Water Use For Georgia's Nurseries and Greenhouses*

Mark Masters, Flint River Water Planning and Policy Center, Albany State Univ., Albany, GA
Mark Risse and Sheryl Wells Biological and Agricultural Engineering, Univ. of Ga.
Athens, GA

Trees and slower-growing shrubs are often established in in-ground nurseries. Frequently these are large fields.(NAIP Imagery)

Container nurseries use various sized pots to expand growth of cuttings and transplants to marketable sizes. Mulch is often used under pots, and alleys between container beds allows easy access for plant management, irrigation and loading.(NAIP Imagery)

The Green Industry in Georgia is an important agricultural and commercial sector with a great diversity of commodities and production practices. In includes producers of turfgrass sod. That sod may be harvested several times per year and transplanted for rapid sod establishment at new commercial and home construction sites, as well as new and replacement turfgrasses at golf courses and athletic fields. Often sod producers use center pivots or large guns to irrigate their production fields.

Shrubbery and trees are planted as new or replacement landscapes at private and public sites, including homes, businesses, parks, and even highways. Many are initially grown to a suitable size in one of Georgia's many container and in-ground nurseries. Typically these nurseries use a variety of portable or permanent solid set sprinklers, mircro sprinklers, and drip or trickle irrigation sytems to provide water in these frequently changing plantings.

Annual plants, particularly flowers and vegetables, are established in greenhouses or under shade cloth. Many of these structures have seasonal cover for cold weather and storm protection and later shade materials to protect plants from summer heat. Irrigation in greenhouses includes anything from table or ground flood systems to overhead mister and sprinklers. Seedling plants have very small root systems and cannot tolerate drying even for a few hours. The green industry also supplies the commercial vegetable industry in Georgia and elsewhere, establishing the plants that will be transplanted to, typically, drip irrigated fields. These include cabbage and other cole plants, tomatoes, peppers, eggplants and other important vegetable commodities.

The crop with the largest acreage in Georgia is actually pine trees. Harvested pine trees are replanted using trees established in field nurseries scattered throughout the state. Similarly peaches, Asian pear, pecans, blueberry, and other trees and shrubs found in Georgia orchards get their start in greenhouses and nurseries. Even the Christmas trees that find their way into homes and businesses in the Southeast begin in tree farms that are closely managed and usually irrigated to some extent. Water needs of the production sector of the green industry are somewhat unique. They are certainly difficult to characterize.

Generally speaking, the Georgia's Green Industry also involves landscape, lawn, and golf course maintenance. Irrigation, whether accomplished on a small scale by homeowners, or installed and managed by professional irrigation suppliers, accounts for a significant portion of the State's water use and much of its consumption. However, water used in the lawn and landscape sectors of the industry are NOT considered part of the Agricultural Water Demand of the Georgia. The lawn and landscape water use have been accounted for within other sections of he state water demand analyses. Lawn and landscape systems are NOT INCLUDED in the water use numbers discussed on these pages.

Greenhouse and Nursery Water Use: While the industry is diverse the sector that will be included in the computations below is the nursery sector that grows annuals, perennials, and trees for sale. Some are large commercial operations that include several hundred acres of container or in-ground production. Most of these also have greenhouses to germinate seeds or start cuttings in closely controlled environments. Some producers specialize in just a few species; others grow many types of plants. Some of the smaller primary producers began as "mom and pop" nurseries that grew out of avid gardening or small-scale orchards or gardens. Many greenhouses and plant nurseries are retail operations that primarily target the public. They tend to have a seasonal inventory that is purchased from wholesalers in Georgia and elsewhere. Nonetheless, these retailers must use multiple daily irrigations to maintain the value and marketability of their inventory. Some are associated with large chain stores; others are small independent businesses located in urban as well as suburban settings.

State regulations require that farmers and commercial operators who withdraw more than 100,000 gpd from streams and aquifers obtain a permit from the Environmental Protection Division. With that limit, greenhouse and nursery operations that apply water to more than about 15 acres will need permits. However, smaller operations, including most retail outlets will not require a withdrawal permit. This makes their locations difficult to track, and their annual water use volumes, now metered on most farms, unrecorded.

Water use in nurseries is difficult to quantitize under the best of circumstances. Area of container or in-ground plants receiving water changes on an almost daily basis. Even the water needs in greenhouses will vary day to day as inventory changes and plant size increases. To add to the complexity, many container nurseries capture part of the water that necessarily misses the small pots or that drains through them. That water may be captured in ponds or tanks and applied to parts of the nursery where there are plants that are less sensitive to plant diseases or nutrients that may be in that runoff. A few studies, including comercially measured pump volumes at certain production nurseries and publically conducted studies like the Ag Water Pumping and plant research plots, provide some insight to plant water needs. Surveys, like the Cooperative Extension Service Irrigation Surveys and the Green Industry surveys of members, provide additional insight. As a result of these studies and surveys, the state and industry came to consensus in setting some broad categories of water use. For in-ground nurseries average annual use is estimated at 31 in; for container nurseries, 87 in.; and for greenhouses, 121 inches. Greenhouse use numbers recognize that the elevated temperatures can increase consumption to 1/3 in. per day. Since they are under cover greenhouse water use is expected to vary little from year to year of from dry to wet seasons. Plants grown in containers likewise use larger amounts of water than field raised plants or crops. Untargeted, rainfall does little to refill pots that are often smaller than the canopy of the plant growing in them. Transpiration occurs, but the supply to sustain it is that small soil- and root-filled pot. In-ground nurseries are more subject to irrigation variation from year to year. Rainfall can allay part of the annual withdrawal. Although not included in the industry survey, lower management nurseries, like Christmas tree farms, will use less water than higher production, in-ground nurseries.

Greenhouse and Nursery Acreage: Computation of irrigation withdrawals requires some estimate of area of nurseries and greenhouses. Three public surveys exist: the USDA NASS Survey of Nursery Crops; the Georgia Cooperative Extension Service Irrigation Survey; and the UGA Center for Agribusiness and Economic Development's Farm Gate Reports. The NASS survey has been a survey of Georgia's larger producers of ornamental crops -- those who gross more than $100,000 per year from sales of ornamentals. Their last 2006 Summary showed 8,019 acres in these producers' farms.

The two UGA surveys obtained their information from the county agricultural agents, but the aceage reported typically differs between the surveys. For the state as a whole, The 2008 Farm Gate Survey reported a total of 436 acres in greenhouses, while the 2008 Irrigation Survey reported 241 acres. The 2008 Farm Gate Report showed a total of 12,703 acres in container and in-ground nurseries, while the 2008 Irrigation Survey reported 7374 acres and did not differentiate between them.

In container nurseries, limited rooting systems and small pot openings require irrigation several times per day. Plastic mulch used under plots not only facilitates handling of containers, prevents roots from growing into underlying soil, and keeps weeds out of these areas, but also, permits collection and reuse of irrigation runoff.

Greenhouses and nurseries were the target of advanced GIS mapping in the Ag Water Demand Study between February and April, 2010 This included examination and reclassification of nurseries and greenhouses originally mapped by EPD and SWCC. The final map identified 177 locations with one or more greenhouses with 249 acres in those. The mapping found 8345 acres in nurseries that ranged in size from 0.25 acres to more than 500 acres. These nurseries were labelled as in-ground, container, or low-input as evidenced by visible irrigation, mulch, covers and plant arangement seen in NIAP imagery.

At recommendation from the Green Industry and in concurrence with EPD officials, the Farm Gate Survey values for acreage of greenhouse and nurseries were adopted for computation of withdrawals for the industry. Values of irrigation amounts explained earlier were used to calculate those annual withdrawals. On a statewide basis, annual withdrawals are approximately 20,000 million gallons or about 54 MGD. No estimate was made by the industry on projected growth in acreage or water use. County by county details are given in the table below.

Data Sets: Nurseries and greenhouses

Countywide Water Use in Greenhouses and Nurseries.
County by County record of total annual water use by this sector of the green industry.
(Excel file - last update 4/20/2010)

Last updated 04/26/2010 James E. Hook
Links reconfirmed 11/7/2012 JEH