| |
return to Farmers Independent Weekly
September 23, 2004
by Bill Remphrey, Department of Plant Science |
Is it time to take another look at shelterbelts?
Most of us take field shelterbelts in the prairie landscape for granted but many farmers are now in the process of eliminating them because they do not fit well into the scheme of modern agriculture. Admittedly, field shelterbelts take up space and thus remove land from production, compete with adjacent crops, get in the way of large machinery and require labour for establishment and maintenance. So what is the place of shelterbelts in modern agriculture on the prairies? How can we assess their value? Let’s take a closer look at field shelterbelts.
Shelterbelts have been used world-wide for centuries and the concept of sheltering fields and farmyards was imported by settlers as they arrived to homestead the prairies. They quickly saw a need to protect their homes, livestock and themselves from the ravages of the prairie winds. A shelterbelt nursery was established at Indian Head, Saskatchewan in 1901 and trees were distributed to homesteaders, primarily for use around their homes.
 The use of field shelterbelts on the prairies peaked in the 1930s when an economic downturn was accompanied by the severest drought yet experienced in the region. Because of the way in which the land had been broken and the management practices of the day, the soil was exposed to serious wind erosion. This consequent passing of the Prairie Farm Rehabilitation Act established demonstration field shelterbelt systems in various locations including Conquest, Saskatchewan, and Lyleton, Manitoba. The value of these belts soon became apparent in halting soil erosion and extensive field shelterbelt planting occurred in earnest. Planting of these belts has waned in recent years however, and demonstration shelterbelts dating back to the ‘30s are now being removed, partly because of a change in management practices, but also because the shelterbelts are declining. So, given the changing nature of agriculture and the negative aspects perceived to be associated with shelterbelts, are shelterbelts still relevant?
A survey in the late 1980s (Laughlin, K.M. 1989. Attitudes of Montana and North Dakota landowners regarding the condition, management, value of windbreaks. M.Sc. Thesis, Dept. of Horticulture and Forestry, NDSU, Fargo, North Dakota) revealed that wind erosion is still the number one reason why field shelterbelts are planted in Montana and North Dakota. Drought conditions of the past few years in many parts of the prairies have rendered the soil less stable, even under reduced tillage, because of soil dryness and minimal protective crop cover.
In addition to the potential importance of field shelterbelts for reducing soil erosion, there are other compelling reasons for retaining or planting shelterbelts. Shelterbelts can increase crop yields by up to 45% depending on the crop and the environmental conditions present (Kort, J. 1988. Benefits of windbreaks to field and forage crops. Agriculture, Ecosystem and Environment, 22/23:363- 380). The trees influence the micro-climate for the crops and the resulting changes in temperature, humidity and reduced desiccation are transmitted to the growing crop. Moreover, protection from the wind results in less damage to the plants themselves. Besides an increase in yield, for some tender horticultural crops like strawberries on the prairies, the use of shelterbelts is virtually a necessity. Thus, shelterbelts are important when considering crop diversification.
Despite these studies however, many farmers remain skeptical. A Kansas survey, (Cable and Cook, 1997. Farmer’s attitudes and behaviors toward shelterbelts in Kansas. Proc. wind erosion: an international symposium, Manhattan, Kansas) found that only 8% of respondents believed that increased crop yields were a benefit of shelterbelts!
Interestingly, although the value of shelterbelts is not well understood, the concept of multiple-use shelterbelts in fields and around farmyards seems to be gaining popularity. In Kansas, Cable and Cook (1997) found that almost two thirds of the respondents planted shelterbelts for increasing wildlife habitat. This is particularly true of multiple row shelterbelts which can increase the diversity of birds, small mammals, beneficial insects and microorganisms as well as plant materials including mushrooms, fruit bearing plants and wildflowers. These shelterbelts are multi-purpose. In addition to the shelter, they are a source of fruit and nuts and value-added products such as fruit jams and syrups, as well as maple syrup, firewood, lumber, and game.
Shelterbelts are being used in some parts of the Canadian prairies and the Great Plains of the US to protect livestock from the harsh winter winds. Improved animal performance has been reported. Such shelterbelts can be a potential source of shade in summer months as well.
An additional benefit of shelterbelts for livestock operations is their role in the control of odours. Shelterbelts cause air to be forced upwards, creating turbulence that research suggests will help dissipate and dilute livestock odour. As well, slowing the wind on the lee side of the belt may help to settle out some of the odour particles so they cannot travel downwind. This has been shown with respect to dust control and snow filtering. And - shelterbelts may actually intercept and absorb some of the odour causing molecules. Considerable research has shown that trees are capable of intercepting and absorbing air pollutants in general and research is continuing on their role in odour control. An in-depth report on this subject by is available on the web (Tyndal, J. and Colletti, J. 2000. Air quality and shelterbelts: odor mitigation and livestock production, a literature review. Iowa State University, Ames, Iowa).
Finally, shelterbelts may be important for sequestering and storing carbon to help alleviate carbon dioxide emissions into the atmosphere. Some estimates consider that a typical tree may be 40% carbon. There is considerable effort to try to quantify the amount of carbon stored in shelterbelts. Preliminary results from the Shelterbelt Centre in Indian Head, Saskatchewan, indicate that they may store more carbon than previous models have predicted. However, the long-term significance is yet to be determined.
Shelterbelts in the prairie landscape can do many things, including protect soils, crops and livestock from the wind, intercept air borne materials, fix carbon, produce secondary products and beautify the landscape. They do indeed deserve a second look!
|
|
