funnel and leached with 20 ml of water for 14 days. 14C-oxadiazon was quantified by use of liquid scintillation spectrometry. For glass beads, Nutricote, Meister, and Osmocote, 70% to 80% of the 14C-oxadiazon was recovered in the first two leaching events. Oxadiazon leached from Polyon was 47% during the first two events and remaining oxadiazon was slowly released over the next 12 leaching events. 14C-oxadiazon from the other fertilizers over the last 12 days of leaching was less than that recovered from Polyon. Evaluation of the total surface area of a 50-g sample revealed Polyon had the greatest total surface area of the five fertilizers. Scanning electron micrographs before and after leachingindicated potential erosion of the Polyon surface compared to little or no change in the surfaces of the other fertilizers.

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D.C. Fare, C.H. Gilliam, G.J. Keever and R.B. Reed

The effects of overhead pulse irrigation versus conventional overhead irrigation on growth of Ageratum houstonianum `Blue Puff' in 2 media, container leachate volumes and leachate NO3-N and NH4-N levels were evaluated. Container leachate volumes, and NO3-N and NH4-N levels were higher with pinebark:sand medium. Container leachate volumes tended to be lower with pulse irrigation compared to conventional irrigation. Shoot dry weights of plants grown in pinebark:peat were greater under conventional irrigation compared to pulse irrigation; however, growth indices, flower number, and NO3-N and NH4-N levels were not affected by irrigation method in either medium.

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Jeff L. Sibley, D. Joseph Eakes, Charles H. Gilliam, Gary J. Keever, William A. Dozier Jr. and David G. Himelrick

Twelve red maple selections in an existing field trial were evaluated for leaf chlorophyll content with a SPAD-502 chlorophyll meter, total foliar N concentration with a LECO CHN analyzer, and total foliar chlorophyll content (CHL) by N,N-dimethylformamide extraction. Selections included Acer rubrum L. `Autumn Flame', `Fairview Flame', `Franksred' (Red Sunset™), `Karpick', `Northwood', `October Glory', `Redskin', `Schlesingeri', and `Tilford', and A. ×freemanii E. Murray `AutumnBlaze' (`Jeffersred'), `Morgan' (`Indian Summer'), and `Scarsen' (Scarlet Sentinel™). `Franksred' and `Northwood' had the highest monthly SPAD-502 values in 1993 and 1994. Lowest SPAD-502 values were on `Redskin' and `Autumn Blaze' each year. Foliar N concentration ranged from 2.62% for `Autumn Flame' to 2.01% for Redskin. CHL levels on a fresh-weight basis ranged from 5.38 mg·g–1 for `Fairview Flame' to 3.94 mg·g–1 for `October Glory'. SPAD-502 and extractable CHL values were correlated (r = 0.45; P ≤ 0.001); however, the correlation (r = 0.15; P ≤ 0.38) between SPAD-502 values and total foliar N concentration was nonsignificant.