A detection by the camera triggers an arm that pushes the crop leaves out of reach of the harvester’s blades, keeping the contaminant from being harvested and fed into the processing line. The growers who partnered with Harvest Moon on the project funded the prototypes and testing, and now will be the first to use it.While John Deere isn’t building automated weeders for vegetable crops, it is interested in the technology involved. In 2017, Deere paid $305 million to acquire Sunnyvale startup Blue River Technology, which had developed plant-recognition technology that was incorporated in a lettuce-thinning machine used by growers in the Salinas Valley. Since then, however, Deere has focused Blue River’s technology on cotton, and, according to UC and University of Arizona extension researchers, the company no longer offers lettuce thinning services in the Salinas Valley or Yuma, Arizona . A major motivation for the focus on cotton, and potentially other commodity crops, is the declining effectiveness of widely used broadcast herbicides like Roundup that are applied to fields of crops genetically modified to tolerate the herbicide . Chemical companies are struggling to develop next-generation chemicals that are effective and satisfy environmental regulators. Weed-recognition technology could lead to a new approach to weed control — replacing broadcast herbicides with higher-potency, focused, grow trays small doses aimed directly at weeds, or, for some applications, robotic hoes — that promises less overall use of herbicide and more effective weed control.
Blue River says a viable version of its technology for cotton is still several years from commercial release . In vegetable crops, as with commodity crops, existing herbicides are becoming less effective, said Steve Fennimore, a UCCE weed specialist based in Salinas. But the prospects for new herbicides suitable for vegetable crops are even dimmer than those for commodity crops because vegetable crops represent a relatively small market for chemical makers. “The chemical industry invests very little — essentially nothing — on these crops,” Fennimore said. Due to the complexity of chemical development and the high cost of the regulatory approval process, large chemical companies are effectively the only entities capable of commercializing a new herbicide, for any crop. But for automated weeding, Fennimore noted, there are essentially no regulatory hurdles, and it doesn’t take the resources of a giant company to develop working prototypes. Small firms can innovate meaningfully. As a result, Fennimore said, the best prospects for advances in vegetable weed control are likely to be through improved machines, developed by small firms and growers, with support from UC and the research community.Currently, automated weeding systems work well in relatively simple settings — low weed density, little or no overlap of weeds and crop plants. In more complex settings, current image-recognition technology struggles to reliably identify which plants should be removed. David Slaughter, UC Davis professor of biological and agricultural engineering, is working with nine collaborators — from UC Davis, UCCE, Washington State University and the University of Arizona — on a $2.7 million USDA-funded project to improve mechanized weed control by developing better systems for what’s called crop signaling — distinguishing crop plants from weeds.
One approach uses a biodegradable straw with a fluorescent coating inserted into the soil with the crop plant. The coating is readily detected by a camera, which can then tell the weeding equipment which spots to avoid. Another crop-signaling method uses high-precision GPS to record planting locations. “We can make a map of every seedling,” said Slaughter. When it’s time for weeding, all plants that aren’t on the map are removed. Slaughter noted that another general path of evolution for automation is the adaptation of growing practices — plant spacing, crop varieties, the timing of weeding and so on — to suit the available technologies.Harvest is generally the most costly step in vegetable production, due chiefly to the amount of labor required. Salinas-based Taylor Farms, the world’s largest salad producer, has invested heavily in harvest automation, developing romaine lettuce and cabbage harvesting equipment used by the growers it contracts with to supply the bagged salad market . But for many vegetable crops, as well as other major Central Coast crops like strawberries, effective automated harvesters have yet to be proven. “Automating the harvest — that’s the Holy Grail for pretty much everybody,” said Brian Antle, who runs the planting automation company PlantTape and is a member of the family that co-owns Tanimura & Antle, one of the largest fresh produce growers in the Salinas Valley. An intermediate step is “co-robotics” — designing robots to work alongside human laborers, with the robots handling simple tasks while people continue to perform the more complex and delicate actions.
One example is self-guided carts that assist human strawberry pickers by carrying full trays of strawberries out of the field and returning with empty trays. “The recognition is that the agricultural environment is very complex, and we may not see full autonomy in the next decade,” said Slaughter.In the 1960s, the release of a processing tomato harvester, developed by two UC Davis researchers, transformed the production of that crop. Only larger growers could afford one, and because the machine dramatically reduced the costs of harvesting, it created a powerful economy of scale that encouraged big growers to expand. In the first few years after the harvester’s introduction, a large fraction of the state’s tomato growers left the business. Advocates for small farmers and farm workers organized to criticize UC’s role in developing the harvester and to push for more UC support for small farmers. In a 1979 lawsuit, they argued that the tomato harvester favored large farmers, violating the public benefit mission of land-grant university research as established by the Hatch Act of 1887. UC prevailed in court after a 10-year legal battle. But the conflict drove lasting changes at UC and elsewhere. Federal funding for automation research declined, and agricultural engineering departments shifted focus to other types of research, Slaughter said. Today, UC ANR programs targeting small farms include the Sustainable Agriculture Research and Extension Program and the UC ANR Small Farm Working Group. Like previous waves of mechanization, automation in vegetable crops stands to mainly benefit larger farms, at least initially. Large, highly standardized fields of a single crop tend to be better suited to mechanization than the fields of a small farm growing a variety of crops. And, as noted earlier, large growers are currently the main market for — and often the lead investors in — novel automation technologies, which tend to be designed to solve the problems they face on their own farms. Margaret Lloyd, a UCCE small farms advisor in Yolo County, said that automation technologies can benefit small farms too — but small growers need versions of the machines that are less expensive, more versatile, and designed with small scale in mind. “Could you make a machine that does four rows at a time, but also make one that is simpler and cheaper and only does one row?” she said. Yes, probably, said UCCE’s Fennimore — once the technology is well developed. “Do tractors only benefit large growers? No, because we now know how to build tractors and there are lots of them, new and used, and thousands of grower customers are each paying a small fraction of the research and development cost to improve tractors,” he said. “Eventually this will be true for weeders and other smart technology.”Increased rotational production of many agronomic grass and cereal grain crops seems destined to be part of the agricultural future. This may occur, not only to produce more food for ever-increasing numbers of people and livestock on the planet, but also to provide feedstocks for lignocellulosic biofuels made from plant residues, such as from straw remaining after harvest . These crops may include the small grain staples widely grown for human consumption, e.g., wheat, rice, barley, etc., grow systems for weed as well as those grown primarily for vegetative biomass and livestock feed, such as sugarcane, sudangrass and sorghum. Increased sequencing into grass family crops may occur even in agricultural regions, such as in the Mediterranean climatic zones, where intensive relay planting of high-value horticultural crops is commonly practiced. Due to rising costs, increased scarcity of water and other resources, and the vital importance of maintaining long-term, sustainable agricultural production systems, improving cropping efficiency through value-added, or “multi-tasking” uses for all portions of crops is becoming increasingly necessary . At the same time, care must be taken so as to not remove excessive amounts of plant biomass from the land, so that soil quality and fertility suffer.
The development of pest management tactics based on use of non-harvested crop components can be an important facet of overall agricultural sustainability. It is widely known, but often not considered, that many poaceous plants possess properties that are inhibitory to other life forms . The bioactivity of poaceous plants may be based on allelopathy and/or toxicity of their decomposition products in soil . Allelopathy depends, to a great extent, on organisms producing secondary metabolites — chemical compounds not necessarily needed for their basic metabolism, but which often confer ecological advantages by killing, weakening or repelling nearby competitors for nutrients, space or other niche resources . For example, many of the synthesized antibiotics used in human and animal medicine were originally discovered as secondary metabolites of various microorganisms. Although potentially useful levels of pesticidal activity have been demonstrated from certain poaceous plants and from their decomposing residues, the broad range of these toxic properties also has resulted in undesirable instances of phytotoxicity to subsequent crops . The potential of biomass crops, primarily those in the cabbage family , for use in soil biofumigation and soil/water bioremediation was recently discussed . In previous experimentation with residues of brassicaceous and alliaceous crop plants as soil amendments, biocidal activity was shown to increase with increasing soil temperature. We also reported that cover cropping with a sorghum– sudangrass hybrid [Sorghum bicolor Moench x Sorghum sudanense Stapf. = “sudex”] was detrimental to subsequent tomato, lettuce and broccoli transplants because of allelopathic phytotoxicity . Indeed, various Sorghum spp., such as sudex, grain sorghum, sudangrass and johnsongrass , have been shown to inhibit emergence or development of a broad range of annual and perennial crop species . However, in addition to their sometimes negative impact on subsequently planted crops, the contributions of various poaceous species and cultivars on populations of weeds also must be considered . For example, significant reductions in weed populations have been reported in wheat following sorghum , and root exudates of S. bicolor reduced growth of velvet leaf, thorn apple , redroot pigweed , crabgrass , yellow foxtail and barnyardgrass . These findings point to possible pest management utility of crop rotations with agronomic grasses. In this study, our objectives were to conduct experiments with containerized soil, at laboratory scale, to test the pest management effects of amendment with residues of small grain crops. The experiments, conducted at two temperature regimens, evaluated survival and activity of the nematode plant pathogen Meloidogyne incognita, and the fungal pathogens Sclerotium rolfsii and Pythium ultimum, following exposure to cultivated wheat, barley, oat and triticale residues in soil. Furthermore, we conducted field experiments to test effects of sudex cover crop plants, previously shown to be deleterious to vegetable crop transplants , for weed control.As described in a preliminary report , Hanford fine sandy loam soil naturally infested with M. incognita [ca 150 second-stage juveniles per liter of soil] and P. ultimum [ca 29 propagules per gram of soil] was used. Laboratory-grown sclerotia of S. rolfsii were added to the soils in mesh bags prior to treatment. Soil for treatment was loaded into bioreactors, consisting of wide-mouthed, 2-liter-capacity glass jars, with openings covered by clear, 0.031 mm , low-density polyethylene film, tightly secured with rubber bands. This technique allowed for limited gas exchange between bioreactors and ambient air, and simulated conditions in field soil during solarization or bed mulching. Four replicate bioreactors were then incubated in a modified Wisconsin-type water bath with diurnal temperature maximum and minimum of 38°C and 27°C, respectively, while four others were simultaneously maintained in a similar water bath set at a constant 23°C . The elevated temperature water bath was set to deliver 8 h heating per day, which gave samples in bioreactors ca 6 h at maximum temperature during each 24-h period.