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Darren L. Haver and Ursula K. Schuch

Salt-sensitive (`Illusion') and salt-tolerant (`Blazon') New Guinea impatiens cultivars were grown for 70 days with a controlled-release fertilizer at 3.3, 6.6, or 9.9 g/pot under constant media moisture of 1–3 kPa or 4–6 kPa. Optimum growth for both cultivars occurred using 6.6 g/pot and a media moisture level of 1–3 kPa. The leaf area (LA), leaf number (LN), leaf dry weight (LDW), stem dry weight (SDW), and root dry weight (RDW) were significantly reduced at 9.9 g/pot in `Illusion', with values similar to those at 3.3 g/pot. LDW, SDW, RDW, LA, and LN were similar for 6.6 g/pot and 9.9 g/pot in `Blazon'. At 4–6 kPa LDW, SDW, RDW, LA, and LN decreased from low to high in `Illusion'. LA in `Blazon' also decreased from low to high, but LDW, SDW, RDW, and LN were unaffected. Media EC levels were greater in the upper half of the media regardless of moisture level. EC values as high as 7.3 dS·m–1 in the upper half of the media and as high as 5.2 dS·m–1 in the lower half of the media were measured without causing plant mortality.

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Darren L. Haver and Ursula K. Schuch

The objectives of this study were to determine 1) the minimum controlled-release fertilizer (CRF) rate and the lowest constant medium moisture required to produce the highest quality plants and 2) if this production system affected quality of these plants under two postproduction light levels. Two New Guinea impatiens (Impatiens sp. hybrids) `Illusion' and `Blazon' (Lasting Impressions Series) differing in salt tolerance were grown for 42 days with a CRF at three rates (3.3, 6.6, or 9.9 g/pot) and two medium moisture levels (low or high) without leaching. The high moisture level (tension setpoints of 1 to 3 kPa) and 6.6 g of CRF/pot produced optimum biomass. Low medium moisture (tension setpoints of 4 to 6 kPa) reduced leaf area, leaf number, leaf N content, root, stem, and leaf dry masses as CRF rate increased from low to high for `Illusion'. Similar results in `Blazon' were observed as CRF rates increased from 3.3 to 6.6 g. Biomass decreased no further at the high rate of 9.9 g/pot. Biomass increased in both cultivars under high medium moisture when CRF rates increased from 3.3 to 6.6 g. Biomass of `Illusion' decreased at 9.9 g/pot, although no symptoms of salt sensitivity were observed (i.e., leaf tip burn). `Blazon' maintained a similar biomass when amended with 9.9 or 6.6 g CRF/pot, although electrical conductivity (EC) in the medium was 5.9 dS·m-1 in the upper half and 4.1 dS·m-1 in the lower half of the medium at the end of production. Growth of `Illusion' responded more favorably to postproduction light levels that were similar to those of production regardless of treatment imposed during production. Similar biomass responses occurred for `Blazon' regardless of the postproduction light level.

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Janet S. Hartin, David W. Fujino, Lorence R. Oki, S. Karrie Reid, Charles A. Ingels, and Darren Haver

University of California (UC) researchers have been involved in research and extension pertaining to measuring evapotranspiration (ET) rates and determining the minimum irrigation requirements of landscape plants for more than 30 years. Early work included the design and implementation of the California Irrigation Management Information System (CIMIS) weather station network and determining crop coefficients for warm and cool season turfgrasses based on historical ET and CIMIS data. Other researchers determined the minimum irrigation requirements for several species of established landscape trees, shrubs, and groundcovers in diverse climate zones throughout the state. In addition, the Water Use Classification of Landscape Species (WUCOLS) system was developed by UC personnel in the early 1990s which, to date, has classified more than 3500 landscape species into very low, low, moderate, and high water-use categories based on observation and personal experience by industry experts and UC personnel. Future work in the area of landscape water use and conservation will include updating WUCOLS as more data from replicated trials become available. New research at UC Riverside aims to improve irrigation efficiency (IE) through precision irrigation using smart controllers, remote sensing, and geospatial analysis under controlled conditions. Irrigation training and certification for public and private landscape managers must remain a priority because, even with advanced smart controller technologies, water savings will not occur with poorly designed and functioning irrigation systems.