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  • Author or Editor: Thomas Yeager x
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Cycas revoluta, an important ornamental palm-like plant of warmer regions of the world, often exhibits a foliar chlorotic/necrotic dieback in landscapes. Despite a weak correlation (r2 ≤ 0.28) of percent symptoms with soil nutrient levels or pH, symptom severity was correlated more notably (r2 =0.49) with Mn and had even a higher correlation (r2 = 0.61) with the Fe : Mn ratio. Anatomical examination of chlorotic leaflets indicated an accumulation of tanniniferous cells but did not provide direct evidence of Mn deficiency. Although field surveys indicated a link between low Mn levels and Fe : Mn ratio in the plant and appearance of the disorder, the manifestation of symptoms could not be directly correlated with any edaphic factors. However, identical symptoms were induced in young plants by withholding Mn in a solution culture experiment. Application of chelated Mn on expanding leaves alleviated the disorder, but only for the current growth flush. Irrigation frequency in concert with other cultural practices probably are more responsible for development of symptoms than actual soil Mn inadequacy. In consideration of acute susceptibility of cycads to micronutrient deficiencies, plants should be supplied with a complete micronutrient fertilizer during growth in containers and before field planting.

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Dwarf burford holly (Ilex cornuta `Burfordii Nana') fertilized with N at 22.1 g per container yearly during production in the nursery generated more new shoot weight but less root weight after transplanting to a landscape than those receiving N at 14.8 g per container yearly. Slicing the root ball at planting, compared to not slicing, resulted in comparable regenerated root weight but reduced new shoot number, new shoot dry weight, and new shoot:regenerated root dry-weight ratio when irrigation was not applied daily after transplanting. Although irrigation frequency did not impact total weight of regenerated roots into landscape soil, more roots grew from the bottom half of the root ball when plants were irrigated periodically after planting than when plants received daily irrigation. Plants irrigated other than daily produced fewer shoots and less shoot weight than those receiving irrigation daily after transplanting. When plants were without irrigation for 4 or 6 days in the first week after transplanting, those planted without the nursery container on the root ball were more stressed (more negative xylem potential) than those planted with the container still on the root ball. However, 2 weeks later, plants without the nursery container were less stressed due to root growth into landscape soil.

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Vinca [Catharanthus roseus (L.) G. Don], salvia (Salvia splendens F. Sellow ex Roem. and Schult.), Dwarf Yaupon holly (Ilex vomitoria Ait. ‘Nana’), and ‘Helleri’ holly (Ilex crenata Thunb. ‘Helleri’) were grown in 2.3-L containers with soilless substrates in a greenhouse. Irrigation was applied as needed to the substrate surface or applied to the substrate surface and applied over plant foliage. Irrigation for both application methods was composed of 0%, 25%, 50%, 75%, or 100% reclaimed water (processed sewage) with deionized water composing the remainder. Shoot dry weights of marketable-sized plants were either larger or similar when 100% reclaimed water was used compared with 0% reclaimed water (deionized). Root dry weights exhibited a similar response except for salvia roots that were smaller with 100% reclaimed water irrigation regardless of application method. Leachate NO3-N, phosphorus (P), and potassium (K) generally decreased throughout the experiments for vinca and Dwarf Yaupon holly and were highest at experiment midpoint for ‘Helleri’ holly and lowest for salvia. Leachate electrical conductivities (ECs) were generally highest at experiment termination for vinca and salvia, whereas ECs of Dwarf Yaupon and ‘Helleri’ holly tended to peak at experimental midpoint and then decrease slightly at termination. ECs were usually less than 2 dS·m−1 except at experimental midpoint (4.5 months) for ‘Helleri’ holly. Based on the response of plants in this research, high-quality reclaimed water is a viable water source for annual and woody container-grown nursery crops.

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The capacity for evapotranspiration (ET)-based irrigation scheduling to reduce runoff volume and nutrient leaching was tested in Fall 2004 and Spring 2005. Runoff (container leachate plus unintercepted irrigation and precipitation) was collected continuously for 17 weeks during production of sweet viburnum [Viburnum odoratissimum (L.) Ker Gawl.] in 2.4-L (16-cm top diameter) containers fertilized with an 18N–2.6P–10K polymer-coated, controlled-release fertilizer. Treatments were a factorial arrangement of two irrigation rates (fixed rate of 1 cm·d−1 or a variable, ET-based rate) and two fertilizer rates (15 or 30 g/container in 2004 and 10 or 15 g/container in 2005). Averaged over the two experiments and compared with the 1-cm·d−1 rate, ET-based irrigation reduced the amount of irrigation water applied (L/container) by 39% and runoff volume (L/container) by 42% with greatest reductions observed during the second half of the 2004 experiment and the first half of the 2005 experiment. Compared with 1-cm·d−1 rate, ET-based irrigation reduced runoff nitrogen (N), phosphorus (P), and potassium (K) (mg/container) by 16%, 25%, and 22%, respectively, in 2004 and runoff K 15% in 2005 with irrigation effects varying on a weekly basis. Irrigation treatments did not affect the response of plants to fertilizer rate. Because shoot dry weight was unaffected by irrigation treatments, results indicate that compared with a fixed irrigation rate, ET-based irrigation can reduce irrigation and runoff volumes and to a lesser extent nutrient loss while providing adequate water for plant growth.

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As limitations on water used by container nurseries become commonplace, nurseries will have to improve irrigation management. Several ways to conserve water and improve on the management of irrigation water applied to container plants are discussed in this review. They include 1) uniform application, 2) proper scheduling of irrigation water, 3) substrate amendments that retain water, 4) reducing heat load or evaporative loss from containers, and 5) recycling runoff water.

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Irrigation runoff water from a containerized landscape plant production bed was blended with rainwater from green house roofs in a constructed collection basin. Water from both the collection basin and an on-site potable well were characterized and used to grow foliage and bedding plants with overhead and ebb-and-flow irrigation systems. Over a 2-year period, a total of 18 foliage and 8 bedding plant cultivars were produced with plant growth and quality quantified. Alkalinity, electrical conductivity, hardness, and concentrations of nutrients of water from both sources were well within desired levels for greenhouse crop production. Turbidity and pH were relatively high from algal growth in the collection basin. However, substrate pH, irrigated by either water source, remained between 6 and 7 throughout the production periods. All plants at the time of finishing were of marketable sizes and salable quality independent of water source. No disease incidences or growth disorders related to water sources were observed. Results suggest that captured irrigation runoff blended with rainwater can be an alternative water source for green house crop production.

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The objective of these experiments was to evaluate the use of tensiometers to monitor substrate moisture tensions for Metro-Mix 500 and 2 pine bark: 1 Canadian peat: 1 sand (PBPS, by volume) used for container-grown azalea Rhododendron indicum L. `Mrs. G.G. Gerbing' and chrysanthemum (Dendranthema grandiflora Tzvelez.) `Coral Charm.' Commercially available ceramic cups of two sizes, small [0.374 inch (0.95 cm) diameter and 1.125 inches (2.86 cm) long] and large [0.874 inch (2.22 cm) diameter and 3.0 inches (7.62 cm) long] were used to construct pressure transducer-equipped tensiometers. Data from these greenhouse experiments, indicate that either the small or large ceramic cup could be used to monitor substrate tensions at which water would be available to container-grown plants.

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The objective was to quantify the effect of the timing of macronutrient applications on nutrient uptake, growth, and development of Petunia ×hybrida Hort. Vilm.-Andr. ‘Supertunia Royal Velvet’ during vegetative propagation. Starting with unrooted cuttings (Day 0), fertigation was applied continuously at three time intervals (Day 0 to 7, Day 8 to 14, or Day 15 to 21) using either a “complete” (C) water-soluble fertilizer containing (in mg·L−1) 75 NO3-N, 25 NH4-N, 12 phosphorus (P), 83 potassium (K), 20 calcium (Ca), 10 magnesium (Mg), 1.4 sulfur (S), 2 iron (Fe), 1 manganese (Mn), 1 zinc (Zn), 0.5 copper (Cu), 0.5 boron (B), and 0.2 molybdenum (Mo) or a micronutrient fertilizer (M) containing (in mg·L−1) 1.4 S, 2 Fe, 1 Mn, 1 Zn, 0.5 Cu, 0.5 B, and 0.2 Mo in a complete factorial arrangement. With constant fertigation using the C fertilizer, plant dry weight (DW) doubled from Day 0 (sticking of unrooted cuttings) to Day 7 (0.020 g to 0.047 g), root emergence was observed by Day 4, and by Day 7, the average length of primary roots was 2.6 cm. During any week that the M fertilizer was substituted for the C fertilizer, tissue N–P–K concentrations decreased compared with plants receiving the C fertilizer. For example, plants receiving the M fertilizer between Day 0 and 7 had 20% lower tissue-N concentration at Day 7 compared with those receiving the C fertilizer. Although both shoot DW and leaf count increased once macronutrient fertilization was resumed after Day 7, final shoot DW and leaf count were lower than plants receiving C fertilizer from Day 0 to 21. Time to first root emergence was unaffected by fertigation. Constant application of C resulted in a higher shoot-to-root ratio at Day 21 than all other treatments. Results emphasize the importance of early fertigation on petunia, a fast-rooting species, to maintain tissue nutrient levels within recommended ranges.

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Increasing environmental concerns and legislation in many states and in other countries require that we take a more comprehensive sustainable “best management” approach to production techniques in nursery and greenhouse operations. This is particularly important because these production facilities are typically intense users of resources that are applied to relatively small land areas. We have developed an online knowledge center to facilitate the implementation of more sustainable practices within the nursery and greenhouse industry. A web-based knowledge center provides the most cost-effective mechanism for information delivery, as our potential audiences are extremely diverse and widespread. We currently have a registered user database of over 450 educators, growers, and industry professionals, and undergraduate and graduate students. A gateway website provides an overview of the issues and the goals of the project. The associated knowledge center currently has 25 in-depth learning modules, designed in a Moodle learning management framework. These learning modules are designed to actively engage learners in topics on substrate, irrigation, surface water, and nutrient and crop health management, which are integral to formulating farm-specific strategies for more sustainable water and nutrient management practices. Additional modules provide assessment and implementation tools for irrigation audits, irrigation methods and technologies, and water and nutrient management planning. The instructional design of the learning modules was paramount because there can be multiple strategies to improve site-specific production practices, which often require an integration of knowledge from engineering, plant science, and plant pathology disciplines. The assessment and review of current practices, and the decision to change a practice, are often not linear, nor simple. All modules were designed with this process in mind, and include numerous resources [pictures, diagrams, case studies, and assessment tools (e.g., spreadsheets and example calculations)] to enable the learner to fully understand all of the options available and to think critically about his/her decisions. Sixteen of the modules were used to teach an intensive 400-level “Principles of Water and Nutrient Management” course at the University of Maryland during Spring 2008 and 2009. The water and nutrient management planning module also supports the nursery and greenhouse Farmer Training Certification program in Maryland. The Maryland Department of Agriculture provides continuing education credits for all consultants and growers who register and complete any module in the knowledge center. Although these learning resources were developed by faculty in the eastern region of the United States, much of the information is applicable to more widespread audiences.

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