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Environmental concerns with nitrogen and phosphorus use at container nurseries and the subsequent effects of nutrient-laden irrigation effluent prompted this study. Bare root liners of willow oak (Quercus phellos L.) and sweetbay magnolia (Magnolia virginiana L.) were grown in #5 containers during year one and repotted into #15 containers during year two using 100% pine bark or pine bark: peat substrate (4:1 by volume). Two fertilizer sources, Osmocote 19N–2.2P–7.5K (19–5–9) or Harrell's 17N–2.2P–10.0K (17-5-12), were included in the container substrate in a fluoropolymer bag with 17 g N in each #5 container and 63 g N in each #15 container. Using a split plot design with fertilizer and media as subplots, a cyclic irrigation regime consisting of three irrigation applications spaced one hour apart was compared to a traditional irrigation regime with one irrigation application that equaled the total volume applied in the cyclic regime. Fertilizer source influenced cumulative amounts (mg/year) of ammonium-N, nitrate-N and orthophosphate in the container leachate. Nitrate-N and ammonium-N from Harrell's 17N–2.2P–10.0K fertilizer were each ≈20% higher in the container leachate from sweetbay magnolia than Osmocote 19N-2.2P-7.5K fertilizer. In the case of the willow oak, the differences were 32% and 19%, respectively. Orthophosphate averaged about 65% greater in leachate from both sweetbay magnolia and willow oak containers when grown with Osmocote compared to Harrell's fertilizer. At the end of year two, height and caliper growth were similar among treatments with both species.

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Chrysanthemums, cultivars Red Grenadine and Buckaroo, were produced in 15 cm pots in the greenhouse and fertilized with a 210 mg/l N solution at a volume of either 550 ml or 1000 ml. The nutrient solution applied to half the pots contained a wetting agent (AquaGro L), the remaining pots received no wetting agent. Soil core samples were removed, at 15 cm increments to a depth of 90 cm, from the soil profile underlying each treatment group. Leachate samples were collected and the volume and NO3-N content determined. Final and mid-term plant dry weight were determined, and the tissues (leaves and flowers) were analyzed for NO3-N and total nitrogen content. The leachate fraction (LF) from pots receiving a wetting agent (WA) was greater (p<0.05) than from pots receiving no WA (29.1% vs 26.4% respectively). However, WA did not greatly affect the amount of NO3-N in container effluent or the total NO3-N deposited on the soil underlying the crop; these were most influenced by LF. NO3-N content in the upper 15cm soil zone under pots irrigated to a high LF was higher than under the low LF pots after two weeks and by week 10 (end of the study) significant differences were measured in the 30-45 cm soil zone. At final harvest, significant differences in plant dry weight, potting medium NO3-N, and plant total N content were observed in response to both LF and WA treatments.

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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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Ground water contamination resulting from continuous liquid fertilization technologies is a serious problem facing greenhouse growers in the United States. Rooted Dendranthema grandiflora Tzvelev. cultivar 'Iridon' cuttings were transplanted into 11 cm pots filled with a 50% peatmoss and 50% perlite (v/v) media containing 0.10, 0.21, 0.42, or 0.84 g N from a controlled release 12-10-17 plus minors fertilizer deposited directly below the transplanted cutting. Pots were assigned to a top-water or subirrigation treatment.

Subirrigation reduced the nitrate leachate concentration by as much as 250 ppm as compared with top-watering. Fertilizer N rate linearly decreased plant height in both of the irrigation treatments. Final dry weight of the shoot peaked at the 0.21 g N rate in both the irrigation treatments.

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Abstract

Fertilizer levels of 500-220-400 and 750-330-600 mg/liter N-P-K reduced growth of Brassaia, Chamaedorea and Peperomia when compared to 250-110-200 mg/liter but had no effect on Philodendron and Maranta. As fertilization level increased, pH of the leachate decreased and soluble salts increased. As fertilizer level increased, leachate increased from pots with Brassaia and Peperomia and to a lesser extent from Maranta and leachate from Philodendron and Chamaedorea were similar. Fertilizer of 800-360-680 mg/liter N-P-K reduced fresh weight and root grade of Peperomia and Brassaia. Amount of leachate doubled as fertilizer and volume of water applied increased.

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Abstract

Extensive losses in N applied to container-grown woody ornamental plants prompted this investigation to determine a) leaching of N from urea (U) and isobutylidene diurea (IBDU); b) influence of nitrapyrin (NI), a nitrification inhibitor, on N leaching losses from U; and c) to evaluate influences of these materials on growth, quality, and N uptake by Rhododendron obtusum Lindl. cv. Hinodegiri. In root medium composed of 60 pine bark : 30 sand : 10 soil (by volume), 48.8% of applied N from U was leached after 87 days, whereas leachate losses of N from IBDU and U + NI were 42.3% and 37.2%, respectively. All plants attained marketable quality by the end of the study. Azaleas fertilized with IBDU were of significantly higher quality on days 70 and 77 than those treated with U + NI and higher quality on days 77, 84, and 87 than those treated with U. No differences were found in shoot dry weight or N content in shoot tissues.

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Commercial apple (Malus domestica Borkh.) orchards in the northeastern United States receive heavy pesticide inputs and are often located on well-drained soils near surface and groundwater resources. Nonpoint-source water pollution by agrichemicals has been monitored in agronomic crop systems and simulated using computer models and laboratory soil columns, but inadequately studied at field scale in orchards. We monitored the concentrations of agrichemical tracers, nitrate-N, and benomyl fungicide in water samples from two apple orchards under mowed sodgrass (Mowed-Sod), shredded bark mulch (Bark-Mulch), preemergence residual herbicides (Resid-Herb), and postemergence herbicide (Post-Herb) groundcover management systems (GMSs). In one orchard, we evaluated subsurface spatial patterns and flow rates of a weakly adsorbed blue dye (pesticide analog) and potassium bromide (nitrate analog) under trees after six years of Post-Herb and Mowed-Sod treatments. Nitrate and pesticide tracers leached more rapidly and in higher concentrations under Post-Herb treatments, apparently via preferential macropore flowpaths such as root channels, soil cracks, and macrofauna burrows. At another orchard, we monitored subsurface leaching and surface runoff of benomyl and nitrate-N on a whole-field scale. Peak concentrations of benomyl (up to 29 mg·liter-1) and nitrates (up to 20 mg·liter-1) were observed in subsoil leachate under Resid-Herb plots during 1993. In 1994, nitrate concentrations were greater in leachate from all GMSs, with upper ranges from 48 to 66 mg·liter-1, while benomyl concentrations were lower in all GMSs compared with the previous summer. In surface water runoff during 1993, the highest benomyl concentrations (387 mg·liter-1) and most frequent outflows occurred in Resid-Herb plots. During 1994, benomyl runoff was more frequent in both herbicide GMSs, with concentrations up to 61 mg·liter-1 observed in the Post-Herb plots. Weather patterns, irrigation intensity, differing soil conditions under each GMS, and the turfgrass/clover drive lanes affected the relative frequency and concentrations of benomyl and nitrate leaching and runoff. Preferential bypass flow appeared to be a major subsurface leaching pathway, and erosion sediment an important factor in surface movement of these agrichemicals. Our studies suggest that nitrate-N and benomyl fungicide may be more prone to leaching or runoff from orchard soils under some herbicide GMSs in comparison with mowed sodgrass or biomass mulch systems.

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Five container substrates—3 pine bark (PB) : 1 peat (PT) : 1 sand (SD), 3 PB : 1 recycled paper (RP) : 1 SD, 2 PB : 2 RP : 1 SD, 3 vermiculite (VM) : 1 RP : 1 SD, and 2VM : 2 RP : 1 SD—were used to grow rose-of-sharon (Hibiscus syracus L. `Double Purple') and forsythia (Forsythia ×intermedia Zab. `Lynwood Gold') for 4.5 months. The control substrate (3 PB:1 PT:1 SD) had higher concentrations of NH4 * in leachate than other substrates at each of four sample times during the growing season except 4 Aug. Leaf number and leaf area per plant and height of rose-of-sharon were greater and the leaf area per leaf was smaller in all substrates containing recycled paper than in substrates without recycled paper. Forsythia plants had greater stem and root dry weights and were taller in substrata without recycled paper than plants in substrates with recycled paper. Processed recycled paper is a possible component for container nursery plant production, but further testing on a large number of species is needed before widespread implementation.

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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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Leaching of N into ground water has become a major pollutant in several areas of the U.S. The potential for regulation of environmental plant producers is increasing, but limited information is available on cultural management. This factorial experiment tested a liquid and a slow release fertilizer source at 3 irrigation levels (100, 200 or 300 ml/20 cm pot/2 times/wk) for NH4 +, NO3 - and P found in leachate collected weekly for 12 weeks. Plant quality and fresh weight for all treatments was similar, but large variations occurred in NH4 +, NO3 - and P levels in leachate due to irrigation level. Increasing irrigation level from 100 to 300 ml twice weekly resulted mainly in linear increases of NO3 - present in leachate, with levels as high as 159 mg/l observed near the end of the production cycle. NH4 + levels were most affected by irrigation and highest early in the experiment, but were generally lower than 1 mg/l. P levels ranged from 1.4 to 16.0 mg/l in leachate with responses to fertilizer source and irrigation mainly during the first 6 weeks.

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