Root systems provide the foundation for plant development.  At the time of seeding and plant establishment, it is important to monitor and evaluate the newly developing root systems; subsequent plant growth depends on them.  
 
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, including root systems.  Accordingly, root systems have unique characteristics among plants species.  
 
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 matrix and protect 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.
 
The growing point (apical meristem) for the developing root is just behind the root cap and this 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 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.  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 due to 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, which is the foundation for the 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 (Figure 2).
 
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.  
 
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 mineral nutrients and produce soil organic matter.  Turnover of root tissue is an extremely important aspect of plant contributions to soil carbon (C), organic matter, and general soil health.
 
We do not 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 nutrient, water uptake, and structural support is provided through the roots.  
 
It is necessary to sacrifice a few plants occasionally and evaluate root system health and development.  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.

This study was conducted at the Yuma Valley Agricultural Center. The soil was a silty clay loam (7-56-37 sand-silt-clay, pH 7.2, O.M. 0.7%). Spinach ‘Meerkat’ was seeded, then sprinkler-irrigated to germinate seed Jan 13, 2025 on beds with 84 in. between bed centers and containing 30 lines of seed per bed.  All irrigation water was supplied by sprinkler irrigation.  Treatments were replicated four times in a randomized complete block design.  Replicate plots consisted of 15 ft lengths of bed separated by 3 ft lengths of nontreated bed.  Treatments were applied with a CO₂ backpack sprayer that delivered 50 gal/acre at 40 psi to flat-fan nozzles.

Downy mildew (caused by Peronospora farinosa f. sp. spinaciae)was first observed in plots on Mar 5 and final reading was taken on March 6 and March 7, 2025. Spray date for each treatments are listed in excel file with the results.

Disease severity was recorded by determining the percentage of infected leaves present within three 1-ft²areas within each of the four replicate plots per treatment.  The number of spinach leaves in a 1-ft²area of bed was approximately 144. The percentage were then changed to 1-10scale, with 1 being 10% infection and 10 being 100% infection.

The data (found in the accompanying Excel file) illustrate the degree of disease reduction obtained by applications of the various tested fungicides. Products that provided most effective control against the disease include Orondis ultra, Zampro, Stargus, Cevya, Eject .Please see table for other treatments with significant disease suppression/control.  No phytotoxicity was observed in any of the treatments in this trial.

At the UC Cooperative Extension 2024 Automated Technology Field Day in Salinas, CA a couple of weeks ago, 12 of the latest automated and robotic technologies were demonstrated in the field. Most were designed for weed control or thinning vegetable crops. Several of the technologies shown are relatively “new” for the 2024 season. These included laser weeders that also are capable of thinning lettuce (Fig. 1 & 2), a smart cultivator/side-dresser that cultivates between individual crop plants and simultaneously applies fertilizer at a variable rate depending on plant size (Fig. 3), a spot sprayer that utilizes superheated vegetable oil to kill weeds (Fig. 4), and a self-propelled machine that disinfests soil prior to planting using steam. Although the test runs were short, I was impressed with the possibilities for these machines. Company representatives said they will be in Arizona this upcoming season and are interested in meeting with growers. Company contact information can be found at their respective websites, or feel free to contact me if you would like additional information.

Fig. 1. Carbon Robotics’¹ (Seattle, WA) LaserWeeder^TM. The unit utilizes a vision
system to detect crop plants and weeds. A laser is used to kill unwanted plants.
The machine can be used for weeding or thinning lettuce crops (bottom).


Fig. 2. L&A¹ (Chico, WA) autonomous laser weeding/thinning robot. The unit is
equipped with a vision system to detect crop plants and weeds, and a laser to kill
unwanted plants. The machine can be used for crop thinning or weeding (weeded
carrot crop, bottom).


Fig. 3. Stout Industrial Technology’s¹ (Salinas, CA) smart cultivator/side
dresser. The unit is equipped with a vision system for detecting crop plants, and
blades that move in and out of the crop row to remove in-row weeds. Liquid
fertilizer (shown colored with blue dye) is applied at a variable rate depending on
plant size.


Fig. 4. Tensorfield Agriculture¹ (Union City, CA) precision spot spray weeding
machine. The unit has an 80” wide spray boom equipped with 232 individually
controllable spray nozzles to spot spray weeds with superheated vegetable oil
(bottom left, bottom right). A vision system is used to detect weeds and spot
spray resolution is ¼”.


Fig. 5. UA/UC Davis self-propelled band-steam applicator. Device injects steam
into the soil to kill weed seed and soilborne pathogens prior to planting.

[1] Reference to a product or company is for specific information only and does not endorse or recommend that product or company to the exclusion of others that may be suitable.

We did some trials at the University of Arizona Yuma Agricultural Center in broccoli to evaluate and compare Napropamide (Devrinol) liquid formulation 2XT versus the Dry formulation DF-XT. 
This product inhibits the production of fatty acids in plants, which is crucial for plant development. It affects primarily the meristematic cells which are in growing points of the stems and roots. We saw activity especially on seedling development that we show in some pictures at the end of the article. 
Some growers expressed their concern on the safety of different levels of incorporation with sprinkler irrigation. Therefore, we established a test in which we applied the product as a broadcast application after planting. Then we used different levels of incorporation in some sections using 12, 24 and 36 hours of sprinkler irrigation. No difference was observed with the incorporation level in our trial. We observed temporary phytotoxicity from 4-10%. The data was obtained from visual evaluations. Also, a 0.5 to 1” height reduction was exhibited when compared to untreated plots. 
It is common that growers and PCAs make management decisions on herbicide applications in different crops knowing that some injury is expected. Such is the case for alfalfa, wheat, spinach, lettuce and in this case broccoli. Frequently slight stunting it is not noticed because commercial fields don’t have untreated areas for comparison.
We talked to PCA’s and growers at the SW Ag Summit and asked for their experience with napropamide this past season. Some noticed the broccoli exhibited similar levels of phyto, which they considered economically tolerable. 
We noticed that good soil prep was important for before the application of the product and avoiding direct contact of the seed with the product for best results.
On weed control we noticed good activity on nettleleaf goosefoot and lambsquarter. 
At the 45day we collected data counting SMALL and LARGE weeds and at the 60 day evaluation we noticed most of the SMALL goosefoot and lambsquarter in the high rate of napropamide plots stayed small (pic. below).

Results of pheromone and sticky trap catches can be viewed here.

Corn earworm: CEW moth counts down in all traps over the last month; about average for December.

Beet armyworm: Moth trap counts decreased in all areas in the last 2 weeks but appear to remain active in some areas, and average for this time of the year.

Cabbage looper: Moths increased in the past 2 weeks, and average for this time of the season.

Diamondback moth: Adults increased in several locations last, particularly in the Yuma Valley most traps.  Below average for December.

Whitefly: Adult movement remains low in all areas, consistent with previous years 

Thrips: Thrips adult movement continues to decline, overall activity below average for December.

Aphids: Winged aphids still actively moving but declined movement in the last 2 weeks. About average for December.

Leafminers: Adult activity down in most locations, below average for this time of season.