He hypothosized that too much organic accumulation or rapid death of surface roots could result in reduced infiltration, a higher water content, and a decrease in both the total oxygen within this zone and movement of oxygen within this zone.
In addition, when OM >4.5% by weight, macroporosity declined substantially and it was more likely that a massive root dieback from hot, humid weather would occur. Surprisingly, prolific root growth during periods of optimum temperatures (soil 55-65ºF, air 60-75ºF) also plugged macropores and reduced oxygen levels.
In summary, OM dynamics were thought to be influenced by:
* Grass type & density
* Anaerobic conditions (oxygen within 0-2 inches) caused by too-frequent irrigation
* Acidic conditions in the top 1-inch possibly caused by acidic nitrogen fertilizers
* Limited root depth because OM has reduced oxygen diffusion
* Root & crown injury
* Inhibition of nutrient & water uptake
Preventing &/or curing this OM accumulatiom problem is achieved by surface management (verticutting, scarification), and regular aeration and topdressing. Keeping the top 0-2 inches of playing surface free-draining and with adequate levels of oxygen appears to be the key to surviving summer stress.
Authors: Dr. Karl Danneberger
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