Planning Field Shelterbelts

Introduction

Properly planned shelterbelts provide many benefits to farm families. They reduce wind erosion, control blowing snow, protect livestock, trap snow, and increase crop yields. Shelterbelts also provide diversification opportunities, habitat for wildlife, and beautify the farm.

Planning your Shelterbelt

Proper planning of a shelterbelt involves reviewing your present requirements, assessing your future needs, estimating the quality of existing shelterbelts and planning new shelterbelts for unprotected areas of the field.

Begin by mapping out your field using a scale of 2.5 cm = 134 m or 1 in = 440 ft. Mark out locations of existing trees, sloughs, buildings, farm access roads and power lines. Next, draw in the prevailing wind directions and note areas where excessive snow accumulation can cause problems.

To eliminate problems with snow buildup, keep all trees at least 30 m (100 ft) from main buildings and driveways. Mark this distance around the perimeter of the yard to indicate the closest field shelterbelts should be planted to the yard (figure 1). Also check with your R.M. to determine minimum set-back distances from municipal roads. The Department of Highways regulations must also be followed where applicable.

Shelterbelt Design

Decide on the number of shelterbelt rows required to properly protect the field. Up to five rows of trees on a section planted at right angles to the prevailing winds (usually north-south belts) are recommended on highly erodible soils to provide protection from prevailing prairie winds. Rows on the north and south ends of the field, running east-west, can also be planted to maximize protection. Field access roads should be located in the east or south corners as most erosive winds come from the North or Northwest. In some areas of the prairies the problem winds may be from the south. In these areas the main rows should run east-west to be at right angles to prevailing winds.

The field shelterbelt should be tall and long-lived. Since area protected is directly related to the height of the shelterbelt, the planting of tall trees is recommended wherever possible. Species such as green ash and Scots pine are tall and, therefore, can provide a significant area of shelter down wind. The density required will depend on your specific site. The denser the shelterbelt the greater the wind protection and, therefore, areas with erodible soils should consider denser shelterbelts. The size of the snowdrift trapped by the belt is also affected by the density. Denser shelterbelts trap snow in a shorter, deeper drift (figure 2).

Green ash is a less dense species and, therefore, snow distribution behind a green ash shelterbelt will be more evenly spread across the field. Shrubs, such as caragana, chokecherry and Villosa lilac, provide superior snow trapping and wind protection due to their density but are not as tall as the ash or pine. These species can be used in areas where snow is not a concern, or where maximum protection is required.

To get the appropriate density use species possessing the desired characteristics. Many people choose to mix ash into a shrub row to provide extra height. This results in a shelterbelt with the density of a shrub row, but the height of a tree row.

A series of shelterbelts is a more effective shelterbelt system then a single row planted to protect a large area. The first row to meet prevailing winds should be less dense allowing for a more even snow distribution across the field. As this first row may intercept snow blowing from a considerable distance you should be aware of the amount of snow this shelterbelt could potentially trap. The other rows in the shelterbelt system can consist of denser species as there will be significantly less snow for these trees to trap. These denser shelterbelts further into the system can only trap the snow the earlier shelterbelts let through. See figure 3 for an illustration of such a shelterbelt system.

Although several rows per quarter section are recommended, any shelterbelt in the field will be a benefit. Many shelterbelt systems have begun with the planting of a single half-mile field shelterbelt row.

Selection of appropriate tree and shrub species is very important. Each species has its own characteristic height, width, density, longevity, growth rate and resistance to insects and diseases. See Table 1 for further information on species recommended for field shelterbelts.

Multi-Row Multipurpose Belts

Although field shelterbelts in Canada have traditionally consisted of single row, single species shelterbelts, there are several benefits to planting multiple row, multiple species shelterbelts called forest belts. These multiple row belts provide superior wind protection as there are more rows of trees to slow the wind. They also trap more snow but some of this snow is held within the tree rows themselves and, therefore, is not a hindrance to regular field work. By planting multiple species you can reduce the risk of a single disease or insect wiping out your shelterbelt system. Dutch elm disease is a classic example of what can happen when too much dependence is placed on a single variety of tree or shrub. Finally, a world of diversification opportunities reside in these multi-species, multi-row shelterbelts as Manitoba maple an be tapped for syrup, chokecherry and other fruiting varieties can provide a valuable food supply for jam and jelly production, and wood can be gathered for a variety of uses. In addition, these multi-row belts provide prairie wildlife species with better habitat. See figure 4 for an example of a forest belt design.

Shelterbelt Spacing

The spacing recommendations within and between rows is very important (Table 2).

Remember, you are planting seedlings which will eventually develop into mature trees reaching heights up to 15 m (50 ft) and widths up to 10 m (30 ft). In forest belt plantings leave sufficient space between shelterbelt rows to permit the passage of maintenance equipment in the early years. Correct spacing between trees within the row allows adequate light, moisture and nutrients for proper growth.

When you have selected appropriate tree species and determined the number of rows, draw them on your field shelterbelt plan. Attach a copy of your plan with your application for trees. The Shelterbelt Centre accepts applications on a first come first served basis starting June 1 for delivery the following spring.

Weed Control in Shelterbelts

Weed control is necessary to ensure a successful shelterbelt planting. Like our gardens, shelterbelts will suffer when weeds are allowed to grow unchecked. There are a variety of different weed control strategies including herbicides, plastic mulch, flax shive mulch and others.

Shelterbelt Planning Around Dugouts

A shelterbelt can be designed to trap snow to help replenish water supplies and reduce the hot, dry winds that increase evaporation from dugouts. Trees should be planted at least 15 to 30 m (50 to 100 ft) from dugouts depending on drainage. If the land slopes away from the dugout, then plant the shelterbelt closer to allow the trapped, melted snow to drain into the dugout. Do not plant any closer than 15 m (50 ft) to prevent the shelterbelt from using stored water and contaminating the water with foliage.

Multiple rows of shrubs, such as caragana, lilac and chokecherry, provide a dense effective snow trap. Conifers, like Colorado spruce, white spruce and Scots pine, can be used for greater wind protection. Follow shelterbelt spacing recommendations as previously mentioned or see the Shelterbelts for Dugouts.

Points To Consider In Planning

1. Keep all trees at least 100 ft from roads, buildings, etc. Check with your rural municipality regarding tree planting regulations next to road allowances, and with the Department of Highways regarding tree planting regulations next to highways.
2. Plant only as many trees as you can care for. More trees are killed by weeds and grass than by any other cause. Refer to the brochure Weed Control in Shelterbelts.
3. Avoid any access roads or openings in the shelterbelt which will allow the prevailing winds to blow unchecked across the field. Place field access openings where the least amount of wind will pass through.
4. Protect shelterbelts from livestock as they will eat, trample or rub the trees, destroying them. Fence off the planting if necessary.
5. Include fruit-bearing shrubs, such as chokecherry, buffaloberry and sea buckthorn, to benefit wildlife. Consider planting forest belts consisting of multiple species and multiple rows.
6. Ensure dead trees are replaced as soon as possible.