Most of the dense tall trees are not lovely to look at, but they do protect when that wind comes howling across the plain:)
http://agriculture.kzntl.gov.za/portal/publications/production_guidelines/conservation_farmland/cons_farm_2.9.htmHE VALUE OF WINDBREAKS
The systematic planting of windbreaks on a farm brings the following benefits to various farming enterprises:
* wind speed is greatly reduced, preventing physical damage to flowers, fruit and plants by dust, hail, snow and abrasion. Both the quantity and the quality of the crop is improved by the planting of windbreaks.
* The pernicious damage by wind erosion to the soil resource, which results in a lowering of soil fertility, is reduced,
* Lowering wind speed reduces the chill factor, resulting in higher stock survival,
* Lower wind speeds reduce evapotranspiration, resulting in more efficient use of available soil moisture,
* Low wind speeds facilitate pollination by bees, which is important where grain or fruit is produced,
* Shelter is provided for desirable birds and animals,
* Protection from wind prevents lodging of crops such as maize,
* Windbreaks can supply products such as timber, poles and firewood and provide nectar and pollen for honey production, and
* Windbreaks add to the attractiveness of a farm.
Figure 1. How a windbreak works
While many of the advantages of windbreaks are intangible or difficult to measure, the following direct benefits have been reported:
* In Denmark crop yield was increased 4,5 times more than what was sacrificed in providing shelter,
* In the United States the leafage of maize increased by 90% and the grain yield by 100 to 150%, while under drought conditions lucerne protected by windbreaks produced up to three times the yield achieved without windbreak protection, and
* Windscar blemishes in citrus can be reduced from 40% to 10% by providing suitable windbreaks. This has a very large economic significance to the exporter.
It is estimated that 5% of a farm can be planted to windbreaks without reducing the overall yield.
DISADVANTAGES OF WINDBREAKS
* Windbreaks planted on the contour can trap cold air (resulting in frost pockets), or hot air (resulting in heat scorch), both of which can cause crop damage.
* Windbreaks running east-west will shade the southern side all day, reducing crop growth and slowing down the drying out of roads and poorly drained lands after rain.
* Land which would otherwise be under crops is taken up by trees.
* Tree roots can affect the productivity of the adjoining land for a distance of approximately their own height. This effect can, however, be greatly reduced by annually ripping a single deep line parallel to, and 3 to 4 metres away from, the tree line to keep tree roots away from the crop.
* Undesirable birds, such as finches, find shelter in windbreaks.
* Too dense a barrier can result in winds becoming turbulent in the lee of windbreaks, causing physical damage to crops.
* If the wrong tree species is chosen it may invade adjoining areas.
snip