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Donald J. Merhaut and Julie P. Newman

Lilies are produced throughout the year in coastal areas of California.

Cultural practices involve daily applications of water and fertilizer, using both controlled release fertilizers (CRF) and liquid fertilizers (LF). However, many production facilities are in proximity to coastal wetlands and are therefore at greater risk of causing nitrogen pollution via runoff and leaching. Due to federal and state regulations, nurseries must present a plan of best management practices (BMPs) to mitigate nutrient runoff and leaching and begin implementing these practices in the next 2 years. In the following studies, we determined the potential for nitrate leaching from four different types of substrates (coir, coir: peat, peat, and native soil). There were four replications of each treatment, with a replication consisting of one crate planted with 25 bulbs. Two cultivars were used in two separate experiments, `Star Fighter' and `Casa Blanca'. Nitrate leaching was determined by placing an ion-exchange resin bag under each crate at the beginning of the study. After plant harvest (14–16 weeks), resin bags were collected and analyzed for nitrate content. Plant tissues were dried and ground and analyzed for nitrogen content. Based on the results of these studies, it appears that the use of coir, peat, and soil may not influence plant growth significantly. Substrate type may mitigate the amount of nitrate leaching through the media. However, the cultivar type may also influence the degree of nitrate mitigation, since leaching results varied between the two cultivars.

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Julie P. Newman, J. Heinrich Lieth and Ben Faher

An irrigation system for monitoring and controlling soil moisture tension in the root zones of potted plants using computer and solid-state tensiometer technologies was evaluated in a commercial greenhouse on 'V-14 Glory' poinsettias over a 10 week period. Replicated benches with separate drip circuits controlled by the computer maintained the soil moisture tension of the potted poinsettia plants between 1 kPa and 5 kPa. The amount of water used by each bench and the amount leached was compared to benches with separate drip circuits that were manually operated by the grower according to standard commercial practice. There was a 65% savings in the total amount of water used for the computer-controlled system and an average weekly reduction of 98.6% in leachate. The differences were significant and there was no measurable reduction in plant quality, even though soil analyses showed slightly elevated EC levels.

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Julie P. Newman, Michael S. Reid and Linda Dodge

Commercial formulations of silver thiosulfate (STS) were evaluated for their efficacy in promoting postharvest longevity of gypsophila. Argylene, Chrysal AVB, Chrysal OVB, Oasis Dry Flower Conditioner, Rogard RS, and Silflor were compared to the anionic STS complex and to Physan plus sucrose. Flowers were pulse treated, then placed overnight at 2° C in Physan plus sucrose. Flowers treated with Rogard RS, Chrysal OVB, and Physan were held continuously in the solution. Overnight treatments of STS were compared to short pulses at higher concentrations. To simulate the effect of shipment, treated flowers were packed in boxes, then held either for 48 hours at room temperature (12-18° C) or for 60 hours in a range of ethylene concentrations. Individual stems were then placed in Physan plus sucrose. The number of open flowers, buds, and dead flowers was determined on each stem at various intervals. All products effectively extended the display life of gypsophila except Rogard RS and Chrysal OVB. Although overnight treatments with STS formulations were not as effective as pulse treatments, their convenience could warrant commercial use.

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Julie P. Newman, Linda L. Dodge and Michael S. Reid

Commercial floral products with claimed anti-ethylene effects were evaluated for their efficacy in promoting postharvest longevity of gypsophila (`Perfecta', `Gilboa', and `Golan' baby's breath, Gypsophila paniculata L.). These products were applied according to label directions and compared to a laboratory preparation of silver thiosulfate (STS) prepared as a short pulse treatment and as an overnight treatment; they were also compared to the new anti-ethylene gas, 1-methylcyclopropene (1-MCP). After these pretreatments, the flowers were exposed to ambient air or to 0.7 ppm ethylene gas for 36 hours; other flowers received a simulated shipping treatment. Products containing adequate concentrations of silver consistently extended the display life of gypsophila. Products with low concentrations of silver (<10 ppm) or containing aminoethoxyvinylglycine (AVG) offered no more protection than treatments without anti-ethylene compounds. Overnight treatments with STS were as effective as short pulse treatments. Although 1-MCP pretreatment helped prevent the effects of ethylene on flowers that were open at the time of pretreatment, it provided no protection for buds that opened subsequently. There were no marked differences in ethylene sensitivity among three gypsophila cultivars.

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Julie P. Newman, Joseph P. Albano, Donald J. Merhaut and Eugene K. Blythe

Release characteristics of four different polymer-coated fertilizers (Multicote, Nutricote, Osmocote, and Polyon) were studied over a 47-week period in a simulated outdoor, containerized plant production system. The 2.4-L containers, filled with high-fertility, neutral-pH substrate, were placed on benches outdoors to simulate the environmental conditions often used for sun-tolerant, woody perennials grown in the southwestern United States. Container leachates were collected weekly and monitored for electrical conductivity, pH, and concentrations of NH4 +N, NO3 N, total P, and total K. Concentrations of most nutrients in leachates were relatively high, but fluctuated frequently during the first third of the study period, and then gradually decreased and stabilized during the last 27 weeks. Osmocote often resulted in greater NH4 + and total inorganic N concentrations in leachates than other fertilizers during weeks 1 through 5, whereas Multicote produced higher NH4 + in leachates than most of the other fertilizer types during weeks 9 through 12. Overall, total P concentrations were greater with Multicote during a third of the experimental period, especially when compared with Osmocote and Polyon. Differences were also observed among treatments for leachate concentrations of K, with Polyon and Multicote fertilizers producing greater K concentrations in leachates compared with Osmocote during several weeks throughout the experimental period. Leachate concentrations of NO3 N and P from all fertilizer types were usually high, especially from week 5 through week 30.

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Joseph P. Albano, Donald J. Merhaut, Eugene K. Blythe and Julie P. Newman

Nutrient release characteristics of four different controlled-release fertilizers (Osmocote, Nutricote, Polyon, and Multicote) were monitored during an 11-month period in a simulated outdoor nursery production facility. Although no plants were used in the experiment, fertilization rates, irrigation regimes, and cultural practices simulated those typically used to produce fast-growing, high-nutrient-requiring containerized woody ornamentals. Fertilizer prill release characteristics were monitored through analyses of leachates, which were collected weekly. Concentrations of Mg, Mn, Zn, Cu, and Mo were relatively high during the first 5 to 10 weeks of the experiment, then declined and usually stabilized during the remainder of the study. However, Mn and Zn displayed erratic increases in concentrations several times throughout the study. Calcium concentrations did not increase until the fifth week, rapidly peaked to about 300 mg·L–1, and then decreased and leveled off to ≈80 to 100 mg·L–1 during the remainder of the study. Several significant differences were observed between treatments. The Osmocote treatment had significantly greater Ca and Mg concentrations in the leachate than the other fertilizer types during the last 6 weeks of the study, whereas the Nutricote treatment often had significantly greater Fe concentrations than leachates from other treatments, especially during the last 26 to 35 weeks of the study, and significantly greater Zn concentrations than the other CRFs during the last 21 weeks of the study. Based upon U.S. Environmental Protection Agency guidelines, concentrations of Fe were often more than the allowable limit of 0.3 mg·L–1 with all fertilizer types, but especially with Nutricote. Concentrations of Mn and Cu also exceeded federal guidelines, particularly during the first several weeks of the study.

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Donald J. Merhaut, Eugene K. Blythe, Julie P. Newman and Joseph P. Albano

Release characteristics of four types of controlled-release fertilizers (Osmocote, Nutricote, Polyon, and Multicote) were studied during a 47-week simulated plant production cycle. The 2.4-L containers containing a low-fertility, acid-based substrate were placed in an unheated greenhouse and subjected to environmental conditions often used for production of azaleas and camellias. Leachate from containers was collected weekly and monitored for pH, electrical conductivity, and concentrations of NH4 + N, NO3 N, total P and total K. Leachate concentrations of all nutrients were relatively high during the first 10 to 20 weeks of the study, and then gradually decreased during the remaining portion of the experiment. Differences were observed among fertilizer types, with Multicote often resulting in higher concentrations of N, P, and K in leachates compared to the leachates from the other fertilizer types during the first half of the study. Concentrations of NO3 and P from all fertilizer types were often above permissible levels as cited in the federal Clean Water Act.

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Eugene K. Blythe, Donald J. Merhaut, Julie P. Newman and Joseph P. Albano

Leachate from containerized substrate containing one of four different controlled-release fertilizers (Osmocote, Nutricote, Polyon, or Multicote) were monitored for concentrations of Ca, Mg, Fe, Mn, Zn, Cu, and Mo during a 47-week period. Environmental and cultural practices simulated an unheated greenhouse production program typically used for low-nutrient-requiring crops such as azalea and camellia. Leachate concentrations of all nutrients were relatively high during the first 10 to 20 weeks of the study, and then gradually decreased during the remaining portion of the experiment. Few differences were observed among fertilizer types. Of the elements monitored, only Fe and Mn leachate concentrations were above critical levels specified in the Clean Water Act by the U.S. EPA.

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Salvatore S. Mangiafico, Jay Gan, Laosheng Wu, Jianhang Lu, Julie P. Newman, Ben Faber, Donald J. Merhaut and Richard Evans

Production nurseries may be significant sources of nutrients and pesticides in runoff as a result of the intensity at which fertilizers, pesticides, and irrigation water are applied. Concentrations of nutrients and pesticides in runoff from production nurseries are not extensively documented. Runoff from 11 production nurseries in southern California using either recycling or detention basins was monitored for nutrients and pesticides. For six sites, runoff volume was determined and nutrient loads in runoff were calculated. Water use data, percentage of water recycled, and construction costs were determined for sites with recycling systems. Nutrient concentrations, mass loads, and pesticide detections in runoff from some sites would have been of concern without the implementation of detention or recycle basins. There were few differences in nutrient concentrations or pesticide detections between runoff from irrigation and that from precipitation events. This suggests the need for management practices and technologies that address runoff from both irrigation and precipitation events. Water use and cost data suggested that the implementation of recycling systems may be more beneficial and cost-efficient for larger facilities.