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- Author or Editor: T. H. Yeager x
Polyvinyl chloride columns (4 × 15 cm) containing by volume either 2 pine bark : 1 moss peat : 0 sand, 2 pine bark : 0 moss peat : 1 sand, 0 pine bark : 1 moss peat : 1 sand, or 2 pine bark : 1 moss peat : 1 sand amended with 3 kg m-3 of 32P-superphosphate (8.7% P) were leached daily with 16 or 32 ml of deionized water (pH 5.5) in 1 hour. Irrigation rate did not affect 32P leaching nor was there a media rate interaction or difference in the percentage total 32P and dissolved 32P leached. Medium 2:1:1 had the greatest percentage (76%) of 32P leached during the 3-week experimental period, however, 55% of the 32P amendment leached from each medium the 1st week.
A goal of irrigation best management practices in container nurseries is to conserve water while maintaining optimal plant growth and quality. A web-based, container irrigation management program (CIRRIG) was developed to automatically provide daily irrigation run times for sprinkler-irrigated crops in container nurseries. The program estimates evapotranspiration rates based on weather uploaded from a weather station located on-site and plant production conditions monitored in each zone and adjusts irrigation run times based on irrigation application rate, the plant’s irrigation-capturing ability (for sprinkler irrigation), desired leaching fraction, and irrigation system uniformity. For this project we interfaced CIRRIG output with a programmable logic controller (PLC) to automatically irrigate a sprinkler-irrigated crop at a container nursery in Florida. Sweet viburnum (Viburnum odoratissimum) in 10-inch-diameter containers were grown by the nursery for 24 weeks in adjacent irrigation zones, one controlled automatically using CIRRIG and the other by the nursery’s traditional practice of manually turning on and off irrigation. Water use was monitored with flowmeters and plant growth by measuring plant size and shoot dry weight periodically throughout the trial. Plant growth was not different (P < 0.05) because of irrigation practice. CIRRIG reduced water use during the study period by 21% (42 vs. 53 inches) compared with the nursery’s irrigation practice. An assessment of the water-saving benefits of making daily adjustments to irrigation run times based on weather including rain indicated savings of 25% and 40% compared with biweekly adjustments with and without automatic rain cutoff, respectively. This trial demonstrated that CIRRIG coupled with an on-site weather station and a computer-controlled irrigation system can be used to manage irrigation while conserving water in a container nursery.
Higher N rates applied to Ilex crenata‘ Helleri’ holly liners grown in the greenhouse increased shoot growth but-decreased root growth resulting in a greater shoot:root ratio. Higher N rates reduced the time required for a shoot growth flush to occur. Ρ at 85-500 ppm had no effect on shoot or root growth. Continued growth of liners at 50 ppm N lowered the shoot:root ratio due to stimulation of root growth while 300 ppm N caused the shoot:root ratio to increase due to increased shoot growth.
Incorporation of superphosphate into a pine bark growing medium did not increase growth of ‘Hellen’ holly if the plants were subsequently fertilized with slow-release granular or a water soluble fertilizer. Tissue P levels, except for the water soluble fertilizer treatment, and medium P levels were higher as a result of superphosphate incorporation.
Greenhouse-grown branched liners of ‘Helleri’ holly were fertilized with either 0, 5, 10, 15, 20, 25, or 30 ppm P to establish a P level in the pine bark medium that resulted in maximum shoot dry weight. Pine bark P levels greater than 10 ppm did not result in increased shoot dry weight. Total mg of P in shoot tissues continued to increase with P treatments higher than 10 ppm, indicating luxury consumption of P. Total mg of P in root tissues increased to the 5 ppm P treatment. Total μg of Mn in shoot tissues increased while total pg of Mn in root tissues decreased with increasing pine bark P levels. In a subsequent experiment, dry shoot weights of ‘Helleri’ holly grown in a pine bark medium amended with either 270, 540, or 810 g/m3 of P supplied as superphosphate (9% P) or fertilized with 10 ppm P were not different, while root dry weights decreased with increasing P amendment. Water extractable P for the 810 g/m3 treatment decreased 245 ppm during the experiment and by week 5 was below 10 ppm.
Photinia ×fraseri Dress and Podocarpus macrophyllus (Thunb.) D. Don were grown in a Metro-Mix 500 medium amended with 0.0%,0.25%,0.5%,0.75%, or 1.0% (by volume) of a K-based hydrophilic polymer and were irrigated every 3,6,9, or 12 days with a solution that contained either 100, 200, 300, or 400 mg N/liter, respectively: Photinia ×fraseri plants irrigated every 6 days with 200 mg N/liter in irrigation water and grown in 0.75 % polymer-amended medium had higher root and shoot dry weights (6.3 and 28 g, respectively) after 144 days than plants grown in the unamended medium (3.4 and 17 g, respectively). Shoot dry weights of P. macrophyllus grown 192 days in the amended medium were similar to those of plants grown in the unamended medium. Average shoot dry weights increased from 10 to 18 g, respectively, as number of irrigations increased from every 12 days with 400 mg N/liter in irrigation water to every 3 days with 100 mg N/liter in irrigation water. Podocarpus macrophyllus root dry weights were 1.9 and 3.6 g for plants irrigated every 12 and 3 days, respectively, while plants grown in the unamended medium had the highest root dry weight (3.2 g). Data from this study indicated that growth response to a cross-linked, K polyacrylate/polyacrylamide, hydrophilic polymer-amended Metro-Mix 500 medium varied with species and number of irrigation and concomitant fertilizer applications.
Rooted cuttings of Photinia X fraseri and Podocarpus macrophyllus were grown in Metro-mix 500 amended with 0.0, 0.25, 0.50, 0.75, or 1.0% (w/w) Stockosorb 300, a K-based superabsorbent polymer. All 3-liter containers were irrigated with 500 ml of 100, 200, 300, or 400 ppm 20N-8.7P-16.72K Peters fertilizer solution once every 3, 6, 9, or 12 days, respectively. In comparison with the unamended media, P. X fraseri had equal or better growth (shoot and root fresh and dry weights, increased height, and branch and leaf numbers) with 3, 6, and 9 day irrigation in all but the 1 % amended medium. Growth of P. macrophyllus was not noticeably affected by the polymer amendment. This is not unexpected since P. X fraseri is a broad-leaf plant while P. macrophyllus is a slow growing, narrow-leaf conifer. Nitrogen, P, and K tissue levels for Photinia and Podocarpus decreased for the 12 day irrigation treatment regardless of amendment rate. Except for Fe, which was highest at nine day irrigation intervals, micronutrients remained more or less constant in both species. The amended media had a greater water holding capacity at termination of the project (144 and 192 days for Photinia and Podocarpus, respectively) than at the start. Thus, K-based superabsorbents may be used successfully to reduce irrigation frequency.
Multiple branched liners of ‘Helleri’ holly growing in a pine bark medium were fertilized at the beginning of active root growth at 300, 400, 500, or 600 ppm N with a 20N−8.7P−16.7K water soluble fertilizer. One week later, one half of the plants were fertilized again. The treatments were repeated during the next 2 periods of root growth which occurred about 6 weeks apart. The above soluble fertilizer was applied weekly at 300 ppm N to the control plants. Shoot growth of plants fertilized twice at 500 ppm N was comparable to growth of the control plants. Further, these plants received 44% less fertilizer and utilized 17.6% more of the total fertilizer applied. Extract nutrient and soluble salt levels were high during root growth and low during shoot growth except for the control plants, indicating the plant's need for fertilizer predominates during periods of active root growth.
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.
Pine bark was shown to adsorb 1.5 mg of N/g of bark when NH4 solutions were leached through the bark. Increasing pH of bark increased adsorbed NH4. At pH 3.3, only NH4 was adsorbed to bark particles when a fertilizer solution containing NH4, Ca, K, and Mg was applied. However, adsorption of NH4 and other cations increased as pH was increased from 3.8 to 5.8. These data indicate that 2 types of sites exist for the adsorption of NH4 to pine bark. One site is effective at lower pH; the other is active as pH increases. Daily application of 2.5 cm of water containing 50 ppm NH4 required 20 days for equilibration to occur so as to satisfy all binding sites. Thus, incorporation of NH4 into a pine-bark medium prior to planting may be advisable to prevent low N levels from occurring in the container solution due to NH4 binding when plants are first planted and fertilized.