Growings On: Persistent dry weather can impact lawns, crops

Roger Gates

Pam Knox, agricultural climatologist and director of the University of Georgia Weather Network, recently commented on the likelihood of continued dry weather. Knox concluded from the latest National Weather Service seven-day Quantitative Precipitation Forecast map that Georgia is “unlikely to see any rain at all for at least the next week.”

“This is bad, because, coupled with the well-above-normal temperatures, moisture stress is going to cause problems for ripening crops and will make it hard to start fall crops," Knox said. "Warmer than normal temperatures and dry conditions are expected to continue into October, so don’t expect relief any time soon.”

Reviewing the latest monthly and seasonal outlooks released earlier this week by the National Oceanic and Atmospheric Administration Climate Prediction Center, Knox suggested “they lean towards warmer than normal temperatures for both October and the October-December period across the region.” Knox further commented that the Climate Prediction Center “indicates that current areas of drought are likely to continue and could expand. Not a big surprise considering how dry we have been and are predicted to continue to be, as well as experiencing temperatures 15 to 20 degrees above normal after our brief respite this past week.

Sept. 23 marked this year’s autumnal equinox, when day and night are both about 12 hours long. Decreasing daylength is a signal that some perennial plants respond to with dormancy, an adaptation to persist through the winter. Onset of dormancy can be modified by other climatic conditions, such as moisture stress.

Lawn grasses in particular, may be affected by dry conditions occurring during the fall. During the fall transition into dormancy, insufficient production and storage of plant nutrients derived from photosynthesis can translate to issues during spring green-up.

Clint Waltz, UGA Extension turfgrass specialist, suggests these tips for managing turfgrass as it transitions into dormancy:

• Turfgrass stress can be reduced by using a sharp mower blade and raising the cutting height by half an inch or to the tallest allowable height of the recommended mowing range during drought. A clean cut also reduces moisture loss through wounds and minimizes entry points for disease. Taller shoots promote deeper roots and a dense canopy can help to reduce ground surface temperatures and conserve moisture. Grasscycling (mulching clippings versus bagging) can also help to conserve moisture.

As grasses move into dormancy they need to “harden-off." Nitrogen fertilization encourages new shoot growth which directs plant sugars, and other metabolites, away from storage organs (for example, rhizomes, stolons and crowns). These storage organs and sugars provide the energy for the grass to green-up next spring. By allowing the plant to harden-off and accumulate sugars in the storage structures, the grass is better able to survive winter stresses and recover next year.

Many herbicides act upon plant growth processes and can be less effective during periods of drought when weeds are not actively growing. In addition, certain herbicides may cause damage to drought-stressed turf or non-target landscape plants due to volatilization and drift during high temperatures. Review your pesticide labels for specific information regarding temperature requirements, watering requirements and proper application.

The optimum watering schedule can be roughly determined by observing the number of days that pass between signs of moisture stress. Apply sufficient water to saturate the root zone to a depth of 6 to 8 inches. Clay soils and sloped areas may require staggered watering intervals to allow time for water infiltration between cycles and prevent runoff. Irrigating in early morning conserves water by reducing evaporation and drift. A good practice is to align watering schedules with drought management rules so that in the event of a declared drought, the appropriate watering program is already in place. The 2010 Water Stewardship Act permits lawn watering between the hours of 4 p.m. and 10 a.m.

It may be premature to anticipate the pleasant sensations we associate with the first spring flowers and the aroma of newly mown lawns, but careful management of turfgrass this fall will promote successful lawn recovery next spring and increase the probability that the aromas you appreciate next year will be from desirable lawn grasses and not weeds that exploited turf plants weakened the previous fall.

Roger Gates is the agricultural and natural resources agent for University of Georgia Extension, Whitfield County. Contact him at roger.gates@uga.edu.

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