Implementation on the Farm
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Q and A: Windbreaks
The following Question and Answer information is intended to help planners communicate with land users and to help develop windbreak designs and estimate costs for the application. Once contracts have been tentatively funded, a site visit to finalize the windbreak design will be needed.
Q. Should the windbreak encircle the entire area?
A. Yes. No. Maybe. The correct answer depends upon what type of windbreak is needed and whether any site limitations are present. If site conditions (buildings, utilities, roads, property lines, etc.) are not limiting, then a 2 sided windbreak for energy or snow protection and a 4 sided windbreak for odor control is best. Vegetative plantings for visual barriers will be needed on any side that needs screening. Site conditions or air circulation issues may necessitate the elimination or reduction of rows on one or more sides.
Q. How many rows are needed for a windbreak?
A. The minimum number of tree rows for addressing odor concerns is three (see table below). One row must be an evergreen and one row must be a shrub. The minimum number of tree rows for a farmstead is also three. Less than 3 rows are only acceptable when physical limitations such as property lines, roads, access limitations, structural barriers, or topographic limitations are present. Increasing the number of rows to five will provide additional benefits for wildlife. Air circulation issues may necessitate fewer rows to increase windbreak porosity.
Q. What spacing is needed between trees and/or shrubs within a windbreak row?
A. Usually the spacing between shrubs in the row will be 5-6' and 10-15' between trees. This close spacing will achieve the needed windbreak density quicker. Thinning may be necessary or desirable as trees approach maturity. Wider spacing, as well as fewer rows, might be needed on the south and/or west sides of naturally ventilated buildings or protection areas where wind flow in the area is a concern.
Q. What spacing is needed between windbreak rows?
A. The spacing between rows should be from 20' to 50'. Wider spacing will allow for more undulation of air currents which helps to dissipate wind velocities and trap volatile organic compounds (VOC - the smelly stuff).
Q. How much land will be needed for a windbreak?
A. Most windbreaks will take up between 0.5 - 1.5 acres. This will depend on the species used, number of rows, between row spacing, and site limitations. To determine the area needed for the windbreak, add the between row spacing together and add 10' of maintenance area on each side, multiply by the total length of the windbreak, and then divide by 43,560 square feet. For example: a 3 row windbreak with 20' spacing between rows and 1000' in length .. [(20+20+10+10) X 1000'] / 43560 = 1.4 acres.
Q. Is supplemental water required for a windbreak planting?
A. No. However, adequate water is critical to the survival of woody plantings. Temporary irrigation or supplemental watering will help ensure the survival of woody plantings. Temporary irrigation systems typically consist of 1" main poly lines with 1/2 - 3/4" laterals down each row with a drip nozzle/emitter for each tree that can provide 1 gal/hour of water. Using lagoon water is not recommended because of possible salt build up and uncertain fertility composition.
Q. What type of site preparation will be needed before trees and shrubs can be planted?
A. Site preparation will be needed in each application. Tillage and/or chemical methods are acceptable. If grass cover is present it should be eliminated within all rows before any planting begins.
Q. What kind of trees should be planted in the windbreak?
A. Selecting the species of trees and shrubs to plant will vary at each facility and farm
site. Species selection should be based on the characteristics of each site, including:
soil type, natural drainage, common wind conditions, annual precipitation, natural range
of each woody species and site needs. In addition, to maximize particulate trapping for
odor windbreaks, select species with high leaf surface roughness (plants with leaf hairs,
leaf veins, small leaf size), complex leaf shapes, large leaf circumference to area ratios
and medium to rapid growth rates.
Q. What is the difference between seedling and container plants?
A. Size, cost, and survival. Seedlings are easier to handle but have fewer existing roots and are generally less than 2 feet tall. Container trees have a denser root system, will get off to a faster start because they have a greater root network for taking up water and nutrients, have much better initial survival, and can be as tall as 5-8 feet. Seedlings are more affordable ($.20 - .90) than container plants ($9 – 25), easier to plant, and cheaper to replace. Seedlings can also be shipped to any address but container trees will likely need to be picked up by the land user at the retail or wholesale outlet. After 10 -15 years, the difference in height growth and maturity, between seedlings and container trees, may be undetectable.
Q. Is weed control required for windbreak plantings?
A. Yes. Control competing vegetation for the life of the planting or until plants close the area and shade out competition. Suitable weed control methods include chemical control, weed mat barriers, mulch, and/or mechanical cultivation.
Q: Why should I use a mycorrhizae root dip when planting seedlings?
A. Mycorrhizae fungi exist in all naturally forested areas and colonize tree roots. It extracts sugars from the roots for its own purposes and acts as a large extension of the root system, adding as much as 700% more absorption network. This mechanism enhances drought survival and improves tree growth. This fungus may not be present (or in low numbers) in pastures or on prairie soils but can easily be added to the site with a root dip procedure. Inoculation cost is approximately a penny per tree. The root dip can be ordered from many landscape/nursery or forestry supply catalogs.
Q. What are the survival needs for windbreak plantings?
A. Inventoried after "leaf out" during the spring or summer of the second year, 90% of all trees and shrubs planted need to be living, with no two adjacent, within row plants missing. Any noted deficiencies will need to be addressed with replanting.
Q. Where can I find additional guidance on windbreaks?
A. Additional technical questions on windbreaks can be directed to personnel from Missouri Department of Conservation, Natural Resources Conservation Service, University of Missouri Extension, and University of Missouri Center for Agroforestry.