ATTRA - National Sustainable Agriculture Information Service
PO Box 3657
Fayetteville, AR  72702
Phone: 1-800-346-9140 --- FAX: (479) 442-9842

By Steve Diver and Lane Greer NCAT Agriculture Specialists May 2000 (Revised Nov. 2001)

The PDF version of this document is available at {pdf lcoation} 9 pages — 287 kb

---

Field Production

Until the 1950s, virtually all nursery production was done in the field. Field production is still widely used to produce bare-root seedlings for conservation plantings, fruit trees, and nursery liners. The most profitable product of field nurseries is B&B shade trees for the landscape industry. In-ground production is well adapted to tap-rooted tree species, mass plantings, inexpensive establishment, and large caliper (trunk diameter) size. Disadvantages include a higher percentage of plant loss and longer establishment periods after transplanting.

Field nursery production involves the use of unique soil management practices. Soil-building cover crops and crop rotations are important to maintain good soil structure, fertility, and organic matter. Living mulches are cover crops planted in the aisles to hold the soil, provide traction, increase water infiltration, and suppress weeds. Legume cover crops fix nitrogen and may be used to reduce the amount of nitrogen fertilizer applied each year. See ATTRA's Overview of Cover Crops and Green Manures for further information and resources.

Integrating living mulches, cover crops, and the application of high-quality composts into field nursery operations are the quickest ways to improve a nursery soil. For fewer pest problems, a diversity of species should be planted, rather than a large block of a single species followed by a large block of another. Habitat management for beneficial insects can also be practiced in a field situation. For more information on this, see ATTRA's Farmscaping to Enhance Biological Control.

Nursery equipment and irrigation systems for field nursery production are unique. Suppliers are listed in the Nursery Management and Production Buyer's Guide and in the magazine American Nurseryman. See the Resources section for contact information.

A recent innovation in field nursery production is the use of in-ground fabric containers, sometimes called root control bags or field grow bags. These containers were developed in the early 1980s by Dr. Carl Whitcomb at Oklahoma State University. The bags have a fabric or clear polyethylene bottom stitched or glued to walls made of nonwoven fabric, and they come in several sizes (31). In theory, they combine the best qualities of container and field production. The advantages of field grow bags are numerous: they enhance rooting; fewer roots are lost at transplanting (80% of the roots are left intact); harvesting is easier; they save labor and time; no special machinery is needed at harvest; and they can be harvested year-round (B&B are normally harvested only during dormancy) (31). There are also disadvantages: the initial investment in grow bags; more need for staking and water after transplanting; damaged bags cannot be used; mechanical cultivation and precise fertilizer application are difficult; and bag removal can be difficult and time-consuming (31).

At this time, however, perhaps the greatest disadvantage of growing in bags is marketing the plants. Few people know of the advantages of growing in bags and find bagged trees less convenient to handle than containerized trees. One way around this is to grow the plant in a pot for the last year of production.

An important consideration in B&B production is the loss of 200-250 tons of topsoil per acre at each harvest. The digging and removal of topsoil from B&B nursery operations is a practice that can, over the long term, seriously deplete the farm's most important resource. There are two options to fight topsoil depletion: replace it with something else, or have a bare-root operation that does not require topsoil to leave the farm. Many growers have begun using compost to replace some of the topsoil that is lost, but applying more than 40 tons of compost per acre is not recommended.

Back to Table of Contents

Weed Control

Weed control in modern field nursery production is based on the use of herbicides. There are many excellent non-chemical alternatives, however. These include mechanical cultivation, cover crops, living mulches, weeder geese, flame weeding, plastic mulching, fabric weed barriers, and organic mulching.

Back to Table of Contents

 

Cultivation

Bärtschi-Fobro (32) carries Swiss-made nursery equipment, including a brush hoe for mechanical weed control. The brush hoe, geared to precision weeding in multiple-row seedling nursery beds, features stiff brushes attached to multiple heads on a rotating drum. The brush heads—which disturb the soil surface and dislodge weed seedlings as the drum turns—come in a wide range of widths and can be set to varying distances to allow for interrow cultivation.

 

Flaming

Flame torches, or flamers, may be an option in some nursery situations. Flaming works by searing and disruption of plant cells, not burning of plant tissue. Passing a flamer quickly over a weed is enough to kill the tops of the weeds, but roots can re-sprout new growth. Broadleaf weeds are more susceptible to flaming than grassy weeds. Flaming will need to be repeated every 2-3 weeks to control grasses.

Flame weeders can be used to prepare a stale seedbed (by flaming off the first one or two flushes of weeds to emerge after seedbed preparation) and they can be used for post-emergent weed control. To protect young seedlings from injury, flaming shields should be used. However, taller seedlings, and
certainly trees with well-developed bark, can withstand directed flaming aimed at weeds growing within and between the rows.

Although there is some criticism that flaming is not a sustainable practice because it uses fossil fuels, much less fossil fuel is needed to flame-kill a nursery bed or field of seedlings than would be used to manufacture, transport, and spray an herbicide for the same job (33). For more information on flaming, contact ATTRA.

  Back to Table of Contents

Mulches

Mulches are another way to exclude weeds. They keep out weeds by limiting light, and retain moisture in the soil. Organic mulches should be three to four inches thick and will have to be replenished once or twice a year. Millcreek Manufacturing offers a row mulching machine that can apply mulch and compost to field-grown stock (34). The machine costs around $5,000 and can mulch beds from 18" to 48" wide, from ½" to 10" deep.

Landscape fabric can also be used in field production. A fast way for growers to get into production is to lay cloth in the field, cut or burn holes into it, and then plant the liners or seedlings.

Researchers at Oregon State University found that mulches made of oyster shell, hazelnut shell, and copper-treated geotextile mulches provided good suppression of liverwort, a prevalent weed in many nurseries. These three outperformed mulches of rockwool, peat moss, coarse sand, perlite, and pumice, two herbicides (Ronstar™ and Surflan™), and the fertilizers iron oxide, copper sulfate, and manganese sulfate (35).

  Back to Table of Contents

Living Mulches

In a study conducted in Minnesota in the early 1990s, researchers compared soil cultivation, herbicides, and three living mulches for weed suppression in a field with six species of ornamental trees (36). The three living before planting into it. One sustainable system that yields the same results uses steam to disinfest beds and greenhouses prior to planting. In a field planting, this system could be used to treat planting beds. Steam is "nontoxic, relatively easy to apply, controls the same spectrum of soil pests as methyl bromide, and can be used in a wide variety of climates and conditions" (37).

 

 

For a greenhouse, a small portable boiler is probably the best unit to have. The Sioux Steam Flo, available from Sioux Steam Cleaner Corporation (see Suppliers for contact information) will work for greenhouse operations. The Sioux Steam Flo costs about $5,700. For small beds in the field, larger units are available from Saskatoon Boiler Manufacturing in Canada (see Suppliers).

The important differences in steam machines include how much heat they are putting out, how portable they are, and how far into the mulches they used were `Norcen' bird's-foot trefoil, `Wheeler' winter rye, and a grass sod consisting of 80% `Eton' perennial ryegrass and 20% `Ruby' red fescue. The grass sod provided excellent weed control, but it was overly competitive with the trees. The trefoil became infested with weeds. The winter rye, which was killed with herbicides and then acted as a mulch, not only provided good weed control, but also increased water infiltration and soil moisture, evened out soil temperature fluctuations, reduced soil bulk density, improved nutrient cycling, and reduced field maintenance costs. In general, the cover crops tended to reduce annual weeds and favor perennial species. For more information on living mulches, contact ATTRA.

  Back to Table of Contents

Steam

For years, conventional production systems have used methyl bromide to sterilize the soil soil the steam penetrates. Although most machines heat only the top 3-6 inches of soil, temperatures are high enough to kill most weed seeds. Machines that heat the soil to 140°F for at least 30 minutes will kill pest fungi, bacteria, nematodes, and weed seeds.

  Back to Table of Contents

Solarization

Soil solarization is another option for killing pests and can be done before beds are planted to trees, shrubs, or perennials. Again, only the beds where plants are to be placed would be treated. The basic principle of solarization involves stretching sheets of clear plastic across moist ground. Solar radiation heats the soil and kills pests there, including weed seeds and harmful insects. Solarization can kill both annual and perennial weeds, if summer temperatures climb high enough.

Solarization can also be used to disinfest potting media (old media that is to be re-used, or soil-based media). To do this, one must enclose the media in plastic bags and leave them in the sun for two to three weeks. Two layers of plastic kill more pests and work about four times faster than one layer (38). For more information on soil solarization, contact ATTRA.

  Back to Table of Contents

Harvest and Storage

At some point, field-grown trees and plants must be dug. (See the Resources section for manufacturers of tree diggers.) Often, these plants are stored after digging. In conventional production systems, trees are dug in late fall or early winter and stored in warehouses until early spring. During this time, bare-root trees are sprayed with fungicides and bacteristats to keep problems from arising.

Researchers in Rhode Island experimented with Taxus B&B stock to see if they could prevent the plants from "rooting out," a condition where the roots grow into the burlap bags. They used Spin Out™ in several different ways (39). Treatments included painting the bottom of the root ball with copper paint, setting the root ball on copper-treated burlap, and rewrapping the root ball with copper-treated burlap before mulching. Although all these treatments provided good control of rooting out after 12 to 16 weeks, the most effective treatments were setting the root ball on copper-treated burlap and leaving it unmulched. The researchers also found that placing the root balls on TexR® Agroliner (a Spin Out™-treated nonwoven fabric) stopped rooting-out completely.

Back to Table of Contents

Costs

The costs of nursery production include overhead, direct, and marketing costs. Overhead costs include all the general costs of operating the nursery—such as taxes, depreciation, interest, rent, utilities, insurance, maintenance and repair, new construction, new equipment, supplies, managerial and administrative salaries, and labor wages that cannot be assigned to a particular crop. Direct costs are those that are tied directly to a crop, such as seed, potting media, and fertilizers. Keeping excellent records is the best way to accurately determine true costs.

Prices should reflect the following: 1) exact production costs, including a reasonable profit, for each crop; 2) prices and quantities offered by competitors; 3) supply and demand for the crop, except for very high-quality products and very loyal customers (1).

The British Columbia Ministry of Agriculture, Fisheries and Food has compiled a Planning for Profit series that details costs involved in establishing and growing several nursery species. These enterprise budgets provide information on expenses and income for perennial and tree crops, grown in containers and in the field. They should provide a rough idea of how much it costs to get into production and how long it takes to make a profit. See their website at <http://fbminet.ca /bc/pfp/ornament.htm> for more information.

For costs associated with establishing a small perennial nursery, see the handbook Requirements and Costs of Establishing and Operating a Three-Acre Herbaceous Perennial Container Nursery (listed in the Resources: Perennials section). See Betrock's hortworld.com http://www.hortworld.com> for a list of horticultural software that focuses on plant selection and nursery management.

At times, it is possible that the competitive price may fall below the cost of production. In this circumstance, a nursery with a unique advantage, such as closeness to market or a superior product, may be able to maintain a higher price that covers costs, without experiencing a serious drop in the number of plants sold.

Although it is desirable to make a profit on each kind of plant, sometimes it is good marketing strategy to grow some plants that may not be very profitable in order to offer a well-rounded inventory. A small nursery might specialize in a few high-quality plants, or produce some plants not carried by larger nurseries (which probably produce only plants that have high sales volumes).

One way to cut production costs is to grow plants in smaller containers. Although the crop sells for less, the cost of media and containers is reduced, as well as the time needed to produce the crop. Similarly, selling plants at wholesale prices means less money received for each plant, but less money (and time) spent on marketing and advertising.

  Back to Table of Contents

Summary

Nursery managers can alter their production systems to incorporate products and techniques that will help the nursery meet some attributtes of sustainable agriculture: reduced fertilizer and pesticide runnoff, attention to soil conservation, recycling of plastics, use of organic waste stream products like compost, and so on. Some nursery growers may find certified organic nursery stock or specialty nursery stock to be an economically profitable option. Promotion of healthy plants as a first line of defense against insects and diseases through soil building practices and nursery media modifications plays a central role in sustainable nursery management. The end result—a greener nursery—can be used to build good relations with neighbors and in marketing your nursery plants to the green industry.

Back to Table of Contents

---

ATTRA is the national sustainable agriculture information service operated by the National Center for Appropriate Technology under a grant from the Rural Business-Cooperative Service, U.S. Department of Agriculture. These organizations do not recommend or endorse products, companies, or individuals. NCAT has offices in Fayetteville, Arkansas (P.O. Box 3657, Fayetteville, AR 72702), Butte, Montana, and Davis, California.