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Does mowing temporarily reduce my lawn's evapotranspiration rate? #581190

Asked July 18, 2019, 12:55 AM EDT

Hi!

Would you happen to know the transpiration of my lawn is reduced after a I mow it? The lawn grass is around 6 inches high when I mow it and 3 inches after mowing. I found an old article in the Agronomy Journal from 1981 that shows evidence of a 13% ET reduction for every few centimeters of height. I realize that mowing can increase evaporation due to increased surface exposure, and that mowing can discourage the growth of roots necessary for drought-tolerance. But assuming a healthy lawn oscillating between 3 inches and 6 inches during a 2-week mowing cycle, is it safe to conclude that ET is reduced as a function of loss of leaf surface stomata?

Much thanks for your expert opinion,

Regards,
Simon Hill

Denver County Colorado

Expert Response

Hi Simon,

Taller grass does encourage root growth, but we recommend mowing to 3 inches, which you are doing. 3 inches is tall enough to continue to encourage the root growth that keeps grass healthier.

We recommend never removing more than 30% of grass height in a single mowing, however. You may consider increasing your mowing frequency so you are not removing as much of the blade at one time.

The reduction in transpiration is not a concern, since you are maintaining tall grass blades. Watering deeply and less frequently also encourages deep root growth. During these hot, dry weeks we've been having, water 2" a week.

Colorado Master Gardener, Denver County Replied July 20, 2019, 5:24 PM EDT
Thank you!
The Question Asker Replied July 21, 2019, 9:30 PM EDT

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