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.

I thought I’d change pace this week and take the opportunity to ask you, the readers of this newsletter, if there are any ag automation/mechanization topics you would be interested in hearing more about. I am happy to do some research and share the findings in future articles. Drop me a line at siemens@cals.arizona.edu or feel free to call me at 928.782.5869. I’d love to know your interests.

Fig. 1. Futuristic farming.
(Image credits: AgTech Media Group, Dover, DE)

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

Biological control is one of the key tools for pest management in organic crop production. By maintaining permanent habitats and food sources for the pests’ natural enemies (good bugs) in the vicinity of your farms, you can ensure the continuous availability of the natural enemies. When the growing season starts, the good bugs will be readily available to attack the pests before they become established in the crops. 

Researchers have found that planting a diversity of flowering plants (e.g., sweet alyssum, nasturtium, milkweeds, common cryptantha, hillside vervain, wild petunia, etc.) on a small portion of your farms or the farms’ border can provide adequate food and shelter allowing to maintain abundant and diverse natural enemy species, including syrphid flies, tachinid flies, lacewings, parasitic wasp, etc. that will attack aphids, thrips, lepidopterans, and more. 

As you plan for the next season, please consider planting flowering plants on your farms’ borders or on dedicated patches to conserve natural enemies and enhance your biological control.

 Area wide Insect Trapping Network   VegIPM Update, Vol. 14, No. 21, Oct 18, 2023           
 
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:            
CEW moth increased in Tacna/Roll/Dome last week, and areawide about average for mid-October.
 
Beet armyworm:          
Trap counts highest in Tacna, Wellton and Dome, but below average for October.
 
Cabbage looper:         
Cabbage looper numbers increased in Tacna/Roll/Wellton but still below average.
 
Diamondback moth:    
DBM moths are beginning to appear in traps in Yuma Valley, trending below average for early October.
 
Whitefly:                      
Adult movement increased in the past 2 weeks and above average for mid-October.
 
Thrips:                         
Thrips adult activity down over the past week, and trending below average in October.
 
Aphids:                        
Winged adults continue to be captured for the season, consistent with heavy winds from W-NW. Can expect aphid flights to increase in the coming weeks.
 
Leafminers:                  
Adult activity increased significantly in Tacna associated with maturing melons. Trending above average for mid-October.