Virginia Vegetable, Small Fruit and Specialty Crops
September 2002; Volume 1, Issue 9
Charlie O'Dell, Extension Horticulturist Emeritus, VA. Tech
Over this region and much of the eastern USA drought has continued to plague growers. Water supplies have dwindled or dried up on many farms. Surface water from ponds and streams has not been available for irrigation.
Assuming rains come to replenish irrigation sources, how can growers plan for future water conservation measures so they can extend their water resources in coming years? For example, let's think about our water needs for both strawberry frost control in bud and bloom next spring, plus our increasing need for evaporative crop cooling in sudden extremely hot weather above mid-80's F. during strawberry bloom, fruit set and harvest.
For many of us now facing diminished water supplies, how can we use less water, even less pumping energy, but still optimize fruit set, fruit quality and obtain more profitable and longer season yields? Not enough has been written to date on the subject, but we've noted that innovative growers succeeded last spring under very trying weather conditions that had it all: Too hot too early, then too cold later after plants flushed out with new tender spring growth including buds and blooms, then too hot at harvest, with wild temperature swings throughout the whole spring. For most growers it was a spring we would just as soon forget!
How did these few successful growers profit last spring under such adverse conditions? They went to the use of low impact type of low volume, low pressure (30 lbs psi) sprinklers in combination with crop covers that got them through some amazingly low temperatures during bud and bloom. This technology was first tested by Dr. Barclay Poling and associates at North Carolina State University at their Clayton, NC research farm's strawberry plots during previous spring freeze conditions. They saw the potential of this combination of covers plus low-volume non-impact sprinklers to provide greater frost and freeze protection, plus solid-set sprinklers for later crop cooling during harvest. They explained this combination system to growers from several states that attended recent SE Strawberry Expos held annually in North Carolina. Their next step was to involve growers with field tests, Extension demonstrations under growers' actual conditions. Dr. Allan Straw, Extension Horticulturist, University of Tennessee Knoxville, also was very helpful with frequent farm visits to such a test with a family in Tennessee. But, no one realized what nature had in store for the spring of 2002. Bad times were coming, quietly sneaking up on growers over the whole region. The stage was set for a very Real Test, several times, both with severe cold and severe heat!
low volume sprinklers may apply less water volume than can adequately provide sole frost/freeze protection via water's latent heat of transfer in extremely low temperatures with low dew points. So, crop covers were used beneath the sprinklers which allowed growers to ice-over the covers creating a warmer, protective "igloo effect" under the covers. Many growers continued to operate the low volume sprinklers over the iced covers (recommended), which, with the covers, further reduced threat of super cooling or freeze damage to crowns, buds and blooms. Those growers who ran water continuously in small volume over their iced covers even saved their berry crops down into single digit temperatures, and, the oscillating or wobbling action of the sprinkler heads prevented them from freezing up at these very low temperatures! Did I say no more knocking ice off sprinklers during operation in sub-freezing temperatures?! (Note: under single-digit temperatures, 18 inch riser height is recommended so ice has a place to build up beneath the constantly running sprinklers. Last spring, a Tennessee family ran this system over covers for 42 continuous hours at temperatures as low as 8 degrees F, and, successfully protected buds and blooms!).
In order to maximize this system for both frost protection early on and for crop cooling later in the spring, I noted some growers used small diameter pvc pipe with short risers laid down the bed centers. Then the system could be left in place all spring right through harvest without impeding foot or equipment travel. When hot weather came, they were able to provide excellent, low-volume evaporative crop cooling for short bursts several times during hot days. Crop cooling provided conditions to keep their plants in a fruiting mode for a longer period, and what a beautiful and longer season crop they made! By cooling plants with low water use, they were able to keep plants blooming and bearing, extending their harvest season way beyond others whose blooms were blasted by heat and whose plants' fruiting systems were shut down by the intense heat. It is rare when a new technology benefits berry growers on both ends of their spring crop season!
All I can say is that this system worked for them in the toughest spring berry season I have experienced in nearly 4 decades of berry growing. We all need to get out and visit some of these progressive growers and their irrigation and crop cover dealers. Ole Sachel Paige was right: If we look back, something was gaining on us! These are tough times, we salute these pioneering growers in Tennessee and North Carolina! Also, many thanks to Dr. Barclay Poling, Extension Strawberry Specialist, NCSU, for helping develop this technology, then documenting and detailing these innovative growers' experiences in recent strawberry growers educational meetings over the southeast region.
Visit
Virginia Cooperative Extension
