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- Author or Editor: Alex Niemiera x
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The pour-through (PT) nutrient extraction method involves collection of leachate at the container bottom that results from displacement of substrate solution by water applied to the substrate surface. The PT is a convenient and effective means of monitoring the nutritional status of the soilless container substrates used in the nursery industry, but is less convenient for large containers, particularly those used in the “pot-in-pot” system of growing trees in production containers within in-ground socket containers. We describe a simple vacuum method of extracting solution from pine bark in containers using ceramic cup samplers. When N was applied to a pine bark substrate at 56–280 mg/L, extractable N was slightly higher for the PT than for the ceramic cup method. The correlation between applied and extractable N was 0.99 for both methods. Further comparison of pine bark extract nutrient and pH levels for PT and ceramic cup methods will be presented.
Studies were conducted to evaluate the effect of water application medium moisture deficit, water application rate, and intermittent application on water application efficiency {[(amount applied - amount leached)/amount applied] x 100} of spray stake-irrigated, container-grown plants. Pine bark-filled containers were irrigated to replace moisture deficits of 600, 1200, or 1800 ml; deficits were returned in single, continuous applications of 148, 220, or 270 ml·min-l. Efficiency was unaffected by application rate but decreased with increased medium moisture deficit. In the second experiment, container medium at a 600-ml deficit was irrigated with 400 or 600 ml (6570 and 100% water replacement, respectively); deficits were returned in a single, continuous application or in intermittent 100-ml applications with 30-min intervals between irrigations. Application efficiency was greater with intermittent irrigation (95% and 84% for 400- and 600-ml replacement, respectively) than with continuous irrigation (84% and 67% for 400- and 600-ml replacement, respectively). In the third experiment, pine bark was irrigated with 600 ml water (100% replacement) in 50-, 100-, or 150-ml aliquots with 20, 40, or 60 min between applications in a factorial design. Efficiency increased with decreasing application volume and increasing time between applications. Highest efficiency (86%) was achieved with an irrigation regimen of 50-ml applications with at least 40 min between applications, compared to 62% for the control treatment (a single, continuous application of 600 ml). Our results suggest that growers using spray stakes would waste less water by applying water intermittently rather than continuously.
Container nurseries often irrigate daily with a fixed amount of water that exceeds the water-holding capacity of the container substrate, thus, leaching a portion of the applied water and nutrients. We compared the influence of daily container irrigation based on substrate moisture tension (SMT) to that of daily irrigation with a set amount on irrigation volume, container effluent volume, total effluent N content, and plant growth. Rhododendron, Ilex, and Juniperus were grown outdoors in 11.3-L containers in a pine bark-based substrate at four rates of fertilization with a controlled-release fertilizer. Drip irrigation was applied each morning until an electronic tensiometer signaled an irrigation controller that SMT was less than a set value corresponding to container capacity. Irrigation at 1.5 cm·d–1 served as the control. Irrigation treatment had little influence on growth and no influence on growth response to fertilizer rate. Irrigation volume, effluent volume, and total effluent N content were lower for each species when irrigation was based on SMT. For Juniperus, irrigation volume, effluent volume, and total effluent N content were 62%, 69%, and 60% less, respectively, for tension-based irrigation than for irrigation with a set amount.
Determination of water needed for good function of established groundcovers in the Southwest is important in creating well-adapted, sustainable urban landscapes in this semi-arid region. Myoporum parvifolium from Australia and Dalea greggi from the Chihuahua Desert were tested at 100%, 75%, 50% and 25% of evaporation from an adjacent class A pan. Myoporum grew most at the higher irrigation regimes, but actually performed best at the lowest irrigation level, growing less than those given more water, but showing better color and vigor. Infrared leaf temperature data showed that lowest irrigation regime plants still transpired actively and had cool leaves. With Dalea, growth was directly related to water applied, with the most growth at the 100% treatment. All plants survived, but the lowest irrigation regime plants were sparse and showed definite signs of water stress. Infrared temperature measurements indicated increasing water stress as water applied decreased. At treatment onset, the Dalea had not completely covered the soil surface, so 75% of pan evaporation can be considered adequate for establishment of Dalea.
A survey to determine teaching methodologies for plant material courses was conducted. A total of 120 surveys was sent to horticulture programs at U.S. universities and colleges. Thirty-nine, 22, and 8 respondents taught a woody plant (W), a herbaceous perennial (HP)/annual (A) course, and a foliage plant course, respectively; 21 respondents taught a combination of theses courses. The following similarities were noted for W and HP/A: 1) about 190 species per Semester were presented usually in a taxonomic order using slides as the primary teaching medium for lecture, 2) the most common student complaint was too much work and memorization, 3) the most common student compliment was the practical and useful nature of the subject matter, 4) in order of importance, plant identification, landscape value, and plant cultural aspects were emphasized. For W and HP/A, 93% and 65% of plants, respectively, were presented as landscape and arboreta specimens. Seventy percent of W courses used Dirr's Manual of Woody Landscape Plants; 58% and 10% of HP/A courses used Still's Manual of Herbaceous Ornamental Plants and Taylor's Guides, respectively.
More regulations have an impact on nursery industry today than 10 to 20 years ago, and additional regulations are likely in the future. In view of this, the southeastern nursery industry is taking proactive action by developing a handbook of irrigation and fertilization best management practices (BMP) for container nurseries. Using BMP would be voluntary but could “head off” additional regulations. Additionally, BMP would serve as guidelines for growers 1) attempting to be more environmentally friendly, 2) wanting to promote the fact they are environmentally friendly, and 3) dealing with a complaint from regulatory agencies. Our objective was to develop a BMP handbook that nursery managers could use to find answers quickly to management questions regarding irrigation and fertilization. The handbook was written by university horticulturists, but input and reviews were obtained from industry personnel, additional university personnel, and others associated with the nursery industry. The handbook will be distributed in late summer by the Southern Nurserymen's Association, Marietta, Ga.
Two experiments were conducted to test the effects of early root pruning on growth of pin oak (Quercus palustris Muenchh.). Experiment one tested the effect of radicle tip removal when radicles had reached 5, 10, or 15 cm below the substrate surface. Total root length was not affected by treatment, but root-pruned trees had more large-diameter lateral (primary lateral) roots than trees that were not root-pruned. The number of primary laterals increased if the radicle tip was removed at more shallow depths. Experiment two tested the effect of liner production in bottomless containers (roots air-pruned) of 5-, 10-, 15-, and 20-cm depths on subsequent growth in #2 (6-L) containers. Top and root growth was generally lowest in 5-cm-deep containers and highest in 10- or 15-cm-deep containers.
Pine bark (PB), either unamended or amended with sand (S) at 9 PB: 1 S or 5 PB:1 S (v/v), was fertilized with solutions of 100,200, or 300 mg N/liter solution and tested for N concentration using the pour-through method (PT). PB, 9 PB: 1 S, and 5 PB: 1 S had porosities of 84%, 75%, and 66%, respectively. PT NO3-N concentrations, obtained via PT, of the 5 PB:1 S substrate were 43%,28%, and 15% higher than PB NO3-N values for the 100,200, and 300 mg·liter-1 treatments, respectively. Differences in N concentration obtained with PT can be attributed to substrate physical characteristics. Based on the results, data for PT should be interpreted with regard to substrate porosity.
Maximizing nutrient use efficiency while minimizing nutrient leaching and non-point source contributions from containerized crop production systems are goals of researchers and growers. These goals have led to irrigation and crop nutrition management practices that reduce fertilizer and irrigation expenditures and reduce the nutrient load into the environment. However, one area that has received little attention, and may lead to the further refinement of crop management practices, is how dissolved nutrients (solutes) move through a substrate while water is being applied during irrigation. A study was conducted to characterize the effect of a controlled-release fertilizer (CRF) placement method on changes in leachate nutrient concentration throughout an irrigation event and to evaluate these changes at different times throughout a production season. A pine bark:sand (9:1, by volume) substrate was placed in 2.7-L nursery containers (fallow) and was treated with topdressed, incorporated, and dibbled CRF or did not receive CRF. The nutrient leaching pattern was evaluated at 3, 9, and 15 weeks after potting (WAP). Leachate nutrient concentration was the highest in the first 50 mL of effluent and steadily diminished as irrigation continued for the topdressed, incorporated, and the no CRF treatments. Effluent nutrient concentration from containers with dibbled CRF generally increased throughout the first 150 mL of effluent, plateaued briefly, and then diminished. The nutrient load that leached with higher volumes of irrigation water was similar between incorporated and dibbled CRF placements. However, the unique nutrient leaching pattern observed with the dibbled CRF placement method allowed for a lower effluent nutrient load when leaching fractions are low. Dibble may be an advantageous CRF placement method that allows for the conservation of expensive fertilizer resources and mitigates non-point source nutrient contributions by reducing undesired nutrient leaching during irrigation.