NANCY, Ky. — Joel and Beth have 10 acres of plasticulture strawberries in production and do an exceptional job of production and marketing. After the very wet 2017 season they purchased a new bed shaper and plastic layer. This equipment produces a very high crowned bed that does a very good job of shedding water, keeping the fruit dry and reducing fruit decay in a wet spring.
Dr. John Strang will discuss basic plasticulture strawberry production practices and Dr. Ric Bessin will discuss insect and mite control.
Your gps should take you right to the farm using the above address.
Bud/bloom protection vs. row cover removal
It looks like we will have a particularly early spring this year, strawberry growth has begun under floating row covers and some plants are beginning to bloom. Removing row covers allows more light to plants and additional early growth. Plasticulture strawberries are showing bloom in the southern and western parts of the state. Since the earliest blooms produce the largest fruit frost protection is extremely important. Consequently we uncover and recover fields based on the weather.
Reapplying row covers on short notice ahead of a severe spring freeze requires labor availability at a moment’s notice. Overhead sprinkler irrigation can provide additional degrees of freeze protection.
Below are some things to help with deciding when to apply and remove row covers:
The picture and table below are from Barclay Poling. Note the stages of bud development and critical temperatures. Keep in mind that these temperatures are taken in the plant crown, where the temperatures can be several degrees cooler than the low temperatures provided by the National Weather Service that are taken at a five foot height.
In the transition period from dormancy to new leaf growth stage, there is still considerable hardiness in flower buds, and it is definitely possible for an emerged flower bud, but not flower bloom to tolerate temperatures below freezing, especially if it is a recently emerged, smaller flower bud. Note the two emerged flower buds above the pencil tip.
A medium row cover of 1-1.25 oz provides about 4-6 degrees of protection.
For a crop that is starting to come out of dormancy (new leaf growth, some buds visible/emerging) a single row cover of about 1-1.25 oz will protect tight buds
For a crop out of dormancy, open blossoms and popcorn stage buds will not be protected adequately if it gets down to 22 F, with a single cover
Growers that have extra covers should consider applying a second cover over the first for added protection if particularly low temperatures are predicted. Growers that have overhead sprinkler systems for frost protection benefit from applying water on top of the row covers for considerably more frost protection.
Several things work for or against flower buds/blooms when a freeze is forecast:
Daily temperatures a few days prior to the forecast freeze – cooler days will make developing blooms and blooms more hardy. Colder temperatures this week and forecast for next week should harden plants off to some extent, ahead of cover removal.
Soil temperature – warmer soil has more heat to give off, protecting blooms
Soil moisture – wet soil also helps provide a little more heat, so rains prior to a deep freeze can help protect plant tissue.
Humidity/dewpoint – as moisture in the air freezes, it gives off heat that helps protect plant tissue. A high dewpoint means there is a lot of moisture in the air, and therefore more heat to be given off as the temperature drops and this slows the rate of temperature drop.
Types of freeze events
A radiation freeze occurs on still nights. Heat in the plant, soil, and surrounding air radiate upward, and the plant tissue basically freezes due to heat loss, as opposed to being frozen by cold air being brought in by wind, which is an advective freeze. The higher the dewpoint is during a radiation freeze, the longer it takes for the plant tissue to freeze. This is due to the heat of fusion (heat given off when water “fuses” into ice) given off by moisture in the air. Usually, with a radiation freeze, the lowest temperature of the night is just before sunrise. It is here that a row cover may buy just enough extra time to avoid plant damage.
An advective freeze occurs when a cold polar front blows in very cold, often dry air. In such cases, heat of fusion during freezing is minimal. Row covers may help for a very short time.
Saturday March 24, 2018
Wilson’s Cedar Point Farm
66 Garfield Tarter Rd
Nancy, KY 42544
10:00 a.m. EDT
— University of Kentucky
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