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 and the process is driven largely by the intense evaporative demand from the arid desert environment.
A saline soil is a problem in crop production systems because of the sensitivity of crop plants to salinity, 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.
A sodic soil is 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.
The development of saline and sodic conditions does not happen rapidly; the symptoms are commonly slow and hard to see in their development, until they are a problem. Thus, two things are important for field management: 1) regular soil samples and 2) field observations of crop and soil conditions.
Some fundamental points regarding the management of saline and/or sodic soils are outlined in the following section.
1. A saline soil by definition has an electrical conductivity of the soil solution (extract, ECe) of ECc ≥ 4 dS/m. Functionally and practically, saline soils have sufficient soluble salts to interfere with and diminish plant growth and development.
a. Soil salinity is a relative term or condition based on the critical salt sensitivity levels of the crop plant in question.
b. Plants vary tremendously in their degree of salt tolerance.
c. Reclamation and management of soil salinity requires an understanding of the specific level of sensitivity of the target plant to salinity.
d. Saline soils commonly have good soil aggregation and structure.
e. Reclamation of saline soils requires sufficient water to accomplish leaching and the removal of soluble salts. Thus, good internal soil drainage is important.
2. Sodic soils have a high level of exchangeable sodium (Na+) on the soil cation exchange complex (CEC). Sodic soils by definition have an Exchangeable Sodium Percentage, ESP > 15 of the soil CEC, or a sodium adsorption ratio, SAR > 13 from the soil extract (calculated).
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).
3. Reclamation for saline soil 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)
4. Saline soils do NOT need amendments for reclamation or management. Only leaching is needed.
5. 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.
6. Adequate soil leaching is required in both cases of saline and sodic soils.
a. 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+.
7. 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.
8. Irrigation systems capable of delivering sufficient water for leaching are necessary.
9. Crop rotation systems are important in leaching and salinity management.
10. 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 showing signs of water stress and require 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.
11. As demonstrated by the LR calculation in point 3, water quality is an important factor in the management of soil salinity. The soil chemical environment will develop an equilibrium condition in relation to irrigation water quality (salinity content) and field management. The soil solution will have a definite chemical signature from the irrigation water being applied.
12. Soil drainage is an important factor in the management of soil salinity and sodicity. Good drainage is essential for the leaching and removal of soluble salts and the leaching and removal of excess sodium in the case of a sodic soil.
I hope you are frolicking in the fields of wildflowers picking the prettiest bugs.
I was scheduled to interview for plant pathologist position at Yuma on October 18, 2019. Few weeks before that date, I emailed Dr. Palumbo asking about the agriculture system in Yuma and what will be expected of me. He sent me every information that one can think of, which at the time I thought oh how nice!
When I started the position here and saw how much he does and how much busy he stays, I was eternally grateful of the time he took to provide me all the information, especially to someone he did not know at all.
Fast forward to first month at my job someone told me that the community wants me to be the Palumbo of Plant Pathology and I remember thinking what a big thing to ask..
He was my next-door mentor, and I would stop by with questions all the time especially after passing of my predecessor Dr. Matheron. Dr. Palumbo was always there to answer any question, gave me that little boost I needed, a little courage to write that email I needed to write, a rigid answer to stand my ground if needed. And not to mention the plant diagnosis. When the submitted samples did not look like a pathogen, taking samples to his office where he would look for insects with his little handheld lenses was one of my favorite times.
I also got to work with him in couple of projects, and he would tell me “call me John”. Uhh no, that was never going to happen.. until my last interaction with him, I would fluster when I talked to him, I would get nervous to have one of my idols listening to ME? Most times, I would forget what I was going to ask but at the same time be incredibly flabbergasted by the fact that I get to work next to this legend of a man, and get his opinions about pest management. Though I really did not like giving talks after him, as honestly, I would have nothing to offer after he has talked. Every time he waved at me in a meeting, I would blush and keep smiling for minutes, and I always knew I will forever be a fangirl..
Until we meet again.
Hi, I’m Chris, and I’m thrilled to be stepping into the role of extension associate for plant pathology through The University of Arizona Cooperative Extension in Yuma County. I recently earned my Ph.D. in plant pathology from Purdue University in Indiana where my research focused on soybean seedling disease caused by Fusarium and Pythium. There, I discovered and characterized some of the first genetic resources available for improving innate host resistance and genetic control to two major pathogens causing this disease in soybean across the Midwest.
I was originally born and raised in Phoenix, so coming back to Arizona and getting the chance to apply my education while helping the community I was shaped by is a dream come true. I have a passion for plant disease research, especially when it comes to exploring how plant-pathogen interactions and genetics can be used to develop practical, empirically based disease control strategies. Let’s face it, fungicide resistance continues to emerge, yesterday’s resistant varieties grow more vulnerable every season, and the battle against plant pathogens in our fields is ongoing. But I firmly believe that when the enemy evolves, so can we.
To that end I am proud to be establishing my research program in Yuma where I will remain dedicated to improving the agricultural community’s disease management options and tackling crop health challenges. I am based out of the Yuma Agricultural Center and will continue to run the plant health diagnostic clinic located there.
Please drop off or send disease samples for diagnosis to:
Yuma Plant Health Clinic
6425 W 8th Street
Yuma, AZ 85364
If you are shipping samples, please remember to include the USDA APHIS permit for moving plant samples.
You can contact me at:
Email: cdetranaltes@arizona.edu
Cell: 602-689-7328
Office: 928-782-5879
Thank you all very much. I look forward to meeting you all soon.
Biological control is a crucial tool for managing pests in organic crop production. Arthropod natural enemies provide significant ecosystem services that favor the suppression of agricultural insect pest populations. When you maintain permanent habitats and food sources for the natural enemies of pests in the vicinity of your farms, it favors 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. 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.
Figure 1. Insectary plants planted in field margins to attract and conserve natural enemies.
Figure 2. Some suggested insectary plants.
Intercropping, the practice of growing different crops in the same field, is also a suitable agricultural practice for managing insect pests because landscape diversity plays a crucial role in biodiversity conservation and sustainable pest management. Crops grown in intercropping systems are more likely to be less injured than those grown in monoculture. The non-host companion plants can have repellent or deterrent properties that act against insect pests that attack the main crop. Companion plants can also trap the pests, reduce their ability to locate the host plant, and increase the abundance of natural enemies. Like in a push-pull intercropping system, your main crop is intercropped with plant species that can make it less visible or can emit undesirable volatiles (smells) that divert the pests away from the main crop, on the other hand, other plants in your intercropping system can be extremely attractive using stimuli that are highly apparent and attractive to the pest, hence trapping the pest (Fig. 3). Insects use visual, chemical, or tactile cues to locate their host. Thus, by intercropping the main crop with plants that emit more attractive scents, which are more visually appealing, or can release undesirable odors to the pests, we can reduce the abundance and impact of the pest on the main crop.
Figure 3. Pictorial representation of push-pull strategy.
In Brazil, the push-pull strategy has been found effective in managing major kale pests. They found that using mustard as a preferred host pulled the pests away from the kale crops, while marigold plants increased the beneficial arthropod population, which provided additional control of the pests. In Salinas, California, intercropping lettuce with sweet alyssum has favored some measurable aphid control. Sweet alyssum attracts and feeds hoverflies, which then lay eggs in lettuce, producing hoverfly larvae that consume aphids (Fig. 4).
Figure 4. Graphical representation of Lettuce-Alyssum intercropping system for aphids
control. (Image source: Brannan 2013).
As you plan for the next season, you can consider planting flowering plants along the borders of your farms or in dedicated patches to conserve natural enemies and enhance your biological control. When feasible, consider intercropping multiple crop species that are not affected by the same pests; this will reduce the abundance of insect pests and also increase the abundance and diversity of beneficial insects.
Weed management is one of the most significant challenges in organic production systems, especially in high-value leafy greens like lettuce. With limited tools available, growers should combine strategies to suppress weeds effectively. One approach is precision irrigation management. By delivering water directly to the crop root zone through systems like subsurface drip irrigation, growers can reduce soil surface wetting, making conditions less favorable for weed germination. Yuma’s organic growers are doing a pioneering job in adopting these strategies, and when paired with sensor-based irrigation scheduling, the practice not only conserves water but also helps disrupt the weed life cycle.
Read my recently published Extension article for the full details: Can Precision Irrigation Be an Effective Approach to Suppress Weed Pressure in Organic Lettuce?
