Field shelterbelts

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Description - Field shelterbelts

Prairie landscape with narrow fields protected from wind erosion by field edge shelterbelts

Field shelterbelts are rows of trees and shrubs planted on agricultural lands. The primary objectives of field shelterbelts are protecting crops and soil from wind erosion, catching and distributing snow and improving the micro-climate for crop production. Long-term benefits to you and the environment include wildlife habitat enhancements and visually appealing landscapes.

Design your field shelterbelt to accommodate the size of your agricultural equipment. Consider field access, shelterbelt location and equipment manoeuvrability in your plan.

Main objectives include reducing wind erosion, providing crop protection, increasing irrigation efficiency and improving wildlife habitat. To control soil erosion, shelterbelts should be planted to block the prevailing winds during the times of greatest soil exposure - winter and early spring. Shelterbelts protect fall-seeded small grains like winter wheat from summer and winter winds.

To recharge soil moisture with drifting snow, shelterbelts should be placed perpendicular to the prevailing winter winds.

Planning

Using the recommended species and spacing is an important component of planning. Good planning can reduce tree competition with adjacent crops and prevent excess snow entrapment. Increased crop yield and moisture accumulation in the sheltered zone more than compensates for the moisture used and land occupied by field shelterbelts. The protection zone provided by a single shelterbelt is limited. Therefore multiple shelterbelts may be required to protect the entire field.

The area protected will increase as the shelterbelt matures. On most soils, shelterbelt rows can be spaced 200-250 metres (m) apart. Up to four shelterbelt rows can be planted in a square 64 hectare field. Plant your rows at right angles to the prevailing winds. In most areas on the Prairies, prevailing winds come from the northwest and west directions, so the recommended shelterbelt planting is north to south.

The first shelterbelt should be on the extreme west side of the field, with the remaining shelterbelts dividing up the area.

Leave adequate room at the ends of each shelterbelt row to allow equipment access to the field rather than inserting an opening within the shelterbelt. Wind, when funnelled through a gap, increases in speed. If you need field access within the shelterbelt rows, stagger the access points (i.e. not in a straight line) to limit wind funnelling.

Snow drifts accumulate mostly on the leeward or protected side of a shelterbelt. In high snowfall areas, a single, low density row distributes snow evenly across the field. This reduces deep snow drift formation. A gap between the ground and the shelterbelt's lowest branches increases this effect.

A multiple-row shelterbelt will trap snow between its rows. Additional benefits include other wood and fruit products as well as enhanced wildlife habitat.

Areas with low to moderate snowfall may require a denser shelterbelt to capture as much snow as possible. Additional field management practices can aid in improving in-season soil moisture conditions: tall stubble to enhance snow trapping in-field, and crop residue to reduce soil moisture evaporation.

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Description - Protection provided by a single shelterbelt is limited and multiple shelterbelts may be required to protect a large field.

The figure shows a sketch of a farm field. Adjacent to the field are a highway running east-west and a municipal road running north-south. Prevailing winds are indicated from the northwest and winter storms from the southeast. Features on the sketch include an overhead powerline, a low area in the field and a bluff of trees. Proposed field shelterbelts are drawn onto the sketch running north-south starting 45 m from the centre of the municipal road and then with a spacing of 200 m between rows. A roadside belt is also in the sketch running east-west 90 m to the north of the highway.

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