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Ka Yeon Jeong and James E. Altland

Bagged potting mixes can be stored for weeks or months before being used by consumers. Some bagged potting mixes are amended with controlled release fertilizers (CRFs). The objective of this research was to determine how initial substrate moisture content and storage temperature affect the chemical properties of bagged potting mix with CRF incorporated and stored for up to 180 days. The base substrate composed of 60 sphagnum peat: 30 bark : 10 perlite (by vol.) amended with 5.5 g·L−1 dolomitic limestone and 0.5 g·L−1 granular wetting agent. This base substrate was either not amended with additional fertilizer (control) or amended with 0.59 kg·m−3 N of a CRF (Osmocote 18N–1.3P–5K) that was either ground (CRF-G) or whole prills (CRF-P). Substrates had initial moisture contents (IMCs) of 25%, 45%, or 65% and were stored at temperatures of either 20 or 40 °C. IMC and fertilizer type affected pH, electrical conductivity (EC), and nutrient release. Substrate pH increased with increasing IMC due to greater lime reactivity. About 25% of N from CRF-G treatments was immobilized between 2 and 14 days of storage. Low moisture content of bags, due to low IMC or storage at 40 °C, reduced the rate of N release from CRF-P treatments. Substrate P was rapidly immobilized by microbial communities.

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Ka Yeon Jeong, Claudio Pasian and David Tay

Substrate pH of soilless media directly affects nutrient availability. Limited information about the effect of substrate pH on growth of begonia species (not cultivated hybrids) was found in the literature. The objective of this study was to evaluate the effect of substrate pH on the growth and quality of six begonia species grown from June to Aug. 2004. The targeted pH ranges (<4.5, 4.5∼5.0, 5.0∼5.5, 5.5∼6.0, 6.0∼6.5, 6.5∼7.0, and over 7.0) of the peat-based substrates were obtained by adding seven different amounts of dolomitic hydrated lime: 0, 1.0, 1.3, 1.6, 2.0, 2.4, and 2.6 kg·m3. Begonia albopicta, B. cucullata var. cucullata, B. echinosepala var. elongatifolia, B. holtonis, B. fuchsioides (red), and B. fuchsioides (pink), were propagated by stem cuttings, and then transplanted into plastic containers. This experiment was a factorial experiment arranged in a randomized complete-block design. The pH was monitored weekly using the pour-through method and adjusted accordingly by adding flowable lime or a mild sulfuric acid solution. The pH values were averaged for each treatment of each species. There were significant differences between species in the inflorescence number and SPAD readings, but no interaction between species and substrate pH was found. Stem length, leaf area, and dry weight of each plant were significantly affected by species and substrate pH. B. albopicta performed best at substrate pH of 5.6 and 6.0, showing no symptoms of phytotoxicity. B. cucullata, above substrate pH 6.0, and B. holtonis at pH 5.0 and 5.6 had the highest vegetative growth and plant quality. Plant mortality was observed for B. cucullata and B. fuchsioides (red) at pH below 4.4 and 5.3, respectively.

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James E. Altland and Ka Yeon Jeong

Bagged potting mixes can be stored for weeks or months before being used by consumers. Some bagged potting mixes are amended with organic fertilizers such as poultry litter (PL), although there is little knowledge about how these and other organic fertilizers release in the substrate while in storage. The objective of this research was to determine nutrient availability from an organic PL fertilizer in a bagged potting substrate stored at different temperatures and with varying initial moisture content (IMC). The base substrate composed of 60 sphagnum peat : 30 bark : 10 perlite (by vol.) amended with 5.5 g·L−1 dolomitic limestone and 0.5 g·L−1 granular wetting agent. This base substrate was either not amended with additional fertilizer [nonfertilized control (NFC)] or amended with a PL fertilizer (microSTART60, 3N–0.9P–2.5K) in its original pelletized form (PL-P) or ground (PL-G), or an uncoated prill fertilizer (UPF, 15N–6.5P–12.5K). Substrates had IMCs of 25%, 45%, or 65% (by weight) and were stored at either 20 or 40 °C. The UPF treatment resulted in lower pH, higher electrical conductivity (EC), and higher percent recovered nitrogen (N) compared with other treatments, as was expected with a readily soluble fertilizer. Poultry litter particle size had no effect on any of the measured chemical properties of the stored substrates. Both PL fertilizer treatments resulted in pH similar to or lower than the NFC. The two PL fertilizers had higher EC throughout the experiment (1.59–2.76 mS·cm−1) than NFC (0.13–0.35 mS·cm−1). Poultry litter fertilizer provided a stable source of N in bagged potting mix over a range of IMC and storage temperatures, with little change in total N released over time.

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Ka Yeon Jeong, Claudio Pasian and David Tay

There is limited information on optimal substrate EC level for begonia species (noncultivated hybrids). The objective of this study was to evaluate the response of six species to different substrate EC in a greenhouse. Begonia albopicta, B. cucullata var. cucullata, B. echinosepala var. elongatifolia, B. holtonis, B. fuchsioides (red) and B. fuchsioides (pink) plants were propagated by stem cuttings, and transplanted into plastic pots using a soilless mix. Five concentrations (20, 80, 200, 400, and 600 mg·L-1 N) of 17–5–17 fertilizer were applied as irrigation water to derive the five substrate EC levels. This experiment was a factorial randomized complete-block design. Substrate EC was measured weekly using the PourThru method and averaged for each treatment of each species. Inflorescence number, the longest stem length, SPAD readings, leaf area, and dry weight of each plant were measured as growth parameters. There were significant responses to substrate EC level and species on begonia growth parameters. The highest growth parameters of B. albopicta and B. cucullata were obtained at EC 5.7 and 6.6 mS·cm-1, respectively. The maximum growth of B. echinosepala and B. holtonis was observed at 2.6 and 3.0 mS·cm-1, respectively. B. fuchsioides, grown at 1.2 mS·cm-1, had the best growth parameter values. As EC level increased, SPAD value for B. fuchsioides (pink) and B. holtonis also increased. The highest SPAD reading was observed at EC 3.7 mS·cm-1 for B. albopicta, EC 6.6 mS·cm-1 for B. cucullata, EC 2.6 mS·cm-1 for B. echinosepala, and EC 4.1 mS·cm-1 for B. fuchsioides (red). Plant mortality of several begonia species was observed when grown at EC value above 6.4 or below 4.4 mS·cm-1.

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Ka Yeon Jeong, Paul V. Nelson, Carl E. Niedziela Jr. and David A. Dickey

The objective of this study was to determine how plant species, fertilizer potential acidity/basicity rating (PABR), and fertilizer concentration affect root substrate pH. Three experiments were conducted. In the first experiment, 13 herbaceous species were grown in a root substrate of three sphagnum peatmoss: one perlite (v/v) with deionized water and a neutral fertilizer (NF) with a PABR of 0 for 78 days to determine species relationships to substrate pH. The decrease in substrate pH ranged from 0.14 to 2.45 units, depending on species. In the second experiment, four of the 13 species from the previous trial representing the range of pH suppression were grown under similar growth conditions as the first experiment for 70 days. Substrate pH was lowered in the range of 0.47 to 2.72 units. In the third experiment, three fertilizers with PABRs of 150 kg·t−1 CaCO3 equivalent alkalinity, 0 neutral, and 193 kg·t−1 CaCO3 equivalent acidity were applied in a factorial design at 100 and 200 mg·L−1 N at each irrigation to kalanchoe (the species with the greatest pH suppression from the previous experiments) for 56 days. When applied at the lower fertilizer rate (100 mg·L−1 N), the PABRs resulted in the final substrate pH levels of 4.68, 5.60, and 6.11 for the acidic fertilizer (AF), NF, and basic fertilizer (BF), respectively. At the high fertilizer rate (200 mg·L−1 N), substrate pH declined continuously to 3.97, 4.03, and 4.92 for the AF, NF, and BF, respectively. Expression of PABR depended on the balance between the abiotic (chemical) effect of the fertilizers vs. the biotic (physiological) effects of the fertilizers on microbes and plants. The PABR was best expressed when the fertilizer supply was just adequate or lower indicating a closer connection to the biotic effect.