Growers must make irrigation management decisions every day, like when to irrigate, how much water to apply, which plants to irrigate and how to maximize efficiency. There are also many local and state water regulations to which the grower must adhere, and it’s the grower’s responsibility to plan and manage their water supplies to be able to meet those regulations. Increasingly, competition for water resources is affecting how these decisions are made. Luckily, there are resources available to help nursery owners improve their irrigation and water conservation strategies.
Dr. Amy Fulcher, assistant professor at the University of Tennessee’s Department of Plant Sciences and Dr. Tom Fernandez, associate professor of Michigan State University’s Department of Horticulture worked on a series of extension publications examining the impact and social acceptance of sustainable practices in ornamental crop production systems. The work was partially funded by the U.S. Department of Agriculture’s Specialty Crop Research Initiative.
In this work, Fulcher and Fernandez present several strategies to reduce water consumption in nurseries. These include grouping plants by relative water needs and container size and using cyclic irrigation.
Grouping plants by perceived irrigation needs (high, medium, low) into irrigation zones is a common strategy employed by growers. Grouping plants by water needs along with proper spacing can reduce water consumption tremendously.
Another conservative irrigation strategy is cyclic irrigation, in which the total daily volume of irrigation water is applied in multiple irrigation events with a minimum of one hour between irrigation events. Using cyclic irrigation can reduce runoff by 30 percent, compared with conventional continuous irrigation.
Using amendments, such as calcined clay, to increase the substrate water-holding capacity also can reduce water use. Growers have many options for increasing water-use efficiency in the nursery. These include refining irrigation scheduling, irrigation volume and irrigation delivery.
The University of Tennessee Institute of Agriculture also has published a 114-page reference manual entitled "Nursery Irrigation: A Guide for Reducing Risk and Improving Production." This guide was compiled by Fulcher and Whitney Yeary, extension assistant, plant sciences and Brian Lieb, associate professor, Biosystems Engineering and Soil Science. It includes sections on water sources, water testing, water conservation practices, irrigation systems and more. One uniquely valuable feature of the manual is the "success stories" that are used to illustrate the principles of each section. These stories share how a nursery has improved its production process by focusing on an aspect of irrigation.
A study done by the University of Guelph, in collaboration with ICT International Pty. Ltd. (Australia), and Root Rescue Environmental Ltd. assessed conventional irrigation management using automated stem psychrometers. The research was presented at the VII International Symposium on Irrigation of Horticulture Crops.
Along with assessing conventional irrigation strategies, the study’s objectives were to monitor environmental conditions, impose irrigation management strategies based on cumulative water stress integrals, analyze and correlate cumulative water potential and vapor pressure deficit (VPD) integrals. From there, it would derive “VPN coefficients” for each species to predict and manipulate water stress responses. Acer rubrum and Thuja occidentalis were both tested.
The study’s results suggested that conventional nursery irrigation practices significantly over-irrigated. By measuring stomatal function responses and water stress levels, the researchers were able to determine that a system utilizing VPN coefficient had several advantages, including being less wasteful with water than conventional nursery irrigation. Also, the study found conventional methods rarely allowed plants to reach this level of stress.
Top photo: Decker's Nursery, Groveport, Ohio
Bottom photo: The Siebenthaler Company, Dayton, Ohio