There are more than 100 chemical elements known to man today.  However, only 16 have been proven to be essential for plant growth.  The essential elements for plant growth are in the upper portions of the periodic table with lower atomic numbers, indicating the lighter and more volatile elements that are in higher concentrations closer to the earth’s surface and part of the rocks that commonly serve as the parent materials for soils.
 
For a nutrient to be classified as essential, certain rigid criteria must be met.  These criteria are as follows (Havlin, et al., 2014; Troeh and Thompson, 2005; Weil and Brady, 2017; Warren et al., 2017):
 

1. The element is essential if a deficiency prevents the plant from completing its vegetative or reproductive cycle.
2. The element is essential if the deficiency in question can be prevented or corrected only by supplying the element.
3. The element is essential if it is directly involved in the nutrition of the plant and is not a result of correcting some microbiological or chemical condition in the soil or culture media.

 
The essential elements and their chemical symbols are listed in Table 1.  Three of the 16 essential elements – carbon, hydrogen and oxygen – are supplied mostly by air and water.  These elements are used in relatively large amounts by plants and are non-mineral, often referred to as organic nutrients and they are supplied to plants by carbon dioxide and water. 
 
The other 13 essential elements are mineral elements and must be supplied by the soil and/or fertilizers.  Not all are required for all plants, but all have been found to be essential to some (Tisdale & Nelson).
 
 
 
Table 1.  Essential plant nutrients, chemical symbols, and sources.

Mostly from air and water (non-mineral)	Mostly from air and water (non-mineral)	From soil and/or fertilizers (mineral)	From soil and/or fertilizers (mineral)	From soil and/or fertilizers (mineral)	From soil and/or fertilizers (mineral)
Element	Symbol	Element	Symbol	Element	Symbol
Carbon	C	Nitrogen	N	Iron	Fe
Hydrogen	H	Phosphorus	P	Manganese	Mn
Oxygen	O	Potassuim	K	Zinc	Zn
		Calcium	Ca	Copper	Cu
		Magnesium Mg	Mg	Boron	B
		Sulfur	S	Molybdenum	Mo
				Cholorine	Cl

 
 
The essential plant nutrients may be grouped into three categories.  They are as follows:
 

1. Primary nutrients - nitrogen, phosphorus and potassium
2. Secondary nutrients - calcium, magnesium and sulfur
3. Micronutrients - iron, manganese, zinc, copper, boron, molybdenum, and chlorine

 
This grouping separates the elements based on relative amounts required for plant growth and is not meant to imply any element is more essential or important than another (Troeh and Thompson, 2005; Weil and Brady, 2017; Warren et al., 2017).
 
Primary Non-Mineral Nutrients: Carbon, Hydrogen and Oxygen
Carbon is the backbone of all organic molecules in the plant and is the basic building block for growth.  After absorption of carbon dioxide (CO₂) by the leaves of the plant, carbon is transformed into carbohydrates by combining with hydrogen and oxygen through the process of photosynthesis.
 
Metabolic processes within the plant transform carbohydrates into amino acids and proteins and other essential components.
 
The essentiality of all mineral nutrients is associated with their use in structural plant components and/or physiological and biochemical reactions associated with essential processes in plant growth and development.  Plants cannot complete the life cycle if they are deficient in an essential nutrient.
 
References
Havlin, J.L., Beaton, J.D., Tisdale, S.L. and Nelson, W.L. 2014. Soil Fertility and Fertilizers; An Introduction to Nutrient Management. 6th Edition, Prentice Hall, Upper Saddle River, NJ.
Troeh, F.R. and Thompson, L.M. (2005) Soils and Soil Fertility. Sixth Edition, Blackwell, Ames, Iowa, 489.
Warren, J., H. Zhang, B. Arnall, J. Bushong, B. Raun, C. Penn, and J. Abit. Oklahoma Soil Fertility Handbook. Published Apr. 2017; Id: E-1039
Weil, R.R. and Brady, N.C. (2017) The Nature and Properties of Soils. 15th Edition, Pearson, New York.

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.

We are in the process of organizing The Desert Difference: A Showcase of AgTech Opportunities for Growing in the Desert. The two-day event will be held November 13-14^th in Yuma, AZ. The first day will be a Field Day, the second will be a standard conference with keynote speakers and breakout sessions. Details of the conference will be coming soon. The focus of this article is the Field Day. As with our previous AgTech Field Days, the workshop will feature the latest ag technologies being demonstrated in the field. I’ve been reaching out to multiple companies but am sure I’m not aware of all the cutting-edge technologies out there. We would like to showcase as many innovative ag technologies as possible, so please contact me if you are interested in demoing your equipment or know someone that is. It’s an open invitation - private companies, and university and government researchers are all welcome!

Fig. 1. Previous University of Arizona AgTech Field Days.

We promised to publish your comments on the last article on Napropamide. Your honest opinion is welcomed, and we understand that sometimes your views and experiences will differ from ours.

You have reported that uniformity of broccoli harvesting was affected by the application of Napropamide. Having too many harvesting events can obviously increase the cost of your operations. 

Thank you for communicating this to us. According to some authors in crops such as wheat yield can be improved by minimizing plant-to-plant variability in seedling emergence¹. We value your perspective as we are all working for the benefit of the industry. 

The evaluations conducted at the UA Yuma Agricultural Center were not taken to harvest and therefore no crop maturity data was collected this season. Hopefully will do this in future trials. 
 
Other comments: 
“Thanks for the Devrinol trial work. I had almost forgot about this material. We used to use it on Cantaloupe and Tomatoes up here years ago. I recall one experience where a new grower used it under plastic and suffered high plant stunting and death. In most cases in open furrow production, it worked great”. –PCA/Grower
 
“I reduced the rate to 1pt and worked good”. --PCA

Note on Dacthal
We wanted to share some information on the revision of the registration of DCPA. 
On April 1, 2024 the EPA published new information on Dacthal here:  EPA publication on DCPA released yesterday. It was a warning that has been posted in various web sites.

Previously on March 27, 2024 response (EPA-HQ-OPP-2011-0373-0112) to the registrant the EPA says the following: “Given our inability to identify and agree on a mitigation strategy that addresses EPA’s concerns, the agency is currently exploring the regulatory options available to it under FIFRA Section 6. Due to the serious potential risks posed by DCPA use, EPA will be pursuing these regulatory options as soon as practicable.” Therefore, we are awaiting final decision.
Some members the industry are expecting this herbicide to be available this season.  The Vegetable IPM Team encourages you to  check the latest information following the link :https://www.regulations.gov/docket/EPA-HQ-OPP-2011-0374/document?postedDateFrom=2024-04-01&postedDateTo=2024-04-03

Thank you very much for your comments they are very useful and beneficial for the industry.
 
 
 
 References

1. https://cdnsciencepub.com/doi/10.4141/cjps95-098

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.