- Vegetables: eggplant, greens (leafy), peppers, tomatoes
- Crop Production: greenhouses
- Energy: energy use
The problem this project was designed to address was: how early warm season vegetables can be produced to extend the growing season on the front-end by using low energy input, a greenhouse and other season extension techniques to offer produce for higher-value specifically to the early season market. We planned to convert an existing ornamentals coldframe to an inflated double layered hoophouse with additional internal row covers with a targeted transplant date in early April 2009.
Our farm is at 3,000 feet in the northwest mountains of NC where we have recorded a frost every month of the year except August. Our average frost free growing period is from May 15 thru September 27 giving us a narrow window for growing warm season crops.
Our local Farmers’ Market allows only produce and plants grown in our county to be sold at the Market. The existing produce growers all hit the Market with the same staple produce at the same time. This keeps prices down due to large quantities of the same staple vegetables. We want to offer our vegetables earlier so we do not contribute to the glut and price reduction and we want to support the market by enticing customers earlier in the season with a broad variety of quality fresh produce. Also by offering traditionally later season produce earlier we will be able to realize a premium price and support the sustainability of our farm.
Warm-season produce generally does not appear at our market until late-July and is not available in large quantities until August due to our colder climate. This leaves our Market customers waiting and drooling for most of the summer for their first ripe tomato!
With this project we hoped to learn the best methods for protecting tender plants from cold and freezing without supplemental heating so we can offer this to our produce mix by late June.
This project used an existing greenhouse that had been used to over-winter ornamental plants. It was covered with 1 layer of white one season poly (plastic). We replaced this with 2 layers of clear, non-drip greenhouse plastic one of which was an infra-red retentive poly. The 2 layers were separated by a layer of air circulated by an inflation blower. Irrigation was provided with drip tubes with 18″ spacing with emmiters rated at 1GPH. The greenhouse had 3 growing beds in it: 2- 3’x 95’ and one 7’x 85’ with 1.5’ aisles. The beds were covered with low-tunnels for the test, either agribon+ 30 or clear 6 mil. plastic to provide an additional level of freeze/ frost protection. Other plants were protected with only a wall-o-water. The soil surface was covered with IR retentive plastic or woven black fabric. We placed maximum/minimum thermometers and soil thermometers under each type of protection for each type of vegetable planted. We recorded both inside and outside temperatures daily. This data was collected until the plants outgrew their protection. We were able to collect the data for 4 weeks, from early May through early June. We planted 1 variety each of tomato (88 plants total for two varieties), pepper and eggplant (44 plants each) so there were enough plants for the test repetitions.
The test involved 11 plants of each vegetable under each type of protection plus 11 control plants of each. Though the control plants were not expected to survive they did so we did not have to replant that area with greens as we had expected. We measured the growth of select plants weekly, recorded when they flowered, set fruit and when the fruit ripened. We kept track of when we had the first saleable fruit and how much weight we sold from the plants in the study during the growing season. This was done for each type of protection and vegetable type involved in the study.
The plants were grown under their respective covers with the planned addition of a very heavy spun-bonded fabric we already had on site which would have been used to cover the rows if the nights got extremely cold. This added layer was not needed in 2009.
We amended the soil as indicated by a soil test and planted a cover crop of annual rye for November through February 2009 to prepare for 2010 crop. We talked with a nearby worm farmer about using worms to aerate the soil in our greenhouse. He said we should be able to keep the worms in the greenhouse beds so we began a worm population by adding 2 pounds of worms per bed.
The plan for this greenhouse also included planting a vegetative farmscape border down one side to attract beneficial insects and offer “trap” alternative plants for insect pests. Because of our existing ornamental and cut flower operation, this farmscaping was deemed unnecessary.
All of the transplants for this project were produced on site in our heated greenhouse. They were ready to transplant into the test greenhouse by early April.
The bed space in the greenhouse not planted in plants for the research were planted in lettuce, spinach, endive, and mache for the early market. These vegetables proved to be excellent sellers for us last season.