Growing crops in Southwest Utah’s desert is made even more difficult by erratic and extreme weather. The spring can have highs in the 80s and lows close to freezing, or a freak cold snap may hit in late May after a month of warm weather. This project sought to find cost effective ways to moderate these temperature extremes to extend the growing season.
The season-extension experiment involved testing paper and plastic mulch by punching holes in the material to transplant warm-season crops – tomatoes and summer squash grown from seed in the greenhouse – and by covering cool-season crops with the material.
In the experiment with the cool-season crops, harvest was a week to 10 days earlier than normal with the covers, achieving the project’s goals. However, as the season progressed, and July temperatures rose to between 105 and 115 degrees, the cool-season crops bolted and their harvest ended.
The warm-season crop experiment had mixed results. The tomatoes recovered from early damage caused by wind-whipped fabric row covers but ultimately succumbed to curly top virus. Meanwhile, the covers helped stimulate growth of melons and eggplant, but the melons also died before fruiting, probably because of the cucumber mosaic virus. The eggplant under the mulch began producing two weeks earlier than the exposed eggplant, thriving to maturity and providing the farm with an excellent crop.
· Attempt to extend the growing season in the desert Southwest using row covers as a means of moderating temperature fluctuations in the spring, moderating the extreme of summer heat and extending the growing season into the fall
· Test the covers’ efficacy on two groups of crops: cool-season and warm-season
· Maintain detailed notes on daily high and low temperatures, seeding dates, germination dates, transplanting dates, irrigation and weeding schedules, harvest dates and yields
· Disseminate information to other producers through a field day
On the experiment site, producer Aviva Maller, grows cool-season crops that include lettuce, salad mix, arugula, rappinni, bok choy, broccoli, carrots, beets, spinach and radish. Row covers were placed on the crops after planting in late winter, with row ends left open as controls. The row covers promoted quicker growth, especially with greens and lettuces, and most covered crops were harvested a week to 10 days earlier than the uncovered crops.
One concern, however, was that weeds flourished unseen under the covers. Two rolls of agro-fabric, a transparent row cover, were then laid over the crops, which allowed observation of both crop and weed growth. While the agro-fabric is five times more expensive than the plastic row cover, it is supposed to last five times as long. Maller observed that is a superior product for extending the growing season.
The row cover and agro-fabric were also tested for extending the salad mix harvest into the summer, but excessive temperatures, ranging from 105 to 115, caused the lettuces and greens to bolt, suggesting that no cover crop could help plants during such extreme heat.
The row covers appeared to help germination and growth of fall-planted greens and lettuces, with crops under the agro-fabric growing faster than those uncovered.
Extending the season for tomatoes, the main summer cash crop, was the primary goal. The tomatoes were planted in the middle two weeks of May into red plastic mulch, advertised to deter weeds and increase growth by 20%, then covered with row covers. However, seasonal winds whipped the plastic cover, damaging the tomatoes. The covers were removed and the tomatoes recovered in a couple of weeks. Planting into the plastic mulch took about eight times as long as normal (4 hours versus a half hour to plant 100 tomatoes. Another challenge was determining where to plant the tomatoes so they would be close to the drip emitters, a necessity in the sandy soil.
Yields were higher in the mulched beds compared with the controls, but the farm was infested with leafhoppers that spread curly top virus, and 85% of the tomatoes died. On the plus side, the mulch did reduce weeding chores.
Melons and eggplant were also planted into the plastic mulch. The mulched melons grew about twice as fast as those not mulched, but they all died before ripening, probable victims of cucumber mosaic virus.
The mulched eggplant began producing two weeks ahead of the control, although the yields remained about the same for each. Still, thanks to improved soil moisture and structure under the mulch, reduced weeding time and quicker growth, the eggplant results were considered very successful.
BENEFITS OR IMPACT ON AGRICULTURE
The cost of the product and the initial labor of laying plastic mulch appeared to be worthwhile for a small operation. The plastic mulch also reduced weeding, a major job on Maller’s farm.
“Using plastic mulches helped reduce the time of weeding on the mulched beds, proving to be an economical system I will work into my farm in future seasons,” she said.
In addition, the row covers hasten crop growth, especially cool-season greens and lettuces.
REACTIONS FROM PRODUCERS
In wind storms, the row covers can damage large transplants, a problem that may be overcome with protective structures.
Also, the agro-fabric, because of its transparency, was the easiest row cover to use. It costs more but is supposed to last longer. Maller is continuing its use on her farm to assess its economic viability.
The agricultural professional, Rich Heflebower, made a presentation on “Fall Gardening” in St. George in which he used slides of the various season-extending techniques tested in the project.