Soils with excess soluble salts, saline soils, and/or excess sodium (Na⁺) concentrations (sodic) are a natural feature of desert soils and common in arid land agriculture.  This is primarily due to an accumulation of soluble salts near the soil surface as water evaporates from the soil surface.
 
Saline soils are a problem in crop production systems because of the sensitivity to salinity of crop plants, although plants vary in their degree of sensitivity.  The period of greatest plant sensitivity to salinity is in the early stages of development, during germination and stand establishment.
 
Sodic soils are a problem in crop production systems because of the adverse effects of excess sodium on soil structure, causing a dispersion of soil particles and the breakdown of soil aggregates.  This leads to poor water infiltration and percolation in the soil profile.
 
Some basic points associated with saline and/or sodic soils and management are outlined in the following sections.
 

1. Saline soils have an electrical conductivity of the soil solution (extract, EC_e) of EC_c > 4 dS/m.  Functionally, saline soils have sufficient soluble salts to interfere with and diminish plant growth and development.
   1. Soil salinity is a relative term or condition based on the critical salt sensitivity levels of the crop plant in question.
   2. Plants vary tremendously in their degree of salt tolerance.
   3. Reclamation and management of soil salinity requires an understanding of the specific level of sensitivity of the target plant to salinity.
   4. Saline soils commonly have good soil aggregation and structure.
   5. Reclamation of saline soils requires sufficient water to accomplish leaching and the removal of soluble salts.  Thus, good internal soil drainage is important.

 

1. Sodic soils have a high level of exchangeable sodium (Na⁺) on the soil cation exchange complex (CEC).  Sodic soils have an Exchangeable Sodium Percentage, ESP > 15 of the soil CEC or a sodium adsorption ratio, SAR > 13 from the soil extract.
   1. Sodic soils commonly have poor soil structure and aggregation due to the dispersed condition of soil particles caused by high concentrations of Na on the CEC.
   2. In practice, finer textured soils, e.g. clay, clay loam, silty clay loam, etc. with high clay content can develop sufficient dispersion and poor soil structure at ESP or SAR levels ~ 6-10.  So, the ESP and SAR designations are general and not absolute.

https://www.nrcs.usda.gov/wps/PA_NRCSConsumption/download/?cid=nrcseprd589210&ext=pdf
Sodic soil reclamation does require an amendment that will facilitate the chemical exchange of Na⁺, usually from a calcium (Ca²⁺) source, such as gypsum (CaSO₄).
 

1. Reclamation for saline soils requires additional irrigation water for leaching.  Chemical amendments are not necessary for soluble salt removal.

An effective and straightforward method of calculating a leaching requirement (LR) can be calculated with the following equation that was presented by the USDA Salinity Laboratory (Ayers and Westcot, 1989).
Leaching Requirement (LR) Calculation:

Where: 
ECw = salinity of the irrigation water, electrical conductivity (dS/m)
ECe = critical plant salinity tolerance, electrical conductivity (dS/m)

1. Saline soils do NOT need amendments for reclamation or management.  Only leaching is needed.

 

1. Sodic soil reclamation involves a two-step process:

1. Exchange of Na with Ca and 2) leaching of soluble Na⁺ from the crop root zone.

 

1. Adequate soil leaching is required in both cases of saline and sodic soils.
   1. In the case of sodic soil reclamation, the leaching needs to occur after appropriate amendment applications for Na⁺ exchange with a suitable cation such as Ca²⁺.

 

1. Adequate drainage is necessary to accomplish sufficient leaching of solutes through the soil profile and below the root zone in the reclamation of both saline and sodic soils.

 

1. Irrigation systems capable of delivering sufficient water for leaching are necessary.
   1. Level basin flood irrigation best serves salinity leaching requirements.
   2. Sufficient salinity leaching can be accomplished with furrow flood or overhead sprinkler irrigation.
   3. Drip irrigation systems much be designed to provide sufficient volumes of water to accomplish adequate soil leaching.

i.Drip irrigation systems are commonly very limited in this respect.
 

1. Crop rotation systems are important in leaching and salinity management.
   1. For example: Crops planted on the flat and irrigated by level basin irrigation serve to facilitate good salinity leaching in a field.

i.Examples: wheat, alfalfa, sudangrass, etc.
 

1. Good field observations of crop growth and development in conjunction with regular soil and water sample analysis are key elements to the management of salinity and sodicity in agricultural fields.  

For example, young plants in the germination and seedling stages of development are most susceptible to salinity and water stress.  Abnormal amounts of seedling damage and/or difficulties in germination can often be early signs of increasing soil salinity.
Also, early signs of increasing salinity are often observed with plants demonstrating water stress with plant-available water levels in the soil that should seemingly be adequate for maintaining non-stressed plants.  Thus, fields that are requiring an irrigation in shorter intervals than usual can possibly be an early sign of increasing salinity and it is good to follow-up with a good set of soil samples and a sample of the irrigation water to check.
Early identification of problems in the field with increasing Na concentrations are commonly noticed with increasing tendencies of the soils in the field to form surface crusts very easily, which reduces water infiltration into the soil surface.  This is often recognized at the time planting and stand establishment with germination problems resulting from increasing degrees of soil crusting.

It’s unfortunately a very great season to be a plant pathologist…

We have confirmed the first sample of Fusarium wilt on lettuce submitted to the Yuma Plant Health Clinic from Yuma County. The stunted seedlings looked like any other typical case of damping-off at the seedling stage. When plated on culture media, subsequently confirmed Fusarium colonies grew abundantly from the declining plant tissues. If you’re not already on guard and scouting, this is a warning that Fusarium is active in Yuma County.

Adding on to this early alert, we’ve received a surge of submissions of young brassicas to the clinic. Several severely wilted and declining plants from around Yuma County have cultured positive for Pythium, likely as an opportunistic invader coming in on the back of all the early-season rain that brought stress to seeds and young transplants. Growers may want to consider oomycides, but only if the seedling disease is first confirmed to be Pythium. Remember, many seedling diseases caused by true fungi are indistinguishable from those caused by Pythium.

If you have any concerns regarding the health of your plants/crops please consider submitting samples to the Yuma Plant Health Clinic for diagnostic service or booking a field visit with me:

 

Chris Detranaltes
Cooperative Extension – Yuma County
Email: cdetranaltes@arizona.edu
Cell: 602-689-7328
6425 W 8th St Yuma, Arizona 85364 – Room 109

Interested in staying up to date on the latest robotic ag technologies? The International Forum for Agricultural Robotics, FIRA, hosts two annual conferences focusing on robotics and autonomous farming solutions, one in Europe and one in the USA. They recently uploaded recordings of sessions from the 2024 World FIRA, held in Toulouse, France to YouTube. The site also contains playlists of themed breakout sessions from previous European and USA events (over 400 videos total). Highlights include panel discussions with growers and company executives, robot demos, and inno’pitches from startup companies. Most of the content, particularly from the USA events, is high quality and worth viewing. 
Check it out by clicking here or on the image below.

There are many different types of pests that affect crops grown in Arizona. The three types of pests most often cited as the source of most problems are insects, diseases and weeds. These are the same types of pests that are cited as causing the major agricultural pest problems across the U.S. and worldwide. Graphs 1-3 illustrate, however, that the relative importance of these types of pest problems differ in Arizona from the rest of the U.S. and worldwide. In terms of pesticide use, worldwide herbicides accounted for 36% of total usage, insecticides 25%, and fungicides 10% and other 29% (nematicides, rodenticides, fumigants, bird, fish and aquatic pests). In the U.S., herbicides accounted for 44%, insecticides 10%, fungicides 6%, and other 40% of pesticide use. In Arizona, however, insecticides accounted for 58%, herbicides 17% and fungicides 12%. This is only an indirect measure of the relative importance of these three areas of pest management and may be heavily influenced by the amount of pesticides used. For instance, it is common to spray for insects five or more times per season while it is uncommon to spray for weeds more than twice. None the less, these graphs illustrate that weeds are the predominant pest problem in agricultural areas across the U.S. and worldwide.

We wanted to share the information above obtained from the PCA Study Guide Section VI prepared by our "amigo" Barry Tickes who is teaching the Applied Weed Science Class at the University of Arizona this semester.

This time of year, John would often highlight Lepidopteran pests in the field and remind us of the importance of rotating insecticide modes of action. With worm pressure present in local crops, it’s a good time to revisit resistance management practices and ensure we’re protecting the effectiveness of these tools for seasons to come. For detailed guidelines, see Insecticide Resistance Management for Beet Armyworm, Cabbage Looper, and Diamondback Moth in Desert Produce Crops .

VegIPM Update Vol. 16, Num. 20

Oct. 1, 2025

Results of pheromone and sticky trap catches below!!

Corn earworm:  CEW moth counts declined across all traps from last collection; average for this time of year.

Beet armyworm: BAW moth increased over the last two weeks; below average for this early produce season.

Cabbage looper: Cabbage looper counts increased in the last two collections; below average for mid-late September.

Diamondback moth: a few DBM moths were caught in the traps; consistent with previous years.

Whitefly:  Adult movement decreased in most locations over the last two weeks, about average for this time of year.

Thrips: Thrips adult activity increased over the last two collections, typical for late September.

Aphids: Aphid movement absent so far; anticipate activity to pick up when winds begin blowing from N-NW.

Leafminers: Adult activity increased over the last two weeks, about average for this time of year.