Economics of shelterbelts

Growing shelterbelts has long been considered an effective practice to reduce soil erosion. Recent research also shows that field shelterbelts increase crop yields. It is thus now possible to plan for increased crop yields using field shelterbelts. Other benefits of shelterbelts are enhanced wildlife habitat and a more scenic landscape.

Although field shelterbelts will provide these yield benefits only when the trees are mature, the question arises, "Is it worth the effort and cost to nurse a shelterbelt through the first 10-15 years until the full yield benefits are realized?"

A model that evaluates the costs and benefits of a field shelterbelt through its lifespan has been developed by staff at the PFRA Shelterbelt Centre at Indian Head, Saskatchewan. Costs and benefits are determined from the time of planting the belts to the time of their removal many years in the future. Evaluation software is available to agricultural extension workers and to those producers who are equipped with IBM type computers. Contact the PFRA Shelterbelt Centr at Indian Head, Saskatchewan for information.

You can, however, determine the effect of mature shelterbelts by performing a few simple calculations which can then be used in a partial budget exercise. The calculations used in this exercise are based on shelterbelt designs recommended by the PFRA Shelterbelt Centre at Indian Head, Saskatchewan. Using other designs may alter the projected figures in this exercise.

What is a Partial Budget?

Partial budgets are useful planning tools for deciding how a change in a specific farming operation will affect farm costs and returns. Partial Budgeting is defined as the process of examining only those costs, returns and resource needs that change with a proposed adjustment. The cost, returns and resource needs of the business that are not affected by the proposed adjustment are ignored.

In performing the partial budget for shelterbelts, you weigh the advantages against the disadvantages of the proposed change. Advantages resulting from the proposed change would be added revenue and/or reduced costs. The disadvantages to the proposed change would be any added costs involved in adopting the change, or any reduced revenues that would result from the change.

Assumptions Involved in Calculations

Shelterbelt Design

Shelterbelt design will vary by area and objective. The three most common shelterbelt designs on the prairies are single row green ash, caragana and caragana green ash combined. Two other possible shelterbelt designs here are Scots pine, and multi-species multi-purpose shelterbelts primarily for wildlife habitat. Shelterbelt characteristics have been determined through research conducted by the PFRA Shelterbelt Center, Indian Head, Sask. are listed in Table 1 (page 10).

Shelterbelt Effect on Crop Yields

Research throughout the prairies has found that crops grown in fields protected by shelterbelts will yield better than crops grown in unsheltered fields. This is due to many interacting factors including less soil erosion, lower wind speed and evapo-transpiration and higher temperatures. For the five shelterbelt designs, the base yield increase (in percentage) for wheat is listed in Table 2 (page 10).

Moisture Stress Factor

Shelterbelts give greater percent yield increases in areas where water is a limiting factor than in areas where water is not usually a problem. The benefits also depend on soil texture, which affects the water holding capacity of the soil. The more water a soil can retain, the better the crop yield. When calculating yield increases due to sheltered crops, there must be an adjustment to the calculation that takes into account soil texture and water availability. This adjustment has been determined through research on the prairies. It is called the Moisture Stress Factor. The factors for the common soils on the prairies are given in Table 3

Crop Response Factor

Crops grown on the prairies are somewhat different in their natural ability to grow under sheltered conditions. Sensitive crops like sunflowers or canola will benefit more from sheltered growing conditions than drought-hardy crops like wheat. When calculating the yield benefits for crops grown under sheltered conditions, an adjustment must be made to compensate for these differences. These adjustments are called the Crop Response Factor and are given in Table 4.

Using these assumptions work through the following five steps in preparing the partial budget to determine the economic effects of having mature shelterbelts on crop land in a typical year.

This publication is one of a series intended to help producers assess the economic benefits of implementing conservation practices into their operation.

Worksheet 1

Step one- Calculate the added annual revenues resulting from increased crop yields grown on fields which are protected by shelterbelts.

Worksheet 2

Step two - Calculate the annual cropping costs saved due to having land occupied by shelterbelts instead of crops.

Worksheet 3

Step three- Calculate the added annual costs of maintaining the shelterbelt.

Worksheet 4

Step four- Calculate the annual crop revenue that is lost due to having land occupied by shelterbelts instead of crops, and tree root competition with nearby crops.

Worksheet 5

Step five- After performing the calculations in Steps 14, the disadvantages of the proposed change (added costs and reduced revenues) are subtracted from the advantages of the proposed change (added revenues and reduced costs). The resulting net change will give you an indication whether the proposed change of adding shelterbelts to your farm operation will be beneficial once the trees are mature.

Appendix

The appendix information is intended as a guide for worksheet calculations. Use your own figures if they are accurate or check with your local Extension Agrologist/Conservationist office to determine if more accurate data is available from local research or demonstartion projects.

SUMMARY

Designing and implementing a field shelterbelt system for your farm can yield positive economic return in the long run. Aside from the economics of growing crops near shelterbelts, there are other factors to consider when deciding to incorporate shelterbelts into your farm operation. Such considerations are as follows:

1. Shelterbelts must be established carefully to ensure their survival through the critical first years. In order to ensure the shelterbelt makes it through these first few years, the planting site must be carefully prepared so weeds do not crowd out the young seedling trees. Weeding in the first several years is essential to the trees' survival; you must be prepared to take some time for herbicide application, tillage next to the belt, and hand hoeing within the rows. The better your shelterbelt can become established, the sooner and better it will protect your crops in the future. The costs of these operations are taken into account when using the computer program available through Extension Agrologists and Soil Conservation Offices. To obtain a complete analysis of the cost/benefit of field shelterbelts, you should perform the computer calculations. See your area conservationists for more details.
2. Tillage for weed control is quite common alongside shelterbelts. A tilled strip approximately six feet wide along both sides of the trees is adequate to protect the young trees from weed competition. If you do not have this type of equipment, you should budget for a small tractor, six foot disc or cultivator, and probably a three point hitch or small tow type sprayer.
3. Check with your local ADD board or PFRA Area Soil Conservationist regarding any programs available offering assistance to producers who wish to establish new shelterbelts. Many groups are now providing incentives for planting and maintaining trees and a few will provide these services for the first three years at a nominal fee.
4. The type of analysis done in this publication will show you the economic costs and returns of having mature shelterbelts. There are other benefits that you will receive which are difficult to quantify.
   Shelterbelts protect fields from wind erosion and topsoil losses. This not only relates to the soil's productivity, but also provides peace of mind when strong winds start other fields blowing.
   Wildlife benefit from the habitat shelterbelts provide. Many birds and animals will use shelterbelts for protection from predators, transportation corridors and food sources. Careful planning of shelterbelts will actually attract certain birds and animals to your farm.
   The decision to implement a shelterbelt system in your operation can best be made after the advantages and disadvantages are evaluated. Field shelterbelts may well be a practical alternative for your farm.

The PFRA Shelterbelt web site contains additional information about the value of shelterbelts and software you can download to assist you in assessing the economic benefits of establishing shelterbelts.

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