Water stressed — Love and Water Deeply 

First person 

 Let’s face it. Leafing, shoot growth and fruiting is a high-stress event for any tree. Suppose other stresses are compounding these other events.  

In that case, this year’s fruit quality or next year’s performance will be impacted significantly. As a tree, ultimately, what you do this year sets it up for success or failure next year. However, there are some stresses you can mitigate now to ensure a good quality fruit this year.  

This year, we all experienced record temperatures in July. Eight days of the month, we experienced over 100-degree temperatures consecutively. And if a tree was already water-stressed, then this weather could have very well caused its demise. Trees must get the right amount of water. The soil texture is vital to telling you how much to apply, how often, how slow, and how deep.   

Water stress during the active growing season can have detrimental effects. Here’s the breakdown of the adverse effects: water stress reduces photosynthesis, reduces transpiration, increases fruit abortion, decreases yield, decreases shoot growth, and decreases trunk growth.  

If you think about water stress in terms of too much water, the effects can be costly and wasteful. Second, too much water creates an anaerobic condition for the roots (especially true in higher clay soils), reduces water and nutrient uptake, increases root suffocation and death, and causes iron chlorosis, stomatal closure, nitrogen leaching, and denitrification. In this way, too much water can affect the whole development process, or life cycle, of a tree as well.  

I was taught long ago that not all tree species’ leaves would wilt and physically show signs of water stress. Pecan trees are one of these species. So, how do we know how thirsty the trees are or how much water is available in the soil?  

Some farmers use a shovel and dig below the soil surface crust to see and feel for themselves. I have seen others and myself use a 4- to 5-foot rebar welded with a handle to push into the soil. If it stops at 1 to 2 feet or can’t push it in at all, they add more water. If it pushes down to 3 feet or more, they hold back.  

There are, of course, more sophisticated devices available too. Soil moisture monitoring tensiometers have been used for a long time and by many. One reason is that they are affordable and of simple design. The disadvantage is that they rely on suction to measure tension or pull on soil water potential; the suction can break, thus making the tensiometer inaccurate and decreasing efficiency.  

There are also electrical resistance blocks that are a little pricier than the tensiometers but are also simple, easy to use, can be left in the field, and will not have to maintain a suction or tension with the soil. The disadvantages are that it needs to consider the soil texture; thus, the irrigation threshold is affected, and it is also inaccurate at saturation.  

The more expensive but highly accurate soil moisture monitoring devices use dielectric methods. These devices can also be connected to dataloggers to keep track of historical data quickly. They can be connected via Bluetooth, internet, or phone to make it accessible from a smartphone or computer. The disadvantages are the price and the need for soil-specific calibration for some models.  

Although these devices are valuable for telling how much moisture is in the soil, they still are limited to the specific area where they are placed. When the root system of a tree is so massive and variable, this limitation can affect the accuracy of your monitoring.  

That’s right! The roots of a tree do not mirror the height and spread of the tree canopy that you see above ground. They extend far more outward than the tree above ground. Some landscapes and farm sites can have more than three or even four different soil types in a given area. Soil texture and conditions greatly influence the readings of these devices as well. In this sense, it is difficult to know or recommend where the measurements should be made; thus, a homeowner, backyard hobbyist, or farm producer may probably need more than one device, creating an even more significant investment.  

Plus, there are situations where the water is there, and the soil is wet, but the trees are still not getting it, such as where there are heavy salt issues in the soil and water. Or the tree’s osmotic potential has been so negatively affected that the tree could be suffering from an embolism in the vascular tissue.   

One of the best, proven methods is by a device called the Scholander Pressure Chamber (aka “pressure bomb,” not to be repeated out loud in an airport)! This device can give a novice user many valuable measurements, such as leaf water potential, predawn leaf water potential, shaded leaf water potential, and midday stem water potential. The measurement of choice for me in the field, especially when taking gas exchange measurements, is the midday stem water potential.   

  

Program announcements   

• Join 4-H! 4-H Enrollment is  open through Jan. 31, 2024. New member registration information can be found by contacting the Extension Office at 505-565-3002 or by email to Sierra Cain at [email protected]
• Ready, Set, GROW! Free gardening classes are being offered virtually. Registration required, please visit the link for upcoming classes and more information visit desertblooms.nmsu.edu/grow.html 
• Valencia County Extension Master Gardeners is Active, Sign up to become one of the next certified Master Gardener’s for Valencia! Classes start January 2024. Please contact Josh Sherman through the Extension Office at 505-565-3002.  
• Healthy Fall Desserts: 9 a.m. to 12 p.m., Tuesday, Nov. 14, the Peralta Methodist Church. Open to Valencia County adults. Create and sample delicious healthy desserts for the holiday season! Cost is $15 per person. Call the office at 505-565-3002 to RSVP or for any questions.  
• Hoop-style Row Cover Workshop, Friday, Nov. 17, at NMSU Los Lunas Agricultural Science Center. Hands-on workshop learning how to design and construct a hoop-style row cover to extend the growing season in the winter. Registration is required. Cost is $15 per person. 
• Santa in the Barn, 10 a.m. to 2 p.m., Saturday, Dec. 2, at the Valencia County Fairgrounds. Come out to Santa’s Barn to play holiday-themed games and check out local holiday crafts from our 4-H program and community members.  
• Winter Kombucha, 10 a.m. to 12 p.m., Wednesday, Dec. 6, at the Valencia County Extension Office.  Open to Valencia County adults. Learn about the health benefits of Kombucha, how to make it at home and take home a start SCOBY! Cost is $10 per person.   
• Soil Health Day: On-Farm Biochar Demonstration, Wednesday, Dec. 6, at Costanza Apple Orchard in Belen. Learn about ways to improve soil health in your farm or garden using different methods and see a live demonstration on how to create your own biochar. Registration is required. Cost is $10 per person. 
• Winter Extravaganza, Friday, Dec. 8. More details to come. Come out and make holiday crafts items and take them home or give as gifts. Cost is $20 per person.  

 Please call or go to our website, valenciaextension.nmsu.edu, for more information.  

If you are an individual with a disability who requires auxiliary aid or service to participate in a program, please contact the Valencia County Cooperative Extension Service Office at 505-565-3002 two weeks in advance of the event.