Why Grass Died instead of going dormant for 2010

Here is some good research done by Eric Bickel the Hallbrook Golf course Superintendant.  These factors show why this has been the worst year in the last 20.

KC Weather Factor, 2010

By Eric Bickel


Extreme heat and humidity have persisted for over four weeks.  The wet conditions this spring coupled with the heat stress have combined for peak turf loss conditions.  The cold spring and wet conditions (33” April through July) was not conducive to healthy deep root development.   The cool season grasses have been surviving for the last six weeks off reserves in the root systems.  Those reserves and the root systems have all but run out.  In addition, high humidity has created constant high fungal disease pressure.

Dew points, temperatures, wind speed, and soil temperature are the key climactic factors which measure the stress associated with cool season grasses ability to perform its basic physiological functions, (respiration, photosynthesis, evapotranspiration).  A brief summary of these factors, their critical values, and their occurrence follows for the period of June through Aug 11th.


Days with highs of 90 or above                                                        37

Days with a low temperature above 70                                           43

Days with a average dew point above 70                                        46

Days with an average wind speed of 10 mph or less                      65

Days in which soil temperatures have been above 86                    52


When all five of these factors occur simultaneously at their critical values (highs & lows above 90 & 70 respectively, dew points above 70, soil temps above 86, and wind speed below 10), cool season grasses are in a state of full blown decline.  There is no recover for that day.  The plant can no longer perform its basic functions normally.  Metabolic activity is sustained solely at the expense of the root system.  When this occurs for extended periods of time little can be done to alleviate the issue.


Total days in which all five of these factors occurred simultaneously over the last 20 years, (i.e.# of severe root decline days)


Year                90’       91’       92’       93’       94’       95’       96’       97’       98’       99’

# of days          5          8          1          3          2          14        5          10        12        17*


Year                00’       01’       02’       03’       04’       05’       06’       07’       08’       09’      

# of days          9         16        13        9          5          7          11        8          5          6     


*1999 had the most consecutive days with 13


In 2010 this has happened 29 days, (this could hit 32 on Saturday, August 14th!)