- Author: Amber Vinchesi-Vahl
- Posted by: Gale Perez
Conventional processing tomato weed management in California often includes pre-plant herbicides (trifluralin and/or s-metolachlor), followed by cultivation, and hand hoeing. Rimsulfuron herbicide can also be used in conventional systems and can be applied either pre or post transplanting. Post-transplant applications of rimsulfuron can selectively remove nightshades if applied when the weeds are very young, no more than 2 true leaves, however, long plant-back restrictions may limit its use. Therefore, the use of hand crews is often needed to remove weeds that emerge in the plant row, where standard cultivation equipment is ineffective.
While both robotic cultivators and finger weeders have been used and evaluated in many vegetable crops, there has been little research evaluating these tools in processing tomatoes and how well they may complement or replace a traditional herbicide program. The main objective of this project was to evaluate crop safety, weed control, time, and costs associated with using mechanical cultivators as part of a conventional weed management program in processing tomatoes. This work is supported by the California Tomato Research Institute, with assistance from grower cooperators.
Methods
This project was conducted in 2020 and 2021 in both Colusa and Merced counties.UCCE Vegetable Crops Advisor, Scott Stoddard, led project efforts in Merced County. Only the Colusa site data will be presented here. The Colusa County field site was located just north of Colusa, CA and the same site was used both years. The field was transplanted to double row tomatoes, on 60” beds. Plot size was 5 beds by 250 ft length, except for Control (Treatment 4) which was 5 beds by 100 ft length to minimize impact. Each treatment was replicated three times. The following treatments were evaluated:
- Rimsulfuron at 2oz/A (grower standard)
- Automated cultivator (1 bed/pass)
- Finger weeder mechanical cultivator (5 beds/pass)
- Control: no in-row cultivation, no post-transplant herbicide.
Results
Weed control results are shown in Figure 5. In 2020, the Robovator and finger weeder did an excellent job of weed control on all plots. In 2020, the Robovator worked very well, providing up to 85% control on average two weeks and four weeks after it was run, and we saw very little crop injury (Figure 6). However in 2021, due to heavy winds in early May, the young tomato plants were not upright, and the robotic weeder had difficulty distinguishing where the stem of the plant was compared to the top of the plant. These plots suffered 11-19% crop loss, which also occurred at the Merced site in 2020 (Figure 7). Despite the crop injury, average weed control was 71% after 2 weeks in 2021 and there was no negative impact on yield. The finger weeder provided 66% on average two weeks post-treatment in 2020. It is worth noting that by plot, the finger weeder provided over 90% control post-treatment in two of the plots. The third plot showed poor control due to heavy bindweed pressure, therefore bringing the average down. The finger weeder also provided excellent control at the Merced site in 2020. In 2021, the finger weeder provided an average of 56% control two weeks after treatment and 66% control four weeks after treatment. The grower standard herbicide treatment of rimsulfuron provided 34% and 44% control on average at two and four weeks after application in 2021, but it is worth noting this field did not have heavy nightshade pressure. Despite the numeric differences between treatments shown in Figure 5, there was no significant difference between the cultivator treatments and the grower standard (rimsulfuron) for weed control in either year, due to high variation in weed pressure between plots, which can be seen from the high standard error values.
In general, hand weeding provided 60-100% control between 2020 and 2021. Hand weeding times and costs were not significantly different between the grower standard (rimsulfuron), finger weeder or robotic weeder treatments in both years and all treatments significantly decreased time and costs compared to the control plots (Table 1). Weed pressure increased in 2021 leading to higher weed counts and longer hand weeding times and associated costs compared to 2020. There were no significant differences in yield between plots in 2020 or 2021.
Summary
Field variation and weed species influenced weed pressure and control, some plots had >300 weeds and others only had 10. There was poor bindweed control from cultivators and hand-weeding crews, which was expected based on the biology of bindweed. Both in-row cultivators provided decent control in 2020. The finger weeder was able to cover five beds per pass and moved quickly through the field compared to the Robovator. All treatments significantly reduced hand weeding costs and time compared to the control in 2020. Despite the crop injury issues with the automated cultivator in 2021, the Robovator plots resulted in the highest % weed control and fastest hand-weeding times.
The finger weeder is gaining popularity in the Sacramento Valley and provides an option for in-row mechanical cultivation without the expense of an automated weeder. Timing is key when using either type of in-row cultivator. The size of the tomato plant and the size of emerging weeds needs to be just right to avoid crop injury while also removing young weeds. The finger weeder provided excellent weed control in Colusa and Merced in 2020, despite poor bindweed control. The automated weeder provided excellent weed control at the Colusa site, but with high crop injury and technological challenges. When working correctly, automated weeders provide accurate and precise weed control, though issues can arise when conditions are not as favorable. In-row mechanical cultivators, like the finger weeder, are more economical, but automated weeders are becoming more prevalent in California for vegetable production systems.
Many thanks to the California Tomato Research Institute, Steve Fennimore, Scott Stoddard, and our grower cooperators for working with us on this project.
Amber Vinchesi-Vahl is the UC Cooperative Extension Vegetable Crops Advisor for Colusa, Sutter and Yuba counties.
This article was published in the March/April 2022 issue of Progressive Crop Consultant.
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- Author: Richard Smith
- Posted by: Gale Perez
There is a great deal of interest in developing automated weeders for use in vegetable crops. Innovations that are being developed include: 1) the use of deep learning to train computers to better distinguish crop plants from weeds; 2) use of spray kill mechanism that can allow for pin point application of herbicides (e.g. Seek & Spray, Blue River Technologies); and 3) autonomous weeders (e.g. Naio, France; AgBot, Australia; Anatis, France; FarmWise, San Francisco, CA). A quick search on YouTube will reveal a large number of autoweeding concepts that are being developed in many parts of the world. One interesting concept is a solar powered autonomous weeder, EcoRobotix (Switzerland), that removes weeds from the seedline by applying a micro-dose of herbicide.
At present, the automated weeders are quite expensive and are only affordable by larger operations. However, one company is offering monthly rentals of their machine, which allows growers to try out the technology before making a large investment, as well as making the technology accessible to smaller growers. Considering we are still in the early stages of the development of this technology, it will be fascinating to watch its adoption and progress as time moves forward.
- Re-posted by: Gale Perez
From the UC Davis News Service • January 21, 2015
Led by Professor David Slaughter of the UC Davis Department of Biological and Agricultural Engineering, the project recently received a $2.7 million grant from the U.S. Department of Agriculture Specialty Crop Research Initiative. It addresses a problem that has vexed precision weed management for years: How do you devise a robotic cultivator that can quickly distinguish friend from foe?
“Machines can recognize a weed, and they can recognize a crop plant, but they have trouble distinguishing one pattern from another when they are co-mingled, as is often the case with weeds and young crops in the field, particularly when traveling at a typical tractor speed of three-feet-per-second or more,” Slaughter said.
Slaughter's team is designing a robotic cultivator that can remove weeds in commercial fields as carefully as gardeners pull weeds in their own backyard, without the time-consuming labor and cost. They're developing a “smart” cultivator with small knives that reach out to uproot weeds and retract to keep crops intact.
It will weed the beds of any row crop and will be especially useful in wide beds of densely seeded crops like spinach and baby lettuce, which can turn green almost overnight with weeds and leafy crops.
“Current vision-sensing mechanical cultivators can sometimes recognize weeds along the edges of wide beds, or seed lines, as we call them, but they get lost in the middle,” said Steve Fennimore, Cooperative Extension weed specialist with the UC Davis Department of Plant Sciences, a member of the new robotic cultivator team. “Workers often have to go back through and hand-weed them.”
How will the new cultivator distinguish friend from foe? Thanks to a safe, simple seed coating, the plants will signal the cultivator by emitting a faint, fluorescent glow that will appear when seedlings emerge and are most vulnerable, then vanish as plants grow and can out-compete weeds for sun, water and nutrients.
“It won't involve biotechnology or any genetic engineering,” Slaughter said. “The seeds will be coated with a safe, inert, fluorescent material.”
Seeds are commonly coated with various materials (like fertilizers, fungicides or herbicides) for different reasons. Some seeds are coated to protect them from birds, rodents and stress. Some seeds are coated with colorful, inert material to make them easier to plant and easier to pick up if they spill. Some seeds are coated as a way for companies to protect their brand identity — a process they call “track and trace.”
To develop the seed coating, Slaughter's team will work with researchers from the Seed Biotechnology Center at UC Davis and Aginnovation, a company that specializes in seed technology, located in Walnut Grove in Sacramento County. Aginnovation is a founding member of the Centor Group, a group of independent companies from around the world that work together to deliver leading-edge technology and services to the agricultural seed industry.
This new smart-cultivator technology could be the breakthrough needed to help crop plants communicate with existing machines like automated lettuce thinners, machines that drive through heavily seeded fields and remove all but the most viable plants.
The new cultivator should move more quickly through a field than current vision-sensor models because it won't take as long for the machine to distinguish the good guys from the bad guys. That's good news for vegetable growers like Alain Pincot, managing partner of Bonipak Farms in Santa Maria.
“As the cost of labor rises in California, mechanical cultivators become more important to both organic and conventional ag production,” Pincot said. “We've been fairly happy with our existing automatic weeders, but we would be interested in a new type of cultivator if it moved more quickly and could accommodate beds of various widths. A robotic weeder with a higher speed and good accuracy along the row would be a winning machine.”
That's no doubt why the USDA is investing $2.7 million in the new cultivator design, which will take shape over the next five years.
Several researchers from various disciplines in different states are teaming up on the project. In addition to Slaughter and Fennimore, they include Professors Ken Giles, Shrinivasa Upadhyaya and Stavros Vougioukas, all with the UC Davis Department of Biological and Agricultural Engineering; Richard Smith, Cooperative Extension farm advisor in Salinas County, who specializes in vegetable crop production and weed science; Laura Tourte, Cooperative Extension farm advisor in Santa Cruz, Monterey and San Benito counties, specializing in farm management; Mark Siemens, professor and Cooperative Extension specialist with the University of Arizona Department of Agricultural and Biosystems Engineering; Professor Manoj Karkee with the Washington State University Biological Systems Engineering Department; and Professor Qin Zhang, director of the Center for Precision and Automated Agricultural Systems at Washington State University.
- David Slaughter, Biological and Agricultural Engineering, (530) 752-5553, dcslaughter@ucdavis.edu
- Steve Fennimore, Plant Sciences, (831) 755-2896, safennimore@ucdavis.edu