However, no-till lettuce is possible today, according to research conducted by Steve Fennimore, University of California Extension weed specialist, Salinas, Calif., and Kai Umeda, University of Arizona area Extension agent, Phoenix.
Unfortunately, there is a brick wall between research and field utilization, and it was built by misinformation about the safety of biotechnology. Growers are reluctant to embrace herbicide-tolerant or other biotechnology enhanced food crops because of the largely unfounded negative perception consumers have about the technology.
Until that can be overcome, growers will not chance introducing into the marketplace lettuce or any other food crop that could create a marketplace backlash.
That will preclude growers from embracing a technology that has proven in research trials to reduce hand-hoeing costs by 90 percent with the application of a quart of Roundup per acre when lettuce was at the two- to six-leaf stage.
Umeda told the 11th annual Desert Vegetable Crop Workshop at Yuma, Ariz., that the variety tested at Salinas and Yuma was glyphosate-tolerant Raider. Research was conducted both on the May-July lettuce deal in Salinas by Fennimore and September-December in Yuma by Umeda.
No crop injury
There was no crop injury at the recommended rate, said Umeda.
For Salinas, Fennimore recorded exceptional weed control at the quart rate at the four- to six-leaf stage. With sequential applications, Umeda said weeds were virtually eliminated compared with not only the non-herbicide check but also the standard Prefar/Kerb preplant herbicide treatment.
For desert lettuce, Umeda said a quart applied over the top at the two- to four-leaf stage was most effective in the desert.
The Roundup-tolerant lettuce plots also produced the highest yield, 65,000 pounds of lettuce per acre compared with a hand-weeded, weed-free plot of 61,000 pounds. Yields were even lower in plots where a preplant herbicide was used along with hand weeding.
The virtually weed free glyphosate-tolerant lettuce plots did not require tillage and that reduced weed control costs by not having repeated flushes of weeds cause by disturbing the soil.
Umeda called the technology "extremely valuable."
Unfortunately, it is at least four to five years away from use by farmers because of consumer reluctance to embrace genetically modified vegetable crops.