Good plant health is dependent on a strong and healthy root system. Similarly, a healthy plant is dependent on a healthy soil. A soil with good aggregation and physical structure is conducive to better water-holding capacity and root penetration and development. Soil health, strong root system development, and plant health are three inter-related and fundamental components of vigorous and healthy crop plants.
Root systems provide the foundation for plant development. Roots are responsible for all water and nutrient uptake by the plant, and they provide the physical anchoring and support of the plant structure.
Each plant and crop species has its own “personality” and growth habits, that includes root systems. Accordingly, root systems have unique characteristics among plants species (Gardner, Pearce, and Mitchel, 1985; Moore et al., 1998).
Young plant roots, particularly at the time of germination and stand establishment, are generally the most sensitive plant part to soil and water salinity. In fact, seedling plant sensitivity to salinity can often be measured by approximately ½ of the tabulated salinity tolerance guidelines.
In general plant root systems constitute 30-50% of the total plant dry matter. When post-harvest plant residues are incorporated into the soil, the root systems provide a significant contribution to that plant material and final carbon (C) contributions to the soil, which is an important factor contributing to soil health.
The first thing a seed develops in the germination process is a primary root that grows downward into the soil. We often refer to this as the “stinger” root that extends from a germinating seed. New cells are formed at the tip of the primary root as it extends downward into the soil forming a “thimble-shaped” cluster of cells called a root cap (Figure 1).
The root cap serves as a type of shield that helps the root penetrate the soil and it protects the developing root tissue. As the root grows downward into the soil the root cap cells are sloughed off creating a slimy surface that helps lubricate the root as it extends deeper into the soil (Moore et al., 1998).
The growing point (apical meristem) for the developing root is just behind the root cap. This growing point is the zone of new cell formation that facilitates root growth and replaces the cells that are sloughed off as the root grows through the soil. The new cells elongate and serve to extend the roots further into the soil (Figure 1).
The most active parts of the plant root system for mineral nutrient and water uptake are in the tiny root hairs that are formed in zone behind the apical meristem. Root hairs are only formed in the relatively new and freshly developed root tissue (Moore et al., 1998). The root hairs are extremely small, tender, and physiologically active. Healthy fresh young roots and root hairs should be clean and white.
Root hairs are often referred to as “feeder roots” due to their high-level of activity in securing water and nutrients from the soil for the growing plant. In the process of transplanting, it is important to protect the feeder roots as much as possible and promote their health to ensure rapid adaptation to the new soil environment.
Young plants have the capacity to develop basic aboveground tissue to perform sufficient photosynthesis for establishment and growth. Above ground growth is dependent on the plant’s ability to take up mineral nutrients and water from the soil from the root system. Sometimes it can appear that plants are not growing rapidly while the young crop is investing energy and resources into root system development.
Energy for root development is dependent upon the photosynthetic capacity of the plant. This demonstrates the synchrony required between plant shoots and roots and this is the foundation for complete and subsequent plant growth and development.
The depth of the roots will vary according to the soil physical conditions and effective soil depth, soil fertility and salinity management, plant-available water, and of course the natural rooting characteristics of the plant.
In general, there are two basic types of plant root systems. Broadleaf plants (dicotyledonous) and coniferous plants (gymnosperms) commonly have a taproot system the extends downward through the soil developing root branches from the primary root stem (Figure 2).
Grass plants and their relatives (monocotyledonous plants) produce fibrous root systems that branch extensively and radiate out into the soil from the plant base (Figures 2 and 3).
In general, taproots tend to be deeper with extensive branching from the primary root, develop woody tissue on older roots, and are generally long-lived. In contrast, fibrous roots tend to be smaller, short-lived, with less branching (Moore et al., 1998).
As roots age, they become more fully developed in conducting nutrients and water to the growing points of the plant, both above and belowground. In all cases, the young and freshly developed root hairs (feeder roots) are the primary zone of water and mineral nutrient uptake.
As root systems age, the older roots will die, and new root tissue is formed. As dead roots are sloughed off, the discarded tissue is attacked by naturally occurring, beneficial soil organisms (bacteria, fungi, protozoa, and worms) the release of mineral nutrients and produce soil organic matter. Turnover of root tissue is an important aspect of plant contributions to soil carbon (C), organic matter, and general soil health.
We do not directly see the plant root systems, and we cannot watch root hair development. But it is good to be conscious of root system development since all mineral nutrients, water uptake, and structural support are provided through the roots.
In field evaluations it is necessary to sacrifice a few plants occasionally and evaluate root system health and development. Healthy plant roots should have white and clear tissues on their surface. Examples are shown in Figures 3 and 4.
Accordingly, it is good to review and understand normal root structure and function as we work to manage crop plants for optimum growth, development, and yield.
Figure 1. Basic root tip anatomy.
Figure 2. Examples of taproot and fibrous root systems.
Figure 3. Healthy fibrous root systems on a cereal
grain crop. Source: Grain Central, 2021.
Figure 4. Clean and healthy lettuce plant roots.
Source: Fifth Season Gardening.
References:
Gardner, Pearce, and Mitchell. 1985. Physiology of Crop Plants. The Iowa State University Press.
Moore R., W.D. Clark, and D.S. Vodopich. Botany. The McGraw-Hill Companies. 1998. ISBN: 0-697-38363-1
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I am seeking samples of downy mildew on lettuce from around Yuma County to support the Michelmore Lab and their ongoing efforts to help characterize the downy mildew populations of the United States. The Michelmore Lab has led the charge on a survey of Bremia variants since 1980 and has been instrumental in demystifying the gene-for-gene nature of lettuce resistance to downy mildew.
Their group invites growers across the United States to submit downy mildew infected plant samples, which are then used to culture the Bremia on live host plants. The team then inoculates a panel of lettuce varieties carrying known resistance genes to determine the race of each isolate they receive. Identifying which races occur in which specific fields is essential to guiding the breeding of new resistant cultivars and maximizing the effectiveness of host-based genetic disease management. The data obtained from these tests are also used to designate new Bremia races through the International Bremia Evaluation Board.
Your contribution will help breed better lettuce for Yuma. This means less breakdown of resistance in the field, and better yields for Yuma growers. To facilitate these submissions the Yuma Plant Health Clinic will be setting up a separate drop-off point and submission sheet for downy mildew sample submissions in the same hallway we use for standard plant diagnostic submissions. The drop-off point will be clearly labelled and consist of a chest-style refrigerator and printed copies of the submission form. It is vital to keep these samples cool so they remain viable for future inoculations, so please place your samples inside of the refrigerator before you leave.
Shipping will be handled by the clinic. All we ask is that you fill out the submission form as completely as you can. An example of the questions that are asked in that form so you can prepare ahead of time can be found HERE .This week, we initiated a trial investigating the effectiveness of applying fungicides post-emergence with an alternative tool, a point injection applicator, to control the pathogen which causes Fusarium wilt of lettuce. The hypothesis is to inject fungicide where it is needed to protect plants from the soilborne disease – in the root zone, without injuring crop roots. We are doing this with a point injection applicator, a device designed to apply ag chemicals post emergence with minimal root damage and soil disturbance. The applicator utilizes hollow pointed tips attached to a rotatable wheel to inject liquid products into the root zone at precise intervals and depths (Fig. 1). The advantage of point injection compared to conventional shank injection is that root pruning is minimized, reducing the number of wounds that provide a pathway for the pathogen to infect the plant. Stay tuned for trial details and results.
Fig. 1. Point injection applicator operating in iceberg lettuce.
Fig. 2. Click here or the image above to see the point injection system in action.
If you've been wondering whether all this talk about robotic weeders is just hype or if these machines can actually handle the real challenges we face in our desert fields, you're not alone. Many growers are asking the same question, and fortunately, we now have solid field data from right here in the Southwest to give you a straight answer.
The bottom line? Yes, these machines work—but they're not magic bullets. They need to be part of your overall weed management strategy, not a replacement for everything else you're doing.
What We're Actually Seeing in Local Fields
Over the past few years, researchers and growers in Yuma and the Imperial Valley have been putting various robotic weeding systems through their paces in lettuce, leafy greens, and other vegetable crops. The results have been pretty encouraging, though there are definitely some caveats (Smith et al., 2021; UC ANR, 2025).
These machines use cameras and artificial intelligence to distinguish crops from weeds, then either physically remove the weeds with mechanical tools or zap them with lasers. Depending on how heavy your weed pressure is and which system you're using, they can knock out anywhere from 30% to as much as 98% of your weeds (UC ANR, 2025; NIFA, 2025). That's a pretty wide range, but even at the lower end, you're talking about significant labor savings.
Here's a number that'll get your attention: trials at the UA Yuma Ag Center found that hand weeding crews were spending about 2.8 hours per acre on average. When robotic weeders were brought in first, follow-up hand weeding dropped to as little as 0.4 hours per acre in fields with moderate weed pressure (NIFA, 2025; NC State Extension, 2025). That's not just helpful—that's a potential game-changer when you can't find enough crew members during peak season.
The Good, The Bad, and The Reality Check
Let's talk about what these machines do well and where they still need work.
Where they shine:
Labor has been our biggest headache for years now, and this is where robotic weeders really prove their worth. They don't call in sick, they can work around the clock if needed, and they significantly cut down the hours your hand crews need to spend in the field (NIFA, 2025; Farmonaut, 2025; AZCentral, 2025). For many operations, that alone justifies looking into the technology.
The good news for your bottom line is that properly configured robotic weeders don't hurt your crop. Multiple studies have confirmed that lettuce stands, head size, and overall yields hold up just fine when these machines do their thing (Smith et al., 2021; UC ANR, 2025). You're not trading weed control for crop damage.
If you're farming organically or trying to cut back on herbicide use, these systems offer a way to stay on top of weeds without spraying (Carbon Robotics, 2022; Farmonaut, 2025; CORDIS, 2024). That's becoming more important as herbicide resistance continues to spread, and consumers keep pushing for reduced chemical inputs.
Where they struggle:
Here's the reality—robotic weeders aren't perfect, and anyone who tells you they'll eliminate all your hand weeding is selling you something. The biggest issue we're seeing is with "doubles"—those places where you've got two plants too close together or weeds right up against a crop plant. Most systems just can't handle those situations reliably yet (Smith et al., 2021; UC ANR, 2025; Growing Produce, 2023). You'll still need hand crews for cleanup work.
The price tag is another issue, especially for smaller operations. These aren't cheap machines, though costs are starting to come down, and some companies are offering custom services where they bring the equipment to your farm rather than you buying it outright (Smith et al., 2021; Farmonaut, 2025; Anthropocene Magazine, 2024).
And let's be honest about our Southwest conditions—rocky ground, uneven terrain, and our infamous dust storms can all throw a wrench in the works. The technology is getting better at handling these challenges, but it's something to keep in mind (HowToRobot, 2023).
Does It Make Financial Sense?
Recent economic analyses, including a case study from Western Growers, show that integrating robotic weeders can reduce your overall weeding costs while cutting herbicide expenses (UA ACIS, 2025; Anthropocene Magazine, 2024). The research suggests that getting in early—before herbicide resistance becomes a crisis in your operation—gives you the best return on investment.
Think of it this way: you're not just buying a piece of equipment, you're investing in keeping your weed management options open for the future.
Making It Work for Your Operation
If you're considering robotic weeders, here's what seems to work best based on what we're seeing in the field:
Don't try to replace your hand crews entirely. Use the robots for the bulk of the work, then have your crews come through and get the misses and the doubles. That combination gives you the cleanest fields with the least labor (UC ANR, 2025; NC State Extension, 2025).
Run the numbers carefully for your specific situation. How much are you spending on hand labor now? How hard is it to find crews when you need them? What are your weed pressure levels like? The answers to these questions will tell you whether the investment makes sense (Smith et al., 2021; Anthropocene Magazine, 2024).
Look into custom services or equipment-sharing arrangements if buying your own machine seems like too big a leap. The technology is evolving fast enough that you might not want to own it outright anyway.
See for Yourself
We're going to have several different robotic weeding and thinning machines running live demonstrations at our AgTech Field Day on November 13-14, 2025, at the UA Yuma Agricultural Center (6425 W. 8th Street). This is your chance to see these machines working large-scale in real desert conditions and ask the manufacturers all your tough questions (Desert Ag Solutions, 2024; Western Growers, 2024; Desert Ag Solutions FarmTech, 2024).
We'll kick things off on November 13 at 7:00 AM with field demonstrations running until noon. You'll see robotic weeders, automated thinners, and precision sprayers all operating in actual field conditions—not some perfect demo plot. After lunch, you'll have time to talk with the equipment reps and other growers about their experiences. On November 14, we've got expert panels discussing where this technology is headed and what it means for desert agriculture (Desert Ag Solutions FarmTech, 2024).
Bring your questions, bring your skepticism, and come see for yourself whether this technology has a place in your operation.
Where Do We Go From Here?
Look, robotic weeders aren't going to solve every weed problem we face in the desert Southwest. But they're proving to be a valuable tool that can significantly reduce labor demands, cut costs, and help us stay ahead of herbicide resistance (Smith et al., 2021; UC ANR, 2025; NIFA, 2025). The key is figuring out how they fit into your overall management program.
The technology keeps getting better—the AI is getting smarter, the machines are becoming more rugged, and the costs are gradually coming down (NC State Extension, 2025; PMC, 2024; UA ACIS, 2025). Whether you jump in now or wait another season or two, it's worth staying informed about what these systems can and can't do. Come out to the field day in November and see the technology in action. Talk to other growers who are using it. Kick the tires, ask the hard questions, and decide for yourself whether robotic weeders have a place in your operation. We'll see you there.
Don't Miss Out! Register by October 31 to take advantage of the FREE Early Bird Registration. Starting November 1, a registration fee of $75 (plus fees) will be charged. Please Register Here
References
Anthropocene Magazine. (2024, November 28). Are robotic weeders a cost effective part of sustainable farming? Retrieved from https://www.anthropocenemagazine.org/2024/11/are-robotic-weeders-a-cost-effective-part-of-a-sustainable-farming-future/
AZCentral. (2025, May 12). Arizona farmers experiment with AI to improve crop harvests. Retrieved from https://www.azcentral.com/story/news/local/arizona/2025/05/12/arizona-farmers-experiment-ai-to-improve-crop-harvests/76899659007/
Carbon Robotics. (2022, November 10). AI Autonomous Weeder By Carbon Robotics. Telecom Hall Forum. Retrieved from https://www.telecomhall.net/t/ai-autonomous-weeder-by-carbon-robotics/18431
CORDIS. (2024, June 2). A fully autonomous solar-powered lightweight weeding robot, using advanced AI and computer vision. Retrieved from https://cordis.europa.eu/project/id/101166300
Desert Ag Solutions. (2024, November 6). The Desert Difference: A Showcase of AgTech Opportunities for Growing in the Desert. Retrieved from https://desertagsolutions.org/events/desert-difference-showcase-agtech-opportunities-growing-desert
Desert Ag Solutions FarmTech. (2024, December 31). The Desert Difference: FarmTech Connect. Retrieved from https://desertagsolutions.org/events/desert-difference-farmtech-connect
Farmonaut. (2025, June 17). Automated Deserts: Transforming Desert Agriculture In Arizona. Retrieved from https://farmonaut.com/usa/smart-farming-tech-7-ways-it-transforms-arizona-agriculture
Growing Produce. (2023, October 3). Laser Weed Control in the Farm Field: Why Growers Need To Give It Time. Retrieved from https://www.growingproduce.com/vegetables/laser-weed-control-in-the-farm-field-why-growers-need-to-give-it-time/
HowToRobot. (2023, July 16). Weeding robots: redefining sustainability in agriculture. Retrieved from https://howtorobot.com/expert-insight/weeding-robots-redefining-sustainability-agriculture
NC State Extension. (2025, October 27). Artificial Intelligence (AI)-enabled Robotic Weeders in Precision Agriculture. Retrieved from https://content.ces.ncsu.edu/artificial-intelligence-ai-enabled-robotic-weeders-in-precision-agriculture
NIFA. (2025). Automated Machine for Simultaneous Thinning, Weeding and Spot Spraying Lettuce. USDA National Institute of Food and Agriculture. Retrieved from https://portal.nifa.usda.gov/web/crisprojectpages/1000315-automated-machine-for-simultaneous-thinning-weeding-and-spot-spraying-lettuce.html
PMC. (2024, October 29). A novel mechanical-laser collaborative intra-row weeding prototype. Retrieved from https://pmc.ncbi.nlm.nih.gov/articles/PMC11557383/
Smith, R. et al. (2021, February 9). Autonomous Weeders Showing Promise in Lettuce Fields. AgNet West. Retrieved from https://agnetwest.com/autonomous-weeders-showing-promise-in-lettuce-fields/
UC ANR. (2025, March 30). 2020-2021 Evaluations of Automated Weeders in Lettuce Production. University of California Agriculture and Natural Resources, Salinas Valley Agriculture Blog. Retrieved from https://ucanr.edu/blog/salinas-valley-agriculture/article/2020-2021-evaluations-automated-weeders-lettuce-production
UA ACIS. (2025, September 30). Western Growers Case Study – Carbon Robotics LaserWeeder. University of Arizona Agricultural Climate Information Service. Retrieved from https://acis.cals.arizona.edu/agricultural-ipm/vegetables/vipm-archive/western-growers-case-study-carbon-robotics-laserweeder
Western Growers. (2024, September 29). 2024 Desert Difference AgTech Conference. Retrieved from https://www.wga.com/news/2024-desert-difference-agtech-conference/While late instar larvae of beet armyworm (BAW), diamondback moth (DBM), and cabbage looper (CL) can usually be distinguished without difficulty, identifying their eggs and early instars can be challenging, especially when these species occur together on the same hosts, such as the Brassicas. The following descriptions summarize key diagnostic features that can help to accurately identify the eggs and young larvae of these pest species in the field.
Figure 1: Diamondback moth eggs (A) and early instar larva (B).
Figure 2: Cabbage looper eggs (A) and early instar larva (B).
Figure 3: Small cluster of beet armyworm eggs (A),
newly hatched larvae (B), and 3rd instar larva (C).
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Why Water Productivity Matters
Water is one of the most valuable inputs in desert agriculture. Here in Yuma, Arizona, most of our lettuce is irrigated using water from the Colorado River, and every drop counts. One way to measure this efficiency is through Crop Water Productivity (CWP), often called “more crop per drop.”
What is Crop Water Productivity?
CWP tells us how much crop yield we get for each unit of water used.
CWP = Crop Yield/Crop Water Use
A higher CWP means more yield per unit of water an important goal in our desert environment.
Why It’s Important in Yuma
Yuma’s hot, dry, and often windy conditions cause high water loss from soil and plants. Improving CWP helps ensure that every acre-foot of water supports strong, profitable production. Measuring CWP helps identify where we can save water through irrigation timing, soil management, or better agronomic practices.
Physical vs. Economic CWP
CWP can be viewed in two ways:
Physical CWP: How much lettuce (by weight) is produced per unit of water.
Economic CWP: The market value produced per unit of water. What Affects Crop Water Productivity Several factors influence how efficiently crops use water:
Why Compare Organic and Conventional Systems?
Interest in organic lettuce production is growing in the Yuma Valley, but questions remain about its efficiency under desert conditions. Organic systems build soil health with compost and cover crops, which can improve water-holding capacity. However, conventional systems often achieve higher yields due to faster growth and more readily available nutrients. Comparing both systems helps us understand which approach makes better use of limited water resources in Yuma’s unique climate.
Field Study in Yuma Ag Center, 2024–2025
During the 2024–2025 season, a trial was conducted at the Yuma Agricultural Center to measure and compare CWP between organic and conventional iceberg lettuce systems. Both systems were grown under similar conditions using subsurface drip irrigation. This information was used to calculate and compare CWP for each system.
Crop Water Productivity Results
The results from the trial are shown in Figure 1 below. CWP values are expressed as kilograms of lettuce produced per cubic meter of water used (kg/m³). Overall, conventional lettuce produced about 40–50% more yield per unit of water compared to organic systems. This difference was mainly due to stronger plant growth and faster canopy development under conventional fertilization and management. However, organic systems still provide long-term benefits. Healthier soils in organic plots can store more moisture, reduce runoff, and support sustainable water use over time.
Figure 1. Crop Water Productivity (CWP) for organic and conventional iceberg
lettuce systems at the Yuma Ag Center, 2024–2025 season.
Take Home Messages
