Final Report for FW07-319
A moveable hoophouse was used to test the difference between protected and non-protected crops on plots of 24’ x 32’. Treatments included two plots for perennials and three plots for annuals, which allowed a rotation to a cover crop. Annual crops that especially needed protection from killing frost and warm nighttime temperatures, including tomatoes, winter greens, long beans and okra had significant increases in production. It was more difficult to determine benefits for perennials chosen. Asparagus avoided a spring freeze that would have killed plants back to the ground, which significantly increased production; and raspberries, due to establishment problems, will produce the first mature crop the 2010 season.
The purpose of the Moveable Hoophouse (HH) project was to determine how to manage a protective structure that could benefit more than one or two crops in a year. The project addressed one of the two biggest problems that an organic farmer/gardener faces; the vagaries of weather. Weeds seem, like our crops, to be quite happy to be protected from the elements.
The 24’ x 32’ HH was designed with a set of runners on which to slide from plot to plot, with five trial and five adjacent control plots.
The objectives of the project were:
• To demonstrate that a single structure could be used to protect several crops at different times of the year on different plots of land.
• To extend the season of production, and thereby increase the employment opportunity for the farmer.
• To do local, regional and interstate outreach to show the potential of this idea to others.
Two sets of five 24’ x 32’ plots were laid out running sequentially from west to east, with the first three sets of plots rotated among tomatoes, peppers, and basil; various winter greens; and heat-loving summer crops of long beans, okra, etc. The fourth pairing of plots was raspberries, and the fifth set was asparagus.
A 24’ x 32’ gable-roofed hoophouse (HH) was fitted with runners made from 2” x 2” boxed steel tubing, which rested on a rail to facilitate its movement from plot to plot. The HH was covered with two layers of 6 mil poly and inflated to increase winter insulation and reduce friction and wear of the material against the frame.
Doors on the end of the HH were designed to give an open span of 24 feet with 6.5 feet of vertical clearance to easily overtop any crop and give workers easy access. There were three doors: two doors were 10’ x 6.5’ and the other was 4’ x 6.5’. The two large doors were suspended by pintle-style hinges (two per door) so they could be removed easily and the third door was attached with standard hinges to one of the larger doors. When the HH was to be moved, the doors were removed to allow passage over crops.
The structure was moved in accordance with the farmer's scheduling and concerns for weather challenges. It was discovered that the structure was, at approximately 1800 pounds, a bit too heavy for two people to push with the runner and rail assembly provided. To compensate for added friction, two boat winches with 50 feet each of high-strength nylon webbing were used to pull the HH from one setting to another. This operation was slower than originally anticipated, but it still only took approximately 30 minutes to accomplish.
It was clearly demonstrated, as can be seen in the annual summaries from the cooperating farmer, that the HH performed as expected in preventing frost damage to crops and in elevating the nighttime temperatures for crops in mid- to late-summer when high-desert temperatures become relatively cool in the evening. Protected crops of tomatoes, peppers, and basil were spared, while those exposed to the external environment were stunted or killed by the rather common late freezes. This protection resulted in earlier, and therefore more valuable, produce that reached market.
The same structure had also been used to protect winter greens in an adjacent plot. The companion plot – exposed to the elements – was not planted because there is no record of winter temperatures that would allow growth throughout that season. This use resulted in seasonal production and income that had not previously been possible and the development of new restaurant customers for greens and other crops in the normal growing season. Having produce on a year-round basis gives the producer an advantage in marketing produce in all seasons.
Protecting a spring or just-planted summer crop presents a challenging decision to be made. The decision relates to the relative hardiness of individual crops and the likelihood of damage to that crop. For example, the operator must decide, based on weather reports and local conditions, when to move the HH to protect asparagus, while leaving winter greens with just a row cover. The same decision must be made when it comes to protection of new tomato and other plants as opposed to the asparagus. In many cases, a row cover can be used to offer the required protection for one crop if the other has priority based on its hardiness or value in the market.
We, as planned, planted five plots for the greenhouse to move through, along with control plots outside the structure. The plots were: spring tomatoes, peppers and basil; summer long beans (asparagus beans); fall raspberries; winter greens; and early spring asparagus.
Asparagus and raspberries were not established to the point of needing frost protection, and we elected not to move the greenhouse over them.
Spring tomatoes, basil and peppers showed some improvement in overall yields but showed significant improvement in date of first harvest. We had a difficult spring weather-wise, with several late frosts, the last occurring on June 8 and 9. The field tomatoes were hit hard by the frost and stunted, as were peppers and basil. The greenhouse plants were by then out of the moveable, but had enough growth to withstand some foliage loss. They survived the cold much better than the field controls. Initial harvest from the greenhouse plants was approximately two weeks ahead of the field control plants and were available to market when other similar products were absent.
Long beans grew well over the summer in the heat and humidity of the greenhouse, as opposed to the control plot that survived the late frosts but failed to produce fruit. Clearly, it would take a very unusual summer to produce conditions that would make growing long beans feasible, and the greenhouse made it quite easy.
Winter greens were a surprisingly easy crop to grow, and the quality was exceptional. We lined the north wall of the greenhouse with reflective bubble insulation, but otherwise did nothing to heat the inside of the structure. From an early November planting, we harvested a succession of spinach, lettuce, arugula, broccoli raab, chard and a mix of hardy brassicas from late December through the spring. None of these plants, except spinach, overwinters outside here, and the greens were easy to market when again no comparable produce is available.
Our challenges with the greenhouse were not crop related; they were related to fine-tuning the design and materials. Our end wall materials were too brittle to withstand the winds we get here in the spring, and I repaired many fractured supports. Moving the greenhouse was more difficult than we had envisioned as well, but as we practiced it became easier, and lubricating the rails with a detergent-based lubricant made it relatively easy.
Overall, I was extremely pleased with the greenhouse, even with only three crops to move it across. I am excited to see how it will work with the full complement of five settings.
We maintained five plots for the greenhouse to move through, along with control plots outside the structure. The plots were: spring tomatoes, peppers and basil; summer sweet potatoes; fall raspberries; winter greens; and early spring asparagus.
Asparagus and raspberries were still not established to the point of needing frost protection, and we again elected not to move the greenhouse over them.
Spring tomatoes, basil and peppers showed some improvement in overall yields, and again, significant improvement in date of first harvest. We had an easier spring weather-wise with no late frosts. Still, the two weeks of head start for the greenhouse plants gave them two weeks of earlier harvest, making the produce available for marketing when it is most valued.
Sweet potatoes grew fairly well over the summer in the heat and humidity of the greenhouse but only marginally better than the outside control. More attention to opening and closing the greenhouse at night might help with sweet potato growth, giving them greater night heat, and thereby increasing production. Our harvest was unimpressive, with the outside control about 2/3 that of the inside production. Neither justified the space given to the crop.
Winter greens were again a surprisingly easy crop to grow, and the quality was again exceptional. Again, we lined the north wall of the greenhouse with reflective bubble insulation but otherwise did nothing to heat the inside of the structure. Our winter weather has been significantly less sunny this year than last, with more cold and more persistent cold. From an early-November planting, we are currently harvesting braising mix greens, with significantly more cold damage on the leaves than the previous year, but still enough good quality leaves to make harvesting effective. The least cold-hardy of the crops are suffering this year (especially chard), but not all the greens.
Our challenges with the greenhouse were again related to fine-tuning the design and materials. Our end walls have withstood enough winds to need rebuilding, and we are considering a different design involving less removal of pieces when we move the greenhouse. Moving the greenhouse has became easier; lubricating the rails with a detergent-based lubricant and using boat winches have made it much less stressful. Managing the soil health under the greenhouse has given me pause at times – the intensity of production necessitates greater care in keeping the clay soil from getting compacted and making sure that we work to build the organic matter. Perennial weeds, too, present more of a problem where regular tillage is more difficult. We are working with weed barrier materials to help with this challenge.
Overall, I remain extremely pleased with the greenhouse. I see it adding significantly to my ability to harvest and make available a steady flow of a good variety of produce. I am excited to see how it will work with this year’s full complement of five settings.
Educational & Outreach Activities
Specific items include:
• An interview with an editor was made part of an article in The Grower titled “Tunnel Vision.” The August 2009 issue had the feature theme of: Hooped Structures Pay by Extending the Season.
• A poster and information were presented to Extension and other professionals and producers at the Southwest Marketing Conference in Albuquerque in 2008.
• A poster and information were presented to Extension and other professionals and producers at the Big and Small Extension Conference for northern Colorado in Adams County in 2009.
• A presentation was made to Extension and other professionals and producers at the Small Acreage Symposium in Grand Junction in 2008.
• A presentation was made to Extension Educators at the 2009 Western Region Extension Professional Development Conference in Mesquite, Nevada.
• A presentation is being done for Extension and other professionals and producers for the 2010 Arizona Highlands Garden Conference in Payson, Arizona.
• The Moveable hoophouse (HH) has been featured on at least four tours during 2008 and 2009. One of those tours was the professional development tour for the Colorado County Agents Association held in 2009.
• Numerous articles in regional papers have either featured the HH or mentioned it in the context of season extension for the high-desert of western Colorado.
The primary accomplishments of this project are creating a concept, finding what in that concept worked well, finding its shortcomings and correcting those shortcomings. The corrections will be addressed in the recommendations section.
The Hoophouse (HH) proved to be relatively easy to move and effective in preventing freeze damage as well as increasing the heat units for summer produce and the winter greens that would otherwise be impossible to grow in the high desert climate of western Colorado. The concept of liftable/removable end doors to create a clear span to allow movement over crops also worked well. The roof truss above the door gave enough structural integrity to allow movement of the structure with no additional bracing other than what is called for in the design of the structure.
The primary contribution of this design is that it allows the farmer or gardener to utilize a protective structure that:
• is in different spots at different times of the year,
• the farmer continues to have options to change the
cropping program at any time,
• costs, if used to its full potential, only 20% to 50% of a fixed structure,
• during extreme events, provides the ability to protect valuable perennials at the expence of annuals.
Much was learned in developing the prototype for this moveable hoophouse (HH):
• Size of the structure is at its maximum unless a motorized form of movement is utilized.
• End wall bracing is required to hold the 24’ header steady or it will vibrate back and forth in the wind.
• End wall and doors would be best if they were built from steel, which will hold up under wind loading and vibrations.
• Turnbuckles must have lock nuts to prevent them from loosening with vibrations caused by buffeting winds.
• Smaller HH could be tied down with nylon webbing or braided rope, but all slack must be eliminated by using something like a trucker’s know, shown in the PowerPoint.
• A smaller HH (10’ to 15’ wide) would be an appropriate size for home or hobby gardeners and could be built with a “rail” that consisted of sod (as shown in the Powerpoint). This should be easy for one or two people to move in a few minutes.
• Thought needs to be given by the farmer to the value of the crops and their susceptibility to environmental factors. The choice of which crop to protect, based on potential profit to be gained is not always immediately apparent.
• The HH is best used in combination with floating row covers or some type of low tunnel. This type of system works particularly well with winter greens and can remain to protect the greens when the HH is moved to protect asparagus or start tomatoes or accelerate development of summer raspberries.
• Alignment, in the case study, was set with the HH moving east and west. This positioning allows for the greatest solar radiation during the low-light winter days. This increased collection of solar radiation was enhanced by insulating the north side of the HH with an aluminized insulation that both held in heat and reflected solar radiation back onto the crops. Though we had no way to measure its affects, it is felt that this addition was worthwhile.