Performing Department
Valley Laboratory
Non Technical Summary
Christmas trees are an important specialty crop grown approximately on 4,830 acres in Connecticut with annual sales of approximately $18,000,000. True firs (Abies spp.) are highly valued by customers because of their exceptional needle retention, soft needles, and pleasant aroma. However, the ability to produce most species of conifers grown as Christmas trees in CT, and especially fir trees, is threatened over the long-term by changes in our climate, in part revealed as more frequent weather extremes. Each year, growers experience an average loss of 5 to 30% of seedling trees --likely due to the combined adverse stressful effects of deprived access to water and minerals, heat stress, weed interference, and herbicide injury (unpublished data, Cowles and Aulakh). The initial field establishment of Christmas trees is critically important: poor initial growth is likely to translate into slower growth in succeeding years and thus a longer crop production cycle with higher variation in tree sizes within the age group. Trees that are small or grow slowly are more sensitive to the biotic and abiotic stressors mentioned above. Christmas trees are typically planted bare-rooted with few fine roots and are thus relatively less capable of absorbing water and minerals. Most of the fine roots are destroyed during lifting from transplant beds and those that survive may be injured further or desiccate later during shipping and handling. In addition, the long summer dry spells, higher temperatures and subsequent evapo-transpirational demand (which Connecticut has experienced in three successive years), create non ideal conditions for transplant survival.Kaolin, an aluminum phyllosilicate clay (Al2Si2O5OH4), is a reflective type anti-transpirant that reduces the absorption of radiant energy and thereby reduces leaf temperatures and thustranspirationrate. In fruit orchards, foliar application of kaolin is used to cover leaves and fruit with thin films ofnanoparticles(Boari et al., 2015; Glenn and Puterka, 2005). Published research in various crops have shown beneficial effects of reflective materials such as kaolin clay on transplant survival and growth by reducing heat stress and water loss via transpiration. These benefits are due to kaolin particle films (KPF) reflecting photosynthetically active, ultraviolet and infrared radiations, thus reducing temperatures of treated leaves and fruits and thereby protecting plants against drought stress (Cantore et al., 2009; Glenn, 2012).Antonie et al (1970) reported that kaolin application on orange (Citrus x sinensis), lemon (Citrus x limon), and bean (Phaseolus spp) plants cooled the leaves 3-4°C and reduced transpiration 22-28% under conditions of high light intensity, warm air, low relative humidity, and low wind velocity. Moftah and Al-Humaid (2005) observed enhanced water status, water use efficiency and the photosynthetic activity with the kaolin sprays in water stressed tuberose (Polianthes tuberosa L.) plant.Sulfur is one of the six most essential nutrients needed for healthy growth of Christmas trees. Typically, Christmas trees require 638 kg of nitrogen, 72 kg of phosphorus, 325 kg of potassium, 471 kg of calcium, 62 kg of magnesium, and 41 kg of sulfur per hectare (OSU, 2009). Recently, researchers at the Connecticut Agricultural Experiment Station have noticed reduced incidence of root rots caused by Phytophthora spp., increased tree growth and vigor, and improved weed control with sulfur application (unpublished data, Cowles and Aulakh). It is very likely that the reduced soil pH, as a result of sulfur application, created unfavorable conditions for Phytophthora root rot disease development and weed growth. In addition, changes in soil pH also affect the availability of soil nutrients which in turn affect plant growth and vigor (Chien et al., 2011; Shenker and Chen 2005; Wang et al., 2006). Availability of calcium, magnesium, phosphorus, potassium, and sulfur is higher in the neutral to alkaline pH range whereas boron, copper, iron, manganese, and zinc are more readily available in the acidic to neutral pH range (Brady and Weil, 2007). Low soil pH can also induce deficiencies of macronutrients such as calcium, magnesium, and potassium, and micronutrients such as molybdenum (Miller, 2016). In contrast, boron, copper, iron, manganese, and zinc become deficient at high pH due to their reduced solubility (McKenzie, 2003). Activity of several soil microbes including fungi and bacteria is also affected by changes in soil pH. Incidence of many plant diseases such as damping off and root rots is decreased at pH levels of 5.5 or less (Schmitthenner and Canaday, 1983, Tint 1945, Vaartaja, 1967). Similarly, weed species population ecology also varies with soil pH. Weeds such as velvetleaf (Abutilon theophrasti) and Powell amaranth (Amaranthus powellii) did not perform well and produced low biomass at pH of 4.8 than at pH of 6.0. However, green foxtail grew better at pH 4.8 than at pH 6.0 (Decker et al., 2006; Weaver and Hamill, 1985). Similarly, broomsedge (Andropogon virginicus), red sorrel (Rumex acetosella), and mosses grow well under low soil pH (Derr 2000).Christmas tree's tolerance to soil pH varies with the tree species. For example, Douglas fir (Pseudotsuga menziesii), Colorado blue spruce (Picea pungens), and white spruce (Picea glauca) prefer a soil pH in the range of 6 to 7 whereas Balsam fir (Abies balsamea), Concolor (Abies concolor), and Fraser fir (Abies fraseri) will not perform well on sites with pH above 6.2 owing to their extreme sensitivity to high soil pH (Crozier and Hardy, 2015, MSU extension, 2019). Our data from preliminary research on Phytophthora root rot and weed management in Christmas trees revealed that nearly all trees display some sulfur deficiency during the year of transplant (unpublished data, Cowles and Aulakh). Although the improvement observed in plant color and health during the transplant year following soil acidification with elemental sulfur (2500 kg ha-1) was less than optimal, a doubling of the terminal growth was observed the next year, compared to trees not treated with sulfur (unpublished data, Cowles and Aulakh). Wiedenfeld (2011) observed that the effect of sulfur application (1120 kg ha-1) on soil pH was gradual, causing only a slight reduction in the application zone after one year; but the effect was long lasting, resulting in continuing substantial declines in soil pH through four years after the first sulfur application.In addition, weeds if left uncontrolled, will use up the stored soil moisture and nutrients which may cause as high as 80% mortality of the new transplants (Kuhns and Harpster, 2003). Weeds routinely outcompete newly transplanted trees and impair their photosynthetic efficiency by depriving exposure to sunlight. Christmas tree growers often use preemergence herbicides for weed control to prevent competition during the post-transplanting phase (Ahrens and Newton, 2008; Brown et al., 1989; Peachy and Miller, 2017). Christmas tree tolerance to herbicides varies with tree species and age of the transplant (Ahrens and Mervosh, 2000; Ahrens and Newton, 2008; Kuhns and Harpster, 2005; Weston et al., 2005). Hexazinone plus sulfometuron- methyl provided higher and longer duration control of several annual broadleaf and grassy weeds in plots treated with elemental sulfur (personal observation, Aulakh). There is no published research on effect of elemental sulfur on weed control efficacy of preemergence herbicides.
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Goals / Objectives
The objectives of this research project are to evaluate:Role of a kaolin clay and elemental sulfur in survival, establishment, and growth of newly transplanted Christmas trees.Effect of elemental sulfur on weed diversity and efficacy of preemergence herbicides.
Project Methods
Experiments will be established in a split-split plot design with three replications at the Valley Laboratory Research Farm of the Connecticut Agricultural Experiment Station in Windsor and a commercial Christmas tree grower's farm in Somers, CT. The main plot (18 m x 6 m) will consist of two rates of elemental sulfur: 0 and amount needed to bring the soil pH to 4.5, and the subplot (6 m x 6 m) will consist of three rates of Surround WP (kaolin clay) at 0, 30, and 60 kg ha-1, and the sub-subplot (2 m x 6 m) will consist of three preemergence herbicide treatments; none, flumioxazin, and simazine plus oryzalin at standard application rates. Each sub-subplot will have two rows, four (plug + 2) Fraser trees (Abies fraseri) each, with rows spaced at 1.8 m and trees within a row spaced at 1.5 m. Elemental sulfur will be surface applied in the late fall or early winter (October/November) of 2020 before planting trees in the following the spring of 2021. Surround WP (kaolin) will be applied as a foliar spray in July-August during high stress period. A total of 2 or 3 Surround WP applications will be made at 2 to 3 week intervals from July through August. Herbicide treatments will be applied in the spring of 2021 to the newly transplanted trees with a CO2-pressurized backpack sprayer calibrated to deliver 280 L ha-1 at 276 kPa equipped with a single AIXR 11003 flat-fan nozzle spray wand (TeeJet, Spraying Systems Co., P. O. Box 7900, Wheaton, IL 60189).Soil samples will be collected in fall 2020 from multiple locations up to 10 cm depth in each main plot to determine the amount of elemental sulfur required to bring the soil pH to 4.5. Soil samples will be collected again at 12, 24, and 36 months following sulfur application from multiple locations within the main plots to determine changes in soil pH. Baseline data will be collected on initial Christmas tree transplant height and stem diameter at the time of transplanting. Observations will be recorded on Christmas tree stand, height, leader length, and in each sub-subplot at 18 weeks after transplanting. Data will also be collected inside a 50 x 50 cm quadrat on weed species diversity and density in each sub-subplot at 6, 12, and 24 weeks after herbicide application. Visual percent weed control will be assessed at 6, 12, and 24 weeks after herbicide application in each sub-subplot on a 0 to 100% scale where 0 equals no control and 100 equals complete kill of aboveground growth. Surround WP and preemergence herbicide treatments will be continued for three consecutive years and data on various response variables will be recorded each year.Data on response variables will be subjected to ANOVA using the PROC Glimmix procedure in SAS version 9.3 (SAS Institute Inc, Cary, NC). Elemental sulfur, kaolin clay, and herbicide treatments will be considered as fixed effects; while experimental site, year, replication, and their interactions with fixed effects will be considered as random effects in the model.