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  • Author or Editor: Thomas Yeager x
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Fabric containers (FAB), due to their root-pruning properties, can be used as an alternative to conventional plastic containers (PLA) in container nurseries. Because sidewall evaporation in FAB has been shown to reduce container substrate temperatures, our objective was to determine if FAB would reduce the release rate of controlled-release fertilizer (CRF), resulting in less leachate loss of nitrogen (N) and phosphorus (P) and greater CRF longevity. Dwarf Burford holly were grown in 36-cm-diameter (18-L substrate) FAB or PLA in a bark-peat substrate with incorporated CRF. Spray stake irrigation was routinely adjusted to a target leaching fraction of 25%. Maximum daily substrate temperature, measured 3 cm from southwest-facing container wall, averaged 6 °C lower in FAB than in PLA. For two 31-week experiments where leachate was continuously collected and sampled weekly, FAB reduced leachate N loss by 30% and P loss by 47% despite requiring 66% more irrigation water and collecting 31% more leachate than with PLA. FAB reduced average N loss from 114 to 78 kg·ha−1 and average P loss from 16.0 to 8.6 kg·ha−1. FAB increased plant size by 8% and shoot dry weight by 12% for one experiment but had no effect in the other. We concluded that compared with PLA, the use of FAB can decrease leachate loss of N and P but require considerably more irrigation water to offset water loss via sidewall evaporation.

Open Access

Irrigation scheduling in container nurseries is challenging due to the wide range of plant production conditions that must be accounted for at any given time. An irrigation scheduling system should also consider weather affecting evapotranspiration to apply proper amounts of water that will ensure optimal growth with minimal runoff (container drainage). We developed an automated system that relies on routine leaching fraction (leachate/water applied) testing and real-time weather recorded on-site to make adjustments to irrigation. A web-based program (CIRRIG) manages irrigation zone inputs [weather and leaching fraction (LF) test results] and outputs irrigation run times that can be implemented automatically with programmable logic controllers. In this study conducted at a nursery in central Florida, we compared the automated technology (CIRRIG) with the nursery’s traditional irrigation practice (TIP) of manually adjusting irrigation based on substrate moisture status of core samples taken twice weekly. Compared with TIP, CIRRIG reduced water use in six of seven unreplicated trials with water savings being greater for microirrigated crops grown in large containers than for sprinkler-irrigated crops in small containers. Reduced pumping cost associated with water savings by CIRRIG was estimated to be $3250 per year, which was insignificant compared with the labor savings of $35,000 to $40,000 anticipated by the nursery using CIRRIG in lieu of TIP. At the end of the project, the necessary hardware was installed to expand CIRRIG nursery-wide and control 156 zones of irrigation.

Open Access

Abstract

Lateral root pruning and rootstock undercutting is practiced in field tree production. The timing, frequency, pruning distance from the trunk, and depth of pruning vary within the industry. Lateral roots formed in response to pruning usually originate close to the cut surface (1, 2, 5). Two recent studies indicated that root pruning field-grown landscape-sized trees increased root density within the root ball (3, 4). This research was conducted to determine the effect of root pruning on the location of regenerated roots and growth of existing unpruned lateral roots.

Open Access

Rain drop momentum, based on the height from which it falls, is an important factor in drop penetration of plant canopy. This may explain why nursery operators report that substrates appear wetter from rain than from an equivalent amount of water applied with overhead irrigation. We investigated the influence of irrigation nozzle height on amount of water captured by Rhododendron sp. `Formosa' grown in 10-liter containers. A Wobbler® (#8, 7.6 liters·min–1) irrigation nozzle was positioned 1.2, 2.4, 3.6, 4.8, or 6.0 m above grade. Plants were placed in a circle 3.6 m from the riser base for the 1.2-m-high nozzle, 4.5 m from riser base for the 2.4-m-high nozzle, and 5.4 m from riser base for all other heights and irrigated for 3 hours. Preweighed disposable diapers were placed on substrate surface of each container with and without (control) plants. Diapers were weighed after irrigation and water captured was calculated and expressed as percentage of control containers. Capture increased from 144% at 1.2 m to 178% at 3.6 m then declined with increasing height. The decline was likely due to small drops with low momentum striking plants because plants remained 5.4 m from the riser base.

Free access

Columns (4 × 15 cm) of a pine bark medium amended with the equivalent of 4.2 kg per cubic meter of dolomitic limestone and either 0, 2.4, 4.7, 7.1 or 9.5 mg of urea-formaldehyde (38% N) per cubic centimeter of medium were leached daily with 16 ml of deionized water (pH 5.5). Leachate total N, NO3 --N and NH4 +-N concentrations were determined on day 1, 3, 5, 7, 14, 28, 49, 91, 133, 203, 273 and 343. Leachate total N ranged from 600 ppm on day 1 for the 9.5 mg treatment to 4 ppm on day 273 for the 2.4 mg treatment. Leachate NH4 +-N concentrations ranged from 38 ppm c4 day 3 for the 9.5 mg treatment to less than 1 ppm on day 7 for the 2.4 mg treatment and were less than total N concentrations at each sampling time. Leachate NO3 --N was not detectable during the experimental period. Eleven, 16, 20 and 25% of the applied N leached from the columns amended with 2.4, 4.7, 7.1 or 9.5 mg of urea-formaldehyde per cubic centimeter of pine bark, respectively, during the 371 day experiment.

Free access

Nitrogen fertilizer rates are often expressed as lb N/A. However, without explanation of the actual area fertilized, exact rates cannot be duplicated because the rate may be given in terms of an acre equivalent. For example, 100 lb N/A for turf implies that 100 lb of N was applied on 43,560 sq ft or real estate acre (R.E.A.). The same rate applied to row crops where the actual area fertilized consists of bands that total 0.05 of a R.E.A., means that 20 times the amount of fertilizer was applied per sq ft even though the rate was reported as 100 lb of N/A and 100 lb of N were actually applied. Fertilization of trees in a field nursery is similar in concept, but what does a rate of 100 lb of N/A mean? If the area fertilized around the trees was 0.05 of a R.E.A., it is not clear whether 0.002 lb N/sq ft or 0.04 lb N/sq ft was applied. If 0.002 lb N/sq ft was applied, then 5 lb of N would have been applied on 0.05 of a R.E.A., thus the rate was given as 100 lb N/A equivalent. To avoid confusion, area fertilized per plant or tree, amount per unit area, number of applications per year and number of plants per R.E.A. are needed to actually calculate the amount of N applied per year per R.E.A.

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Marketable size plants of sweet viburnum (Viburnum odoratissimum Ker-Gawl.), waxleaf ligustrum (Ligustrum japonicum Thunb.), and azalea (Rhododendron spp. L. `Southern Charm') grown in 11.4-L containers were irrigated with overhead impact sprinklers at container spacings ranging from 0 to 51 cm apart. Water reaching the substrate surface was quantified and the percentage of that applied calculated as percent capture (% capture). Percent capture is defined as the percentage of water falling above the plant within a projected vertical cylinder of a container that reaches the substrate surface. For all species, % capture increased linearly with the decline in adjacent canopy interaction, which results from canopies extending beyond the diameter of a container. Increases in total leaf area or leaf area outside the cylinder of a container, in conjunction with increasing distance between containers, were significantly (P < 0.05) correlated with increases in % capture for ligustrum and viburnum. Increases in % capture partially compensated for decreases in percentage of production area occupied by viburnum containers as distances between containers increased, but not for the other two species. Under commercial conditions, optimal irrigation efficiency would be achieved when plants are grown at the minimum spacing required for commercial quality. This spacing should not extend beyond the point where canopies become isolated.

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Columns (4 × 15 cm) of incubated (25C, 7% volumetric moisture) milled cypress [Taxodium distichum (L.) L. Rich] wood chips received 180 mg of each ionic form of N applied to the surface from dry NH4NO3, KNO3, or (NH4)2SO4 and were leached daily with 16 ml deionized water (pH 5.5). After 10 days, >85% of applied N leached from the columns in all treatments. After 25 days, all N leached from the NH4NO3 and KNO3 treatments, and 93% leached from the (NH4)2SO4 treatment. In subsequent experiments, columns received 360 mg N from NH4NO3 and were leached daily with either 16, 32, 48, or 64 ml of deionized water for 50 days. The rate of N leaching increased with increasing water application rate, although total N leached per column was similar for all water rates after 25 days. Columns that received 45, 90, 180, or 360 mg N/column were leached daily with 16 ml of deionized water. Nitrogen concentrations in the leachate ranged from 3406 ppm NO 3 -N and 2965 ppm NH 4 + -N at day 5 for the 360-mg rate to 3 and 5 ppm, respectively, at day 35 for the 45-mg rate. In all experiments with NH4NO3, more NO 3 -N leached than NH 4 + -N and more NO 3 -N leached than applied, indicating vitrification occurred. NH 4 + -N and NO 3 broadcast over cypress wood chips in the landscape would leach quickly into the soil.

Free access

Ilex crenata Thunb. `Rotundifolia' grown in sand culture with the root zone at 40C for 6 hours daily had smaller root and shoot dry weights after 6 weeks than plants grown with root zones at 28 or 34C. Root and shoot N accumulation (milligrams N per gram of dry weight) decreased when root-zone temperatures were increased from 28 to 40C and plants were fertilized twice dally with either 75, 150, or 225 mg N/liter. Nitrogen application rates of 150 or 225 mg·liter-1 resulted in increased root and shoot N accumulation for plants grown with root zones at either 28, 34, or 40C compared with the 75 mg N/liter treatment. Increased N fertilization rates did not alleviate reduced plant growth due to the high root-zone temperature.

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The influence of production practices on runoff from container nurseries was investigated in Spring 2003 (March to July) and Fall 2003 (August to January). Viburnum odoratissimum (Ker-Gawl.) liners were planted in 3.8-L containers with a 2 pine bark: 1 sand: 1 Canadian peat substrate and placed on 1.5 m2-platforms at one of two plant spacing densities: 16 or 32 plants/m2 [spaced to 16 plants/m2 after 13 weeks (spring) or 14 weeks (fall)]. Overhead sprinkler irrigation was applied daily (1 cm) and runoff collected weekly. Osmocote 18 N-2.6 P-10 K was surface-applied to each container (15 g) in the spring and surface-applied or incorporated in the fall. Cumulative runoff averaged 1240 L·m-1; in spring (19 weeks) and 1050 L·m-1; in fall (20 weeks), which represented 72% and 66% of applied irrigation plus rainfall, respectively. The lower density spacing resulted in a 19% increase in cumulative runoff in spring (1340 vs. 1130 L·m-1) but had no effect in fall (970 vs. 890 L·m-1). Weighted average ECwa of runoff decreased 10% (0.436 vs. 0.485 dS·m-1) and 12% (0.420 vs. 0.476 dS·m-1) with the lower density spacing in spring and fall, respectively. ECwa in fall was not affected by fertilizer method. Plant size index [(height + width)/2] was reduced 22% in both spring (38.7 vs. 49.7 cm) and fall (26.9 vs. 34.4 cm) when plants were grown at the lower density spacing throughout production. This reduction in plant size was attributed to container heat stress. Plant size was unaffected by fertilizer application method (fall) but fertilizer incorporation resulted in greener plants than surface-applied fertilizer (60 vs. 53 SPAD readings).

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