Thursday, April 25, 2013

Spring Flooding of Turf

Dr. Kevin W. Frank
Assoc. Professor & Extension Turf Specialist

In the last week heavy rains blanketed most of the state resulting in streams and rivers overflowing their banks and many low lying areas flooding.  The water has slowly started to subside and turf that was flooded may be exhibiting damage symptoms.  Factors that determine turf survival under water include: turfgrass species, submergence duration, submergence depth, water temperature, and light intensity. 

Turfgrass species differ in their ability to survive flooding.  Unfortunately there are no hard fast numbers such as Kentucky bluegrass will survive 5 days and creeping bentgrass 15 days under water.  Instead species have been assigned relative submersion tolerance ratings: creeping bentgrass – excellent, Kentucky bluegrass – medium, Poa annua and perennial ryegrass – fair.  As submergence depth increases the potential for injury increases.  If the leaf tissue is above the water line – even just a little bit – the turf will probably survive.  On golf courses many have observed creeping bentgrass floating on the edge and even growing out into a lake.  This is a perfect example of turf surviving when partially submerged.  The final two factors affecting turf survival are water temperature and light intensity.  Both of these factors are working in our favor right now as the air and water temperatures have been cool.  Flooding during the summer months when temperatures are higher often result in damage to the turf when it’s submerged for even a short time. 

Many golf courses in flood plains have flooded.
As the water recedes, the turf may be yellow or brown.  The discoloration is related to the turf losing its ability to take up nutrients.  It doesn’t take long once turf is submerged for soil oxygen levels to decline and root hairs to begin to die.  As the root system becomes impaired, nutrient extraction and water uptake will be limited.  Keep this in mind once the water has receded as the turf may benefit from a light fertilizer application.  To assess if submersion has caused injury, extract several plants from the flooded site and cut a horizontal cross section through the crown.  If the crown is white and firm – it has survived.  If the crown is brown and mushy – it’s dead, so time to develop a reestablishment plan.  Finally, for those areas that were flooded due to a stream or river overflowing a bank you are probably dealing with silt or soil deposition.  Removal of soil deposition can be difficult and seeding into the deposited soil can be an option.  Once successfully reestablished soil cultivation such as core aeration or slicing will benefit the turf by breaking through deposited soil layers to facilitate rooting and water infiltration.

Yellowing of turf from flooding.

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