Winter Time Woes: Frost And Freeze Protection Options For Farmers

When I first wrote this post, weather forecasters around the U.S. were watching for what was expected to be a highly impactful, significant winter storm. And now as I enter this update, it turns out the forecasts weren’t overblown. The massive winter storm delivered — and then some — to a vast expanse of the country. How bad was this winter storm? AccuWeather experts are saying the extreme weather event could result in $105 billion to $115 billion in total damage and economic losses.

Though the storm might be gone, winter is far from over. For this week and into the weekend, extremely cold temperatures are expected to lock in and deepen across much of the country. Areas of the South — all the way down into Florida — won’t be safe from frost and freeze events.

Farm operations of all kinds prepare in advance for these kinds of conditions. Taking precautions ahead of the storm can limit the downtime  afterward.

About 10 years ago, we published a piece where experts offered advice on how fruit growers can combat cold temperatures. Consider this reference a tip of the cap to the current “Reliving 2016” trend running amok on social media.

One of the contributors to the piece back then included Mary Concklin, Extension Educator Emeritis from the University of Connecticut. She provided several frost/freeze protection options for produce growers. The pointers offered then still have value today.

Here are her frost/freeze protection options for growers:

Row Covers

Row covers are spun bonded polypropylene and vary in weight from 0.45 ounces to 4 ounces. Cloth sheets also work for small areas. Research has shown using two layers of a 1-ounce weight row cover provides somewhat better frost protection than a single layer of 2 ounces cover, likely due to air between the layers. Heavier covers (3 ounces to 4 ounces) work for frost protection but restrict light too much and need to be removed as soon as temperatures are above freezing. Be sure to anchor the row covers for the winds. If you have the swing arm trellis for blackberries, lower it to the ground and put the row cover back over it. A double layer where growth is already underway is advisable. Avoid placing plastic over the rows unless it is suspended and will not touch the plants. Wherever the plastic touches the plant — leaf or flower — the plant tissues will be killed in freezing temperatures.

Straw

Straw is a very good insulator, which is one reason it is used for winter protection of strawberries. If you have removed the straw from your strawberry beds, put it back on. Adding a row cover on top is an added measure of security.

Overhead Watering

Overhead watering works based on the principle of latent heat of fusion — as water turns to ice, heat is released. This heat maintains the plant tissue at just above freezing. If at any time during the night the water stops while the temperature is below freezing, the process reverses —heat is removed from the plant tissue and the tissue will freeze. To avoid this, watering must continue until the air temperature rises above 32⁰F and the ice has started to melt.

Overhead watering may be combined with the use of row covers or used independently and requires a calibrated emitter system to be sure the required amount of water is constantly being provided. Positives are a proven track record of maintaining the temperature of the flower buds above critical temperatures. The negative is that it may lead to saturated soils and root diseases; if the water stops at any point when the air temperature is below the 32⁰F, the buds will freeze; and limb breakage from heavy ice buildup.

Keep in mind, in a windy situation, you will not be able to maintain an even distribution of the water.

Under-Tree or Surface Watering

As the water cools, it releases heat into the environment around the trees and plants and also increases the relative humidity which reduces radiated heat loss. Advantage: the sprinklers do not need to be as precisely calibrated as they are for overhead sprinklers; if the system shuts down during the night the impact is not the same as with over-head watering.

Potential problems: saturated soils; increased root rot problems.

Wind Machines

This method carries an initial high expense, but on sites that are frost-prone this method will pay for itself. A temperature inversion and wind speeds less than 5 mph are required for this system to be effective. There are several models, mobile and stationary, tall for tree fruits and lower for vegetables and small fruits. Acreage covered varies by model and the strength of the temperature inversion, generally 1 acre to 20 acres. May be used in combination with supplemental heat for large areas, or when the temperature is expected to be down to the low 20s, or with a weak temperature inversion.

Helicopters

The aircraft utilize the temperature inversion the same as the wind machine. Their mobility is an advantage which enables them to cover several small frost pockets or one large area as long they return to the starting point every 4 to 5 minutes. The larger the aircraft, the more air it will move and the larger an area it will be able to cover. The larger aircraft will also be more expensive. These cannot be used in conjunction with any type of added heat that emits smoke for obvious safety reasons. Refer to the pilot for the types of lighting needed to mark the areas to be covered.

Return Stack Heaters

Heaters hold approximately five gallons of fuel with 20 to 40 heaters needed per acre, placing more on the upwind side of the block. They are effective when used alone as well as in combination with wind machines. Light every second or third heater initially and then light the rest. This will allow heat to begin moving through the field without a big burst of heat that may puncture the inversion layer.

Open-Burning of Straw bales, Wood piles, etc.

Avoid large fires (bonfires) as these will penetrate the inversion layer allowing the heat to leave the fruiting zone. When that happens, the only place there will be heat is right next to the fire. Small fires work best. Disadvantage of open burning — smoke. The smoke will hang over the field even after the sun is up but will not allow the heat from the sun’s rays to penetrate the smoke to warm the field keeping it colder longer. If the smoke is not there, it will have moved to your neighbor’s property. Be sure to check with your local fire department in advance for a burn permit. Don’t bother with tires — you will never get a permit for them.

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What frost/freeze protection practices work best on your farm? Share them in the comment section below.