- Author: Dani Lightle
This article first appeared in Sacramento Valley Orchard Source
Missing the Target: Why you Should Irrigate Potted Trees Directly onto Potting Media
or
Why Emitters Should be Placed on the Root Ball at Planting
Dani Lightle, UCCE Orchards Advisor, Glenn Butte & Tehama Counties
N.B. potted trees are standard commercial container grown citrus and avocado trees
Generally, when I am working with growers on a problem related to potted-tree establishment, the cause is lack of water movement into the potted media, creating tree stress. This results from the difference in soil particle size at the boundary between the orchard soil and the tree's potting soil. When you plant a potted tree in your orchard, it has a substrate – some mix of peat and vermiculite – that is very different than your soil type. The change in texture and pore size inhibits water movement from the surrounding soil into the potting media. As a result, Irrigation water applied outside the potted soil media isn't getting to the roots.
The sequence of photos in Figure 1 demonstrates this phenomenon. I set up a mock orchard condition with soil (Tehama series silty loam) next to a potted tree (potting soil) in a ½ inch wide frame. I then slowly added water to match the soil infiltration rate, similar to a drip emitter, approximately 4 inches away from the potting soil in the ‘orchard' soil.
You will see that the water does not move into the potting soil (Figure 1C & D). Two forces – gravitational pull and capillary action – move water downward and laterally in the soil. Since the potting soil is not below the orchard soil, gravity does not move water into the potting soil. Capillary action is not strong enough to move water into the potting soil because the difference in pore size is too great. So, irrigation water goes where it can easily flow – downwards and laterally into dry, native soil but not into the potting soil. More water does not solve the problem, it will just move past your newly planted trees and wet more native soil.
For about the first month of growth, irrigation emitters should be located at the base of the potted tree to ensure the potting medium receives water. Frequently check to ensure that the potting soil stays wet – not the soil somewhere else in the tree row or mound – before, after, and between irrigation sets. The best way to do this is with a small trowel and your hands. Water will need to be applied at the base of the tree until the tree roots grow beyond the potting soil and into your orchard's native soil. The time required for this to happen will vary depending on factors such as temperature, but it should take roughly a month.
Figure 1. This sequence of photos shows the movement of water applied to Tehama series silty-loam soil. Water was applied at the blue arrow, approximately 4 inches from the potting soil. Total elapsed time was 51 minutes. Water moved downwards and laterally but did not cross the boundary into the potting soil.
- Author: Ben Faber
Presented by
California Avocado Society, Inc., California Avocado Commission, and University of California Cooperative Extension
California Avocado Growers Seminars Series 2018
Scheduled Dates and Topics
February Seminar Topic
Pest Monitoring and Management
Speakers:
Tuesday, February 6, 2018, 1:00 p.m. to 3:00 p.m.,
UC Cooperative Extension Office Auditorium, 2156 Sierra Way, San Luis Obispo, CA 93401
Wednesday, February 7, 2018, 9:00 a.m. to 11:00 a.m.,
UC Cooperative Extension Office Auditorium, 669 County Square Dr. Ventura, CA 93003
Thursday, February 8, 2018, 1:00 p.m. to 3:00 p.m.,
Fallbrook Public Utility District Board Rm., 990 East Mission Rd. Fallbrook, CA 92028
April Seminar Topic
Old and New Smart Agriculture
Speakers:
Khaled Bali: Irrigation Specialist, Kearney REC
Alireza Pourreza: Ag Engineer, UC Davis
Tim Spann: California Avocado Commission Research Program Director
Dates/Times/Locations:
Tuesday, April 17, 2018, 1:00 p.m. to 3:00 p.m.,
UC Cooperative Extension Office Auditorium, 2156 Sierra Way, San Luis Obispo, CA 93401
Wednesday, April 18, 2018, 9:00 a.m. to 11:00 a.m.,
UC Cooperative Extension Office Auditorium, 669 County Square Dr. Ventura, CA 93003
Thursday, April 19, 2018, 1:00 p.m. to 3:00 p.m.,
Fallbrook Public Utility District Board Rm., 990 East Mission Rd. Fallbrook, CA 92028
June Seminar Topic
Irrigation: Selection of Sensors, Emitters, Injectors and Reading Water Reports
Selection of sensors, emitters
Dates/Times/Locations:
Tuesday, June 5, 2018, 1:00 p.m. to 3:00 p.m.,
UC Cooperative Extension Office Auditorium, 2156 Sierra Way, San Luis Obispo, CA 93401
Wednesday, June 6, 2018, 9:00 a.m. to 11:00 a.m.,
UC Cooperative Extension Office Auditorium, 669 County Square Dr. Ventura, CA 93003
Thursday, June 7, 2018, 1:00 p.m. to 3:00 p.m.,
Fallbrook Public Utility District Board Rm., 990 East Mission Rd. Fallbrook, CA 92028
August Seminar Topic
Grower Seminar and Field Tour
Details to come.
Dates/Times/Locations: One site only
Wednesday, August 1, 2018, 10:00 - 2:00 p.m.,
South Coast Research & Extension Center Conference Room, 7601 Irvine Blvd., Irvine, CA 92818
- Author: Ben Faber
There's a new Topics in Subtropics Newsletter available:
- Ah, Rats! ?
- So You Want To Install Soil Moisture Meters? ?
- Notes on Applying Gibberellic Acid (GA) to Navels in
the Southern San Joaquin Valley of California ? - Fall Leaf Tissue Sampling ?
- FREE! Citrus: UC IPM Pest Management Guidelines
http://ceventura.ucanr.edu/newsletters/Topics_in_Subtropics71533.pdf
Subscribe:
http://ceventura.ucanr.edu/news/Topics_in_Subtropics/
- Author: Ben Faber
My dad always said that if you can learn one good thing from a meeting, it was a good meeting. Here's a webinar that might offer something good to for tree growers. Listen in and make up your mind.
Webinar: California & Chile: Opportunities for Precision Agriculture in Climate Change Adaptation and Mitigation.
Agenda & Speakers
Introduction
- Dr. Amrith Gunasekara, Science Advisor to the Secretary, CDFA
Opening Remarks
- Dr. Pablo Zamora, Associate Director, UC Davis Chile
- Marcela Rondon, Agricultural Attaché , USDA FAS
Panel 1: Innovation in precision agriculture
- Dr. Tom Shapland, Co-founder and CEO, Tule Technologies
- Andreas Neuman , President, UAV IQ
Panel 2: Seeing it in action: Operations that have successfully adopted precision ag tech
- Allison Jordan, Vice President of Environmental Affairs, Wine Institute
- John Erb, Vice President for Sustainable Communities and Resource Solutions, Driscoll's
- Dr. Alvaro Gonzalez, R&D Assistant Manager of the Center for Research & Innovation, Concha Y Toro
Panel 3: Looking ahead: Promising research into the world of precision agriculture
- Dr. Chandra Krintz, Professor, UC Santa Barbara
- Dr. Carlos Flores, Program Coordinator Agronomy and Environment , UC Davis Chile
Register here:
https://register.gotowebinar.com/register/2276456747899022083
- Author: Ben Faber
So, every few weeks the question comes up of whether to install soil moisture meters which leads to the question of which to buy and install or have installed. And then come the questions of what do the readings mean and why aren't the readings consistent. Or maybe this question arrives after the grower has installed the sensors or system and the values don't conform to a known or knowable pattern.
The first question to the grower is why they want to install soil moisture sensors or a system. Everyone has a different answer which I've always found interesting. Usually it boils down to having more or better information, although it's hard to beat a good old soil auger. Which takes time and labor.
So once that is cleared up, it comes down to what area they want to monitor. Is it an acre, 10 acres, 50 acres, 100 acres, 200 acres, 1,000 etc.? What are the different irrigation blocks, soil types, aspects? How complex is the area that is to be monitored? Do they need one monitoring site or many? Can the information be gathered in the field, or does it need to be accessed from a distance? Linked by hardwire, infrared, cell phone, wifi, satellite, etc.?
Then the question is does the grower do the installation or is it done by a company? And then whatever the case is, who maintains the system and for that matter, who maintains the information? What software is used and who interprets it?
And what sensors are being used: tension, electrical resistance, conductance, capacitance, electromagnetic…….? The list seems to go on and there are no models and brands coming out on a regular basis. And how reliable are the sensors? What's their lifespan? And what are they measuring and in what units? How affected are the readings by salinity and what soil volume are they measuring? And how important is their placement?
This last point is so often overlooked. The sensor needs to be in the active root zone where water is being taken up. Not where it's convenient to read, not where the plants cant use the water. Placement is so often overlooked.
And then how much do you want to spend? $100 per installation, $1000? With a monthly or yearly maintenance fee or none? Who responds when there are problems?
Wow, so yeah, there are lots of questions. Here's a chart that might help categorize some of the questions:
Method |
Cost |
Ease of use |
Accuracy |
Reliability |
Salt-affected |
Stationary |
Gypsum block |
L |
H |
H |
H |
L |
YES |
Tensiometer |
L |
M |
H |
M |
L |
YES |
Portable tensiometer |
M |
M |
H |
M |
L |
NO |
Solid-state tensiometer |
M |
H |
H |
H |
L |
YES |
Time domain reflectometer |
H |
M |
H |
H |
M |
BOTH |
Neutron probe |
H |
L |
H |
H |
L |
YES |
Feel (soil probe) |
L |
H |
H |
H |
L |
NO |
Gravimetric (oven) |
L |
M |
H |
H |
L |
NO |
Conductance |
L |
H |
M |
M |
H |
BOTH |
Capacitance |
M |
H |
M |
H |
M |
BOTH |
H, high; M, medium; L, low
And the good Almond Doctor might help some more:
http://thealmonddoctor.com/2015/07/10/soil-moisture-sensing-systems/
And maybe some of these publications can help sort out what questions to ask
http://calag.ucanr.edu/Archive/?article=ca.v054n03p38
http://calag.ucanr.edu/Archive/?article=ca.v054n03p47
http://anrcatalog.ucanr.edu/Details.aspx?itemNo=21635
Khaled Bali, our Irrigation Specialist at Kearney Research and Education Center near Fresno, is part of a group in the process of evaluating different types and models of soil moisture sensors. He should have a publication that can more accurately sort through the many sensor choices that are available at this time. But in time, there should be more models on the market and new update will be necessary.
The question, though, is to ask yourself how irrigation is being done and how it can be improved. The basics of design, maintenance, distribution uniformity and how scheduling is being currently done – when and how much to apply. Definitely, soil moisture sensors can help, but you gotta know how to use them and maintain them, just like the whole irrigation system.
A grower who uses tensiometers told me that people think of soil sensors as though they were reading a book. Something cut and dried. A simple plot line that you follow. Irrigation is not a book. There are many other subplots to irrigation than just reading the digital face. Looking at the weather, evapotranspiration, the tree, how fast the moisture is depleted, how deep the moisture is being pulled from all contribute to the "sensors" used to irrigate. Use them all. Even though this grower has irrigators on 250 acres of trees, he also checks the orchard tensiometers at least once a week on his own to confirm all of his senses.