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Luz M. Reyes, Douglas C. Sanders, and Wayne G. Buhler

). Various types of slow-release fertilizers may extend the availability of nutrients, especially N, to the plant ( Maynard and Lorenz, 1979 ) and reduce N leaching losses from soil ( Wang and Alva, 1996 ). Research has been conducted with sulfur-coated urea

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L. Carolina Medina, Jerry B. Sartain, and Thomas A. Obreza

Nutrient use efficiency, particularly for nitrogen (N) fertilizer, is still low despite significant improvements in crop production over the last few decades. Development of slow-release fertilizer (SRF) evolved as a potential way to enhance

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William Terry Kelley

Despite some advantages, adoption of slow-release fertilizers in vegetables has been slow primarily due to cost. In crops fertilized with ground equipment, growers can make fewer trips through the field and assure fertilizer is present when conditions prevent application. With drip irrigation, some materials are difficult to inject, however, Nitamin is a new injectable liquid produced by Georgia Pacific. Thus, with plasticulture, growers can inject less frequently and potentially use lower rates. Granular and liquid formulations of slow-release fertilizer were tested on onions (Winter 2003–04), cabbage (Winter 2003–04) and pepper (Spring 2004) in Georgia. Combinations of traditional fertilizer with slow-release formulations and various rates of slow-release fertilizer alone were compared to a standard fertilizer program on these crops in separate experiments. The slow-release contains only N. So, other nutrients were held constant. Otherwise normal cultural practices were employed. Crops were harvested at maturity and data collected on yield and quality. In cabbage, with at least 50% of the standard N rate using the slow-release fertilizer, yields were comparable to the standard. Results on onions were similar with N rates of at least 75% of the standard for the liquid material; the granular formulation did not perform well. Split applications of slow-release fertilizer and combinations with standard fertilizer worked well for cabbage, but not for onions. Results on pepper, although inconclusive, indicated it was possible to get comparable yields at lower N rates with the slow-release material. Based on these results, lower N rates are possible on cabbage and onions with slow-release fertilizers which may make them economically feasible while providing application advantages to growers.

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Bert T. Swanson, James B. Calkins, Daniel G. Krueger, and Theresa L. Stockdale

Media fertility is a critical factor in the successful production of container grown plants. Fertility treatments including fertigation and slow-release fertilizers (topdressed and incorporated) were compared. Fertility treatments were studied over a two-year period on a variety of deciduous and evergreen plant materials. Plant growth was quantified based on height, volume, branching, and quality. Soil fertility levels based on leachates were followed during the study. Nutrient release for incorporated fertilizers tested was variable although less so than when the same fertilizers were topdressed. Fertility treatment effects were species-dependent. Several incorporated, slow-release fertilizers, especially those high in nitrogen (Sierra 17-6-10, Sierra High N 24-4-6, Woodace Briquettes 23-2-0, Woodace 21-4-10), show promise for use in two-year container production systems.

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Edward Bush, Jeff Kuehny, and Patricia Branch

Three slow-release fertilizer formulations (Osmocote 14–14–14, 18–6–12, and Nutricote 17–6–10) at three rates (1, 2, and 3 lb/yd3) were incorporated into 4 pine bark: 1 sand (by volume) media filling 1-gal nursery containers. Additional treatments included slow-release fertilizer formulations at 1 lb/yd3 fertigated with 100 ppm N 20–10–20 fertilizer. As fertilizer rates increased, vegetative height, width, and dry-weight accumulation generally increased for both pinched and no-pinch mum crops. Fertigated pinch and no-pinch mums were the largest plants with the greatest dry-weight accumulation for each fertilizer formulation. The high rate for all slow-release fertilizers produced the greatest vegetative growth for nonfertigated treatments. This research suggest that higher rates for incorporated slow-release fertilizers and/or fertigation are required to produce maximum vegetative growth.

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Wendy Britton, E.J. Holcomb, and David J. Beattie

Four rates of two slow-release fertilizers were tested for optimum growth of five hosta cultivars: Hosta sieboldiana `Elegans', Hosta plantaginea `Aphrodite', Hosta `Jade Scepter', Hosta `Hadspen Blue', and Hosta `Francee'. Tissue-cultured hostas from 2.5-cm plugs were planted in 6-inch (15-cm) pots filled with a commercial soilless medium, and the slow-release fertilizer was dibbled into the medium at 0, 3, 6, or 12 g/pot. The plants were maintained for 4 months. Root and shoot fresh and dry weights were recorded at the end of the experiment. In addition, foliar nutrient analysis was conducted on `Aphrodite', `Francee', and `Jade Sceptor'. Overall, hostas grew best when the medium was amended with 3 g of either Osmocote 14N-6P-11.5K or Sierrablen 17N-6P-12K slow-release fertilizer.

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James B. Calkins and Bert T. Swanson

Media fertility, nutrient availability, and subsequently plant nutrition are critical factors that can be modified by growers to produce quality container-grown plants. The trend in container fertility has been toward incorporation of slow-release fertilizers; however, fertility release curves are variable and fertilizer longevity for many fertilizers is limited. Seventeen slow-release fertilizers were compared for longevity and plant performance over a 2-year production cycle using deciduous and evergreen plant materials. Plant growth was quantified based on height, volume, branching, dry weight, and quality. Soil fertility levels based on leachates were followed. Nutrient release for the incorporated fertilizers evaluated was variable. Fertility treatment effects were species-dependent. Several incorporated, slow-release fertilizers, especially those high in nitrogen and having extended release curves, including Nutricote 20–7–10, Scotts Experimental 24–6–10 and 26–6–11, Scotts Prokote Plus 20–3–10, Sierra 17–6–10, Sierra High N 24–4–6, Sierra Experimental 24–4–8, Woodace 21–4–10, Woodace 23–7–12, and Woodace Briquettes 23–2–0, show promise for use in 2-year container production systems.

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Joseph Eakes and John W. Olive

Five 12- to 14- month slow release fertilizers (Osmocote 17-7-12, Sierra 16-6-10, High-N 24-4-7, Sierrablend 17-7-10, and Nutricote 16-10-10 Type 360) were incorporated into a 3:1 pine bark: peat moss potting medium at one of 4 rates (0.9, 1.2, 1.5, and 1.8 kg N/m3). Plant growth of 3 azale a species, `Coral Bells' (Kurume), `Formosa' (Southern Indica), and `Pink Gumpo' (Satsuki), and monthly medium solution electrical conductivity (EC) were determined. Growth indices 180 days after applying fertilizer were greatest for plants receiving the Sierrablend and Osmocote fertilizers regardless of azalea species. Plant growth indices increased as N rate increased for the 3 azaleas, regardless of the fertilizer product. The highest media solution EC readings occurred during the first 90 days after fertilizer application for all fertilizer treatments and declined thereafter.

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Shaun R. Broderick and Williams B. Evans

effectiveness of these biosolids as a fertilizer and soil amendment and compare their performance with conventional and slow-release fertilizers. Materials and methods Grade A, EQ biosolids were obtained from the City of Clinton (Mississippi) Department of

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Kimberly Klock-Moore

The objective of this experiment was to compare the growth of impatiens `Accent Orange' in substrates containing compost made from biosolids and yard trimmings with four slow-release fertilizer application rates. Plugs of impatiens were transplanted into 400-ml pots filled with 100% compost as a stand-alone substrate or with 60%, 30%, or 0% compost combined with control substrate components. Six days after transplanting, all plants were top-dressed with 0.5, 1, 2, or 4 g of Nutricote 13N-5.7P-10.8K (type 180) per pot. Shoot dry mass increased as the percentage of compost in the substrate increased from 0% to 100%. Shoot dry mass also increased as the fertilizer application rate increased from 0.5 to 4 g per pot. Plants grown in 30% and 60% compost with 0.5 g of fertilizer were similar in size to plants grown in 0% compost with 4 g of fertilizer per pot. Plants grown in 100% compost at all of the fertilizer rates were larger than all other plants in this study.