Search Results

You are looking at 1 - 10 of 11 items for

  • Author or Editor: Bert M. Cregg x
Clear All Modify Search
Free access

Pascal Nzokou and Bert M. Cregg

Growth and nutrient uptake of containerized fraser fir (Abies fraseri) seedlings in response to irrigation and fertilization was investigated for 2 years in a greenhouse experiment. Height and stem diameter growth increased 12% to 35% and 4% to 32%, respectively, with increased irrigation. There was an inverse relationship between irrigation and foliar nitrogen content and no irrigation effect on foliar phosphorus, potassium, magnesium, and manganese. Irrigation increased foliar calcium. Approximately 2.0% to 4.5% of applied nitrogen was lost through leaching. Increases in total biomass in high irrigation treatments were caused by higher root and stem biomass. Higher irrigation treatments increased nitrogen use efficiency (NUE) and assimilatory nitrogen use efficiency probably as a result of increase in carbon assimilation efficiency leading to increase in net primary productivity. There was no clear effect on the root weight ratio, but the index nitrogen availability per unit of foliage indicated a higher availability in plants receiving the lowest irrigation. This suggests that under water stress, the decrease in assimilation and NUE may be buffered by an increase in the plant's ability to provide nitrogen and other nutrients to various organs.

Free access

Bert M. Cregg and Robert Schutzki

Landscape mulches are widely promoted to improve soil moisture retention, suppress weeds, and improve the growth of landscape plants. The objective of this project was to determine the effect of common landscape mulches (pine bark, hardwood fines, cypress mulch, color-enhanced ground pallets) on soil moisture, soil pH, weed control, and physiology and growth of landscape shrubs. Two additional treatments were not mulched: no mulch + no weed control and no mulch + weed control. Growth was measured on eight taxa (Euonymus alatus ‘Compactus’, Spiraea ×bumalda ‘Goldflame’, Weigela florida ‘Java red’, Taxus ×media ‘Runyan’, Thuja occidentalis ‘Golden Globe’, Hydrangea paniculata ‘Tardiva’, Viburnum dentatum ‘Synnestvedt’, Viburnum trilobum ‘Compactum’). Leaf gas exchange [net photosynthesis and stomatal conductance (g s)] were measured on Hydrangea paniculata, V. dentatum, and V. trilobum only. All mulches increased soil moisture compared with no mulch + weed control. There was no difference in soil pH or foliar nitrogen among treatments. All mulches, except cypress mulch, increased plant growth of most shrub taxa compared with no mulch without weed control. Mulches increased g S relative to no mulch without weed control. Photosynthetic rates of plants mulched with cypress mulch were less than the other mulches and not different from no mulch. Overall, the result suggests that, except for cypress mulch, the organic mulches tested are equally effective in improving growth of landscape plants. Reduced photosynthetic efficiency and growth of shrubs with cypress mulch suggest potential allelopathic effects.

Free access

Bert M. Cregg, Pascal Nzokou and Ron Goldy

We evaluated height growth, diameter growth, and survival of newly planted fraser fir and colorado blue spruce Christmas trees in southwest Michigan in response to mulch, weed control, and irrigation. Mulches included black polyethylene, white polyethylene, VisPore mulch mats, and wood chips. Seedlings were also established with or without raised beds and with or without complete weed control. Weed control (mulches or a combination of chemical weed control and hand weeding) improved survival and growth of both species after 2 years. Growth was similar for trees in irrigated plots or with wood chip mulch without irrigation. Polyethylene mulch increased growth compared with similar production systems with raised beds and bare ground. Among production systems, variation in growth and survival reflected patterns of predawn water potential and midday shoot gas exchange, suggesting that differences were largely related to plant moisture stress. White mulch improved growth relative to similar production systems with black mulch and wood chip mulch improved growth compared with similar production systems without irrigation. Overall, the ranking of magnitude of growth response effects were weed control > irrigation > mulch. These results underscore the importance of weed control for establishment and maintenance of high-quality Christmas tree plantations.

Full access

N.J. Gooch, Pascal Nzokou and Bert M. Cregg

Containerized conifers are increasingly marketed and used as live Christmas trees worldwide. However, prolonged exposure to indoor conditions may reduce cold hardiness. We examined physiological and morphological changes of three species black hills spruce (Picea glauca), balsam fir (Abies balsamea), and douglas fir (Pseudotsuga menziesii var. glauca) subjected to in-home conditions for 10 and 20 days. Shoot cuttings were subjected to artificial freeze testing (AFT) and the physiological and morphological changes were evaluated by chlorophyll fluorescence, bud mortality, and needle damage. After 7 days indoors, bud temperature at 50% lethality (LT50) was −24.5 °C for douglas fir, −23.5 °C for black hills spruce, and −22.5 °C for balsam fir. After 20 days indoors, bud LT50 increased to −18 °C for black hills spruce and balsam fir, and −21 °C for douglas fir. The effect of the indoors exposure on needle damage was very limited for black hills spruce and balsam fir; however, severe needle damage was apparent on douglas fir even at just 3 days of indoor exposure (LT50 = −21 °C). This negative impact worsened with indoor exposure time with LT50 for after 20 days of indoor exposure at −7 °C. Chlorophyll fluorescence values followed a similar trend with needle damage with black hills spruce and balsam fir showing no difference, while douglas fir values were significantly affected. These results confirm the hypothesis that live trees kept indoors for extended periods progressively deharden and become very sensitive to cold damage when moved outdoors following the indoor exposure. However, whole plant survival after transplantation in the field did not corroborate results obtained from the AFT. Further studies are needed to investigate the potential causes of the high transplantation mortality following the display treatments.

Full access

Pascal Nzokou, Nicholas J. Gooch and Bert M. Cregg

Irrigation of fraser fir (Abies fraseri) in Christmas tree production is gaining importance in the upper midwestern United States because of the intensive planting of this species out of its natural range. However, current scheduling practices rely on empirical observations with no monitoring of soil moisture and no use of automated irrigation system. The goal of this project was to design, construct, and implement a tensiometer-based automated irrigation system for fraser fir Christmas tree plantations that would (1) use existing technologies, (2) apply water based on changes in soil moisture content, (3) provide operational flexibility, and (4) interface with a computer for system changes, data collection, and system modifications. Soil tensiometers equipped with 4- to 20-milliampere transducers were installed at two drip-irrigated tree farms. Water on demand was controlled by soil moisture tension levels that triggered the stimulation of a relay wired to solenoids delivering irrigation water to the various treatments. The system functioned according to the design as expected. However, several issues associated with the need for regular maintenance of tensiometers, computer programming, and system wiring created some challenges regarding the reliability and transferability of similar system to commercial facilities.

Open access

Shital Poudyal and Bert M. Cregg

Interest in capturing and reusing runoff from irrigation and rainfall in container nurseries is increasing due to water scarcity and water use regulations. However, grower concerns related to contaminants in runoff water and other issues related to water safety are potential barriers to the adoption of water capture and reuse technologies. In this review, we discuss some of the key concerns associated with potential phytotoxicity from irrigating container nursery crops with recycled runoff. The concentration of pesticides in runoff water and retention ponds is orders of magnitude lower than that of typical crop application rates; therefore, the risk of pesticide phytotoxicity from irrigation with runoff water is relatively low. Nonetheless, some pesticides, particularly certain herbicides and insecticides, can potentially affect crops due to prolonged chronic exposure. Pesticides with high solubility, low organic adsorption coefficients, and long persistence have the greatest potential for crop impact because they are the most likely to be transported with runoff from container pads. The potential impact on plant growth or disruption of physiological processes differs among pesticides and sensitivity of individual crop plants. Growers can reduce risks associated with residual pesticides in recycled irrigation water by adopting best management practices (e.g., managing irrigation to reduce pesticide runoff, reducing pots spacing during pesticide application, use of vegetative filter strips) that reduce the contaminant load reaching containment basins as well as adopting remediation strategies that can reduce pesticide concentrations in recycled water.

Free access

Wendy S. Klooster, Bert M. Cregg, R. Thomas Fernandez and Pascal Nzokou

Container production of landscape conifers, including pot-in-pot (PIP) production, is increasing relative to field production in the northern United States. Because much of the research on PIP has been performed in the southern United States, this study focused on characterizing the growth and physiological response of PIP-grown conifers to fertilizer and substrate to improve production for growers in northern climates. In May 2006, we potted 90 seedlings each of Abies fraseri, Picea glauca var. densata, P. pungens glauca, and Pinus strobus into 11.2-L containers. Substrate consisted of pine bark (B) and peatmoss (PM) in ratios of 90:10, 80:20 or 70:30 (vB:vPM). Trees were top-dressed with controlled-release fertilizer (15N–4P–10K) at rates of 0.25, 0.5, and 1.0 g of nitrogen per liter of container (g·L−1). After 2 years, growth response to substrate varied by species; however, all species grew as well or better in the 80:20 mix than in the other mixes. In response to fertilizer addition, adding 0.5 or 1 g N/L increased height growth compared with 0.25 g. Increasing the fertilizer rate from 0.5 g N/L to 1 g did not increase height growth. Foliar nitrogen increased with each fertilizer addition although height growth did not increase beyond 0.5 g·L−1, indicating possible luxury consumption. Furthermore, net photosynthesis rates of spruce trees declined with fertilization in the second year of the study, possibly as a result of increased water stress due to greater total leaf area per tree. Chlorophyll fluorescence was not consistently correlated with foliar nutrition. From a practical standpoint, results of the study indicate that 0.5 g N/L will provide adequate nutrition for these crops. A substrate mix of 80% bark:20% peatmoss produced maximal or near-maximal growth for all four species tested.

Free access

Aaron L. Warsaw, R. Thomas Fernandez, Bert M. Cregg and Jeffrey A. Andresen

Irrigation scheduling based on plant daily water use (DWU) to conserve water without adversely affecting plant growth compared with a traditional irrigation rate was investigated for 25 common container-grown woody ornamentals. Ten different taxa were grown in 2006 and 2007 and five in 2008 in 10.2-L (No. 3) containers. Overhead irrigation was applied in four treatments: 1) a control irrigation rate of 19 mm (1.07 L per container) per application (control); 2) irrigation scheduled to replace 100% DWU per application (100DWU); 3) irrigation alternating every other application with 100% replacement of DWU and 75% DWU (100-75); and 4) irrigation scheduled on a three application cycle replacing 100% DWU followed by two applications of 75% DWU (100-75-75). Irrigation applications were separated by at least 24 h. Daily water use was calculated by measuring the difference in volumetric moisture content 1 h and approximately 24 h after irrigation. The three DWU treatments reduced total irrigation applied 6% to 75% compared with the control depending on treatment and species, except for Buddleja davidii ‘Guinevere’ in which total irrigation applied by the 100DWU, 100-75, and 100-75-75 treatments was 26%, 10%, and 5%, respectively, greater than the amount applied to the control. Final growth index [(plant height + width A + width B)/3] of all DWU treatments was greater than or equal to the control for all taxa. Forsythia ×intermedia ‘New Hampshire Gold’, Hydrangea arborescens ‘Dardom’, Hydrangea paniculata ‘Unique’, and Weigela florida ‘Wilma’ had higher water use efficiencies (estimated as the change in growth index per liter of water applied) at lower irrigation treatment volumes with no differences in growth index or growth index increase, indicating that further irrigation reductions may be possible without affecting growth. PourThru electrical conductivity of H. arborescens ‘Dardom’, Spiraea fritschiana ‘Wilma’, and Viburnum ×burkwoodii ‘Chenaultii’ measured in 2007 did not accumulate to damaging levels. Final plant size of all taxa under DWU treatments was the same or greater than the control and substantially less water was applied under DWU treatments except for B. davidii ‘Guinevere’.

Free access

Nicholas A. Pershey, Bert M. Cregg, Jeffrey A. Andresen and R. Thomas Fernandez

The objectives of this study were to quantify irrigation volume, runoff volume and nutrient content, and plant growth of container-grown conifers when irrigated based on plant daily water use (DWU) vs. a standard irrigation rate. Four conifer taxa were grown in 10.2-L (no. 3) containers subjected to four irrigation treatments from 23 June to 16 Oct. 2009 and 6 June to 31 Oct. 2010. The taxa were: 1) Chamaecyparis obtusa Sieb. & Zucc. ‘Filicoides’, 2) Chamaecyparis pisifera (Sieb. & Zucc.) Endl. ‘Sungold’, 3) Thuja occidentalis L. ‘Holmstrup’, and 4) Thuja plicata D. Donn ‘Zebrina’. The four irrigation treatments were: 1) control application of 19 mm·d−1, 2) irrigation applied to replace 100% DWU (100 DWU) per day, 3) applications alternating 100% with 75% DWU in a 2-day cycle (100–75 DWU), and 4) a 3-day application cycle replacing 100% DWU the first day and 75% DWU on the second and third days (100–75–75 DWU). Irrigation treatments did not affect plant growth index {GI= [(H + WNS + WEW)/3]} in 2009. In 2010, GI of C. obtusa ‘Filicoides’ was greater for 100 DWU than the control plants. Seasonal total water applied for 100, 100–75, and 100–75–75 DWU was 22%, 32%, and 56% less, respectively, than the control amount of 117 L per container in 2009 (114 days) and 24%, 18%, and 24% less than the control amount of 165 L per container in 2010 (147 days). Scheduling irrigation based on DWU reduced runoff volumes and (nitrate-nitrogen) NO3 -N and (phosphate-phosphorous) PO4 3−-P load compared with the control. Irrigating based on DWU reduced water application and runoff volumes and NO3 -N and PO4 3−-P load while producing plants of equal or greater size than control plants.

Free access

Bridget K. Behe, Rachel M. Walden, Marcus W. Duck, Bert M. Cregg, Kathleen M. Kelley and R.D. Lineberger

An aging American population may be less willing than a younger population to install and remove a live, fresh-cut evergreen tree in their home for Christmas celebrations. An alternative to using traditional, large, fresh-cut or potted Christmas trees could be forcing these evergreen species in a small (≈1-L) container that could be displayed on a tabletop. We initiated this study to determine consumer preferences and marketability for six evergreen tree species produced for tabletop display and used three decoration themes and three price points. We constructed a web-based survey in which 331 participants were compensated with a $5 e-coupon for viewing 27 photographs of tabletop trees and providing preference and use information. The conjoint model accounted for 91.2% of the variance and showed that consumers valued tree species as the most important attribute (61% of the tree value), with decoration color/theme the second most important feature (27%) and, last, price (12%). Black Hills spruce (Picea glauca var. densata (Moench) Voss) was the most preferred species overall, and red was the most preferred decoration theme. Logically, the lowest price point was the most preferred. However, price was the most important attribute for participants younger than 25 years. The importance of price decreased as participant age increased until age 60, when price became a more important component. With a cost of production of $5.45 and decoration and shipping estimated at an additional $4.00, the product could be a profit generator priced at any of the tested price points ($14.95 and above).