Maintaining soil moisture levels throughout the growing season in Fraser fir plantations

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.  

Most areas of Michigan have just gone through the first extended period of dry and hot weather for the 2007 growing season. At our two irrigation research sites (Montcalm and Jackson counties), no rainfall was recorded from June 6 to June 20. During that period, tensiometer readings (soil moisture potential) measured at 12 inches, increasing from 10 to 20 centibars in non-irrigated plots. (Around 20 centibars, growers should be thinking about turning on their irrigation system.) We also monitored the gravimetric soil moisture (total soil moisture content) at the Jackson farm, and it decreased from 13 to 6 percent at 10 cm below the surface. Note that on sandy soils, 5 percent soil moisture could result in permanent wilting in just a few days depending on plant rooting and condition. (view photo)  We haven’t observed any significant plant mortality; however signs of wilting were present especially in sites transplanted this year. Keep in mind that maintaining good soil moisture is essential for maintaining good health and enhancing all the physiological functions of your trees.

If you have access to irrigation, we recommend putting at least 0.5 inch of water per week on transplant and younger trees, especially in sandy soil if there has been no rainfall, and none is forecasted for the week. Don’t forget to factor in the time you need to run your system through all your irrigation zones before it is too late for the areas you reach last. You should irrigate early in your first zones to be just on-time when you get to the last block.

For more information on using tensiometers to help determine soil moisture, see MSU Extension bulletin E2977 Using Tensiometers for scheduling Irrigation of Fraser fir in Christmas Tree Production. To order this publication, please visit http://www.emdc.msue.msu.edu/intro.cfm or call 517-353-6740.

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