Optimizing your Christmas trees irrigation with soil tensiometers

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Snow is quickly melting and we are all getting prepared for the new growing season. Even though we have lots of moisture now, last year’s dry growing season is not far from our thoughts.

One very useful tool for irrigation scheduling in Christmas tree production is a soil tensiometer. A soil tensiometer is a device used to measure the soil matric potential, which is basically the amount of vacuum that trees’ roots are applying to absorb water from the soil. Tensiometers are sold as 12-inch, 18-inch and 24-inch, and the one you elect to use in your system will depend on your soil depth and the age and size of your trees. We recommend using 12-inch tensiometer for fields with trees less than five feet tall. If you are thinking about installing tensiometers this spring, you should be looking for a vendor now and ordering them before the season goes into full swing. You will also need some time to familiarize yourself with them and become comfortable using them.

Your tensiometer devices should be placed in the drier spots in your fields and you should install several to make sure that the entire field is well covered. Ideally, install tensiometers at the beginning of the growing season, shortly after bud break, but before the beginning of your irrigation season. I recommend putting them in the ground sometime in early May after you are done with your planting operations and first pesticide applications. Information on how to install, maintain and service tensiometers will be provided by the vendor, but are also contained in MSU Extension bulletin E2977 “Using Tensiometers for Scheduling Irrigation of Fraser fir in Christmas Tree Production” available at the MSU Extension Bulletin office, (517)353-6740 or your local county Extension office.

Tensiometers have a vacuum gauge graduated from 0 to 93cb. The higher the reading, the drier the soil, and the harder your trees are working to absorb water. Readings of 10 or below correspond to saturated conditions, readings of 12 to 15cb indicate field capacity, and we recommend starting your irrigation when your readings reach 25 to 30cb depending on your soil type. Good irrigation scheduling starts with good record keeping. Each irrigator should create a record book for tensiometers and record the tensiometer reading every day. The reading should be performed at the same time of the day if possible.

Tools like tensiometers can help you optimize your water usage, improve your irrigation decisions and help you maintain good records and history of the soil water in your site (meeting water use reporting requirements.)
For more information, contact Dr. Pascal Nzokou, email: nzokoupa@msu.edu


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