Creating Microclimates With Windbreaks
Windbreaks — whether an evergreen tree, perennial grasses or other — are very useful in creating beneficial microclimates that allow for better crop yield.
By Ron Macher
In Making Your Small Farm Profitable (Storey Publishing, 1999), Ron Macher shares proven methods for farming smarter and explores today’s new crops, new livestock, and new markets that translate into new ways to make money. He explains how to capitalize on lucrative niche markets that others overlook, plan for optimal farm efficiency, compare costs against profit for common vegetables and livestock, sell your products a dozen different ways and more. In the following excerpt from chapter 5 discusses planting living windbreaks — trees, grasses or other — to give farmland protection from the elements and increase crop yield.
You can purchase this book in the GRIT store: Making Your Small Farm Profitable.
Creating a Microclimate
You cannot change the weather, but you can modify its effects by creating microclimates. A beneficial microclimate is an area that is protected from the worst effects of wind, weather, and temperature. It often tends to stay frost-free when surrounding areas are not, or it may offer protection from a hot sun in July.
Examine your farmland to see if you have any natural microclimates. These will be sheltered areas, possibly in a depression where the wind does not blow (although depressions often suffer from frost problems) or on a low hillside that is not as affected by wind or frost. If possible, walk over your property on a frosty morning in late fall or early spring and see if any areas are less affected — or not affected at all. These will be good places to utilize. You may wish to modify them further, to enhance the effect.
A little record keeping goes a long way. Buy a soil thermometer and test soil daily. Common plants such as lilac enter the first leaf and first flower stages of growth at specific temperatures and weather conditions. Checking temperatures and dates, and comparing these over the years, will make your farm more successful.
If there are no natural microclimates, create your own. In planning a microclimate, the best place to start is with a windbreak, which I will discuss in more detail in the following section. The windbreak controls a large microclimate, which sets the stage for a more subtle microclimate in your garden or planting area. Keep the ground protected, for example, with plastic or straw, to create a warmer environment for seedlings, hold extra water, and reduce weeds. (I tend to avoid plastic because it creates a mess when it breaks down; straw, on the other hand, breaks down into extra organic matter.)
Air flows just like water and settles in low spots. A raised bed might be just high enough to keep plants away from frost. Raised beds also provide warmer soil temperatures in the spring, sometimes by as much as 5 to 10 degrees.
It is also possible to create a microclimate for an individual plant by use of season extenders or similar tools. Research by D. R. Paterson and D. R. Earhart at the Texas Agricultural Experiment Station reported that when tomatoes were grown in black plastic with cages and then the bottoms of the cages were wrapped with common roofing paper, losses due to wind and hail decreased by 46 percent. After 5 weeks, there was a 62 percent increase in growth, with 86 percent more marketable fruit and a 49 percent increase in total yield. This data may not apply to all tomato varieties, but the method is worth a try if you have a wind problem early in the season.
Windbreaks and Sustainability
Principle: Plant or create windbreaks to prevent heat and moisture loss.
Wind can be a problem, as it leaches heat and moisture from crops and livestock. Therefore, crops and livestock protected from wind use moisture and nutrients more efficiently. One way to remove wind as a problem is through a windbreak.
Windbreaks reduce wind velocity, slow wind erosion, and create microclimates. Soil particles move when wind speeds are 13 miles per hour, 1 foot above the ground. When wind flow removes fine soil particles from one field, organic matter and nutrients go with it, so you have to increase fertilizer input or accept lower economic production in your crops.
Decide where to plant your windbreaks based on the direction of the prevailing winds. In most areas of the United States, you’ll need to plant windbreaks to the north and west of the area you want to protect. There is more information on height, length, and density of windbreaks in the section that follows. In general, though, windbreaks should be at least 100 feet longer than the area you want to protect, to prevent wind from whipping around the windbreak edges. For home protection, windbreaks should be
100 to 150 feet long, located no more than 300 feet away from the house, yard, and outbuildings.
A wind velocity of 5 miles per hour is slowed to 1/2 mile per hour in the lee of a windbreak — a 90 percent decrease. A 30-mile-per-hour wind will be reduced by 50 percent, to 15 miles per hour, by a windbreak. The lee can be a distance of up to thirty times the height of the trees (see next section).
University research shows that heat energy savings of up to 40 percent are possible when you use windbreaks. One study showed that a house with a constant temperature of 70 degrees Fahrenheit protected by a windbreak requires 23 percent less fuel than a house exposed to the full sweep of the wind. Permanent windbreaks on 40-acre fields at the University of Nebraska’s Mead Research Station increased soybean yields by 18 percent, corn yields by 20 percent, and wheat yields by 22 percent.
Windbreaks are a worthwhile investment. James R. Brandle, Bruce B. Johnson, and Terry Akeson, in a University of Nebraska study, found that “a full windbreak occupying 5 percent of the field is economically viable” and will “more than compensate for the cost of establishing the windbreak and the loss of output from acres taken out of production.”
Kinds of Windbreaks
To determine the best kinds of trees for windbreaks, consult your local university extension office or state Department of Agriculture. You will choose trees based on their lifespan, density, growth patterns (for example, evergreens do not shed needles, and thus provide more protection later in the year), and height. Trees or shrubs can be planted in single rows or in mixed groups.
Height. The height of a windbreak determines the protected area. A rough formula predicts wind speed reductions in an area of 2 to 5 times the height of the windbreak on the windward side and up to 30 times the height on the leeward side. This means that with 30-foot trees, the protected zone spans 60 to 150 feet on the side the wind is coming from and up to 900 feet on the side away from the wind.
Length. The length of the windbreak determines the amount of area receiving protection. According to windbreak expert James Brandle, the maximum efficiency for windbreaks requires that the length be 10 times the height.
Density. Varying the density of the windbreak can influence what you do with it. For instance, 25 to 35 percent density is best for even spreading of snow across a wheat field but will not control soil erosion as well as a 40 to 60 percent density. Evergreen trees, among them Eastern Red Cedar, are fairly dense. They are good choices for windbreaks because they don’t lose their needles in wintertime, unlike deciduous trees (broadleafs) such as oak.
The main advantages of tree windbreaks are their height (30 to 50 feet) and longevity (50 years). Trees are not the only windbreak materials, however. Perennial grasses and legumes can also be planted in strips. As well, small grains like rye, wheat, and oats can be planted in strips to slow wind erosion, conserve moisture, and provide a suitable microclimate for vegetables that need more wind protection, such as onions and early-planted cole crops. Corn rows planted in a field of soybeans or wheat grass in wheat fields are also beneficial. Two rows of corn are usually alternated with sixteen rows of soybeans or four to sixteen rows of corn and soybeans are planted in alternate strips.
Wheat grass is planted in double rows spaced 36 inches apart, every 48 feet across the wheat field; wheat grass grows about 5 feet tall. Annual plant windbreaks can be placed around an area perpendicular to the prevailing wind direction, just as with trees. In most areas of the United States, this means placing the windbreak on the north and west sides of the area to be protected. If there is no predominant wind direction, Laurie Hodges and James R. Brandle recommend planting annual windbreaks with the rows closer together, following the land contours or in a serpentine pattern, to slow the winds and protect the other plants.
Strips of small grains can also be used as lures to keep insects away from your cash crop. Insects prefer the small grains and will remain in them, rather than eating other crops. It is suggested that the strips of small grains be 45 to 60 feet apart in your field and of a width appropriate for your equipment.
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Excerpted from Making Your Small Farm Profitable (c) Ron Macher, line drawings by Chuck Galey, used with permission from Storey Publishing. Buy this book from our store: Making Your Small Farm Profitable.