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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

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

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

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

Şemsettin Kulaç, Pascal Nzokou, Deniz Guney, Bert Michael Cregg, and Ibrahim Turna

Four-year-old seedlings of Abies fraseri [(Pursh) Poir] (fraser fir) were grown in semicontrolled conditions in hoop houses with five watering regimes (0.00, 0.62, 1.25, 2.50, and 3.70 cm/week) with the goal of determining the seasonal variation in the physiological response to drought stress. Drought stress was monitored by measuring predawn (Ψpd) and midday (Ψmd) potentials in a subset of plants from each treatment. Physiological variables monitored were chlorophyll fluorescence (F v/F m), Chl a, Chl b, total carotenes, and total carbohydrate concentrations. Morphological characteristics including height growth, root collar diameter, and terminal shoot growth were also measured. Predawn stem water potential values were generally higher (–0.8 to –1.9 Mpa) than midday values (–1.3 to –2.9 Mpa). Irrigation consistently increased Ψpd and Ψmd compared with non-irrigated treatments. Photosynthetic pigments (Chl a, Chl b, and carotenes) decreased midseason (14 July) and increased toward the end of the season (25 Aug.) in predawn and midday measurements. There was a significant effect (P < 0.05) of drought stress on photosynthetic pigment concentrations in predawn and midday samples in the late-season measurements (25 Aug.). These results were accompanied with a similar significant difference in F v/F m between non-irrigated and irrigated trees. We concluded that significant effects observed on photosynthetic pigment concentrations in some of the treatments did not affect carbohydrate concentrations. Exposure of A. fraseri to water stress did not cause a reduction in supply of metabolic carbohydrates; consequently, the decline and mortality in water-stressed plants can only be the result of hydraulic failure caused by xylem cavitation leading to cessation of water flow in tissues, desiccation, and cellular death. Further studies are needed to confirm these preliminary conclusions.

Free access

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

Container-grown woody ornamentals were irrigated according to a percentage of daily water use (DWU) or a traditional irrigation rate to evaluate plant growth, irrigation volume, runoff, and nutrient loss from each irrigation treatment. Deutzia gracilis Sieb. and Zucc. ‘Duncan’, Kerria japonica (L.) DC. ‘Albiflora’, Thuja plicata D. Don. ‘Atrovirens’, and Viburnum dentatum L. ‘Ralph Senior’ were grown in 10.2-L (# 3) containers under four overhead irrigation treatments: 1) a control irrigation rate of 19 mm 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 with one application of 100% DWU followed by two applications replacing 75% DWU (100–75–75). Applications were separated by at least 24 h. Total irrigation applied for the 100DWU, 100–75, and 100–75–75 treatments was 33%, 41%, and 44% less, respectively, than the total water applied by the control treatment of 123 L per container. Plants grown under the three DWU treatments had a final growth index greater than or equal to plants irrigated by the control treatment depending on species. Daily average runoff volumes from production areas irrigated with 100% and 75% DWU were 66% and 79% lower than average control runoff of 11.4 L·m−2·d−1 across all collection days. Quantity of NO3 -N lost daily across all collection days for the 100% DWU and 75% DWU irrigation volumes averaged 38% and 59% less, respectively, than the control. Daily losses of PO4 3–- P quantities across all collection days under the 100% and 75% DWU volumes were 46% and 74% lower, respectively, compared with the control. Irrigating according to the DWU treatments used in this study reduced irrigation and runoff volumes and NO3 -N and PO4 3–-P losses compared with a control of 19 mm per application while producing the same size or larger plants.

Open access

Myounghai Kwak, Jeong-Ki Hong, Eun Sil Lee, Byoung Yoon Lee, Min Hwan Suh, and Bert Cregg

Korean fir (Abies koreana) has been cultivated for less than 100 years, mainly in the United States and Europe. Using nuclear microsatellite, mitochondrial, and chloroplast markers, we investigated the origin of cultivated korean fir from South Korea (KC group) as well as the United States and United Kingdom (EU group), and compared these samples to published data from wild populations. All genotypes in the EU and KC groups were most closely related to the wild individuals from Mt. Hallasan, the southernmost A. koreana population on Jejudo Island (South Korea). However, the presence of the chloroplast haplotypes clustered with Abies balsamea in two EU cultivars and the higher diversity values of the EU group compared with the wild individuals from Mt. Hallasan infer a certain level of introgression from different species during cultivation. The EU group had a higher inbreeding coefficient and linkage disequilibrium, and a smaller proportion of rare alleles, than the wild populations. This suggests that the genetic characteristics of korean fir cultivars reflect strong artificial selection pressure for desirable horticultural traits and asexual reproduction. Last, this genetic background study suggests that the other wild populations in the Korean peninsula can serve as valuable genetic resources for future breeding.

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).

Full access

Xueni Wang, R. Thomas Fernandez, Bert M. Cregg, Rafael Auras, Amy Fulcher, Diana R. Cochran, Genhua Niu, Youping Sun, Guihong Bi, Susmitha Nambuthiri, and Robert L. Geneve

Containers made from natural fiber and recycled plastic are marketed as sustainable substitutes for traditional plastic containers in the nursery industry. However, growers’ acceptance of alternative containers is limited by the lack of information on how alternative containers impact plant growth and water use (WU). We conducted experiments in Michigan, Kentucky, Tennessee, Mississippi, and Texas to test plant growth and WU in five different alternative containers under nursery condition. In 2011, ‘Roemertwo’ wintercreeper (Euonymus fortunei) were planted in three types of #1 (≈1 gal) containers 1) black plastic (plastic), 2) wood pulp (WP), and 3) recycled paper (KF). In 2012, ‘Green Velvet’ boxwood (Buxus sempervirens × B. microphylla siebold var. koreana) was evaluated in 1) plastic, 2) WP, 3) fabric (FB), and 4) keratin (KT). In 2013, ‘Dark Knight’ bluebeard (Caryopteris ×clandonensis) was evaluated in 1) plastic, 2) WP, and 3) coir fiber (Coir). Plants grown in alternative containers generally had similar plant growth as plastic containers. ‘Roemertwo’ wintercreeper had high mortality while overwintering in alternative containers with no irrigation. Results from different states generally show plants grown in fiber containers such as WP, FB, and Coir used more water than those in plastic containers. Water use efficiency of plants grown in alternative containers vs. plastic containers depended on plant variety, container type, and climate.