By Natalie Euler
Forester, Northwest Area Conservation Districts
There are several keys to successful shelterbelt establishment. Select the right site and location to accomplish the intended purpose. Evaluate the soils map and slope conditions for site limitations. Design the orientation and length, so as to protect the intended area without causing problems in adjacent areas. The planned width between rows should be suitable for tree species and the equipment to be used for maintenance. Select species that are proven to do well on the soils, growth rates to provide protection soon enough, mature heights to protect a big enough area and longevity for dependability for the future. Make plans for long-term weed control by using mechanical methods, mulches and chemicals.
Site preparation for shelterbelts is very important. The best time to begin weed control is prior to planting. Perform deep tillage 9”-12” deep one year prior to planting to reduce weeds and bank soil moisture. Clean cultivate the site and / or use herbicides to keep the site weed free. Limit spring tillage to a light disc or harrow to remove new annuals and save moisture.
When designing and selecting species for shelterbelts, plan for five or more rows for primary protection from the north and west and two to three rows for secondary protection from the south and east. Include at least one row of evergreen species and at least 1 row of fast growing broadleaf species. Ensure that snow accumulation does not crush or break down leeward rows by planting tree and shrub species that are best suited for leeward rows. It is important to select species that are adapted to our area and USDA Hardiness Zone.
Good care and maintenance of your shelterbelt will result years of good service. Weed control and soil moisture retention are critical and related to long-term survival. Weeds can use most of the available moisture and greatly reduce tree seedling growth and survival. Mechanical weed control is very effective at bringing weed seeds to the soil surface for germination and controlling annual weeds. Several cultivations during the growing season are best. Care should be taken not to cultivate too deep as tree roots may be damaged. Perennial weeds should be sprayed with herbicides and allowed time to die before cultivation.
The use of weed control fabric has become very common with shelterbelts in the last twenty years. It acts as a physical barrier to weed emergence, prevents sunlight from reaching germinating weed seeds and conserves moisture. It is important to either do tillage or mowing between the rows several times during the growing season. Otherwise, weeds can grow big with roots reaching underneath the fabric robbing moisture from the trees.
Herbicides can be used to effectively control problem weeds, especially perennials. Use of pre-emergent and post emergent herbicides along the edge of weed control fabric eliminates strips of weeds left from tillage and it is possible to eliminate weeds between trees and growing through the slits next to the trees. It is possible to control many annual weeds and save some moisture with pre-emergent herbicides without the use of weed control fabric in the rows of shelterbelts. A 4 foot wide band of herbicide is sprayed directly over the row after the killing frost in the autumn when trees are dormant. After 4-5 years and the trees are established and too big to spray over, use of pre-emergent herbicides can be stopped.
Shelterbelts can be damaged by livestock and upland wildlife. Construction and maintenance of appropriate protective fence should be done as needed. In some situations the use of tree protectors and wildlife repellents may also be warranted.
My sources for this news release were the Montana State Seedling Nursery and Natural Resources Conservation Service. If you would like more information about “Shelterbelt Planning, Establishment and Maintenance,” call Natalie Euler at the Conservation Office at 605-244-5222, Extension 109 or email [email protected]