A textile cover laid directly over strawberry plants helped them produce more than three times as much fruit in tunnel field trials, with no sign of harm to the plants themselves.
The fabric, called Plant Armor, has a three-dimensional structure that forms a barrier insects cannot cross, while the layered material still lets sunlight, rain and air through. In the trials, covered strawberries yielded as much as 3.56 times more than uncovered plants.
The cover did not reduce the light reaching the plants, and did not affect relative humidity.
That surprised the team. "To produce fruit, plants need sunlight," said Gabriel Olawuyi, a graduate research assistant at North Carolina State University and lead author of the paper. "We expected that Plant Armor's seemingly opaque fabric would lead to an increase in vegetative biomass at the expense of fruiting -- because reduced sunlight would trigger a 'shade-avoidance' response, making the plant divert energy toward stem and leaf growth rather than fruit production. However, we found the fabric did not impede access to light at all, and fruit production increased significantly."
The researchers also found that the cover produced a steady warming effect across all three growing seasons, and that the extra warmth brought the covered plants to the fruiting stage earlier than the uncovered ones.
"Plants require a certain amount of accumulated heat, calculated as 'growing degree-days,' to progress through developmental stages including fruiting. Our plant cover has proven to enhance these," Olawuyi said. "The plants were in a condition whereby the warmth they need to go through each phenological stage to their production was given to them optimally, and they produced far more than the uncovered plants."
Because the fabric physically stops insects feeding, the team says it could also cut the quantity of conventional pesticide needed, and reduce water use.
The idea did not start in a field. The technology came out of work on making military uniforms more resistant to mosquito bites and on making body armour more comfortable to wear.
"The path to Plant Armor started with trying to make a cloth to go on a soldier's chest to make body armor more comfortable," said co-author R. Michael Roe, William Neal Reynolds Distinguished Professor at NC State. "Then, through trial and error, we arrive at a product which could triple the output of strawberry farms here in North Carolina."
The paper, "Knitted 3-D, Porous Textile Cover to Enhance Strawberry Fruit Production and Prevent Insect Feeding", is published in the journal Agriculture. The Plant Armor Gen 2 fabric is patented by North Carolina State University and licensed by it for commercial development.
The finding, stated plainly, is that a barrier built to exclude insects tripled the harvest by keeping the plants warm. The insects were the design brief. The warmth was a side effect of the knitting.
This newspaper draws the obvious inference. The limiting factor on strawberry production in North Carolina was not pests, water or sunlight, all of which were present in sufficient quantity under the fabric. It was that the plants had nothing to wear.
The vocabulary supports the reading. Growing degree-days are an accumulated heat requirement, which is to say a plant's annual warmth budget, and the trials show it can be met from outside by the simple expedient of a coat. The strawberries were not underfed for three growing seasons. They were underdressed.
This also explains the origin of the material. Nothing was repurposed. A garment designed to keep a warm-blooded body comfortable was placed over a cold one, and performed its original function without modification.
The Department of Unnecessary Research regards the agricultural application as settled and the economic one as urgent. North Carolina has established that output triples when the crop is properly clothed, and nobody has yet checked whether the effect holds for the farmer.