This season we have been called out on several occasions to consult with facilities and grounds directors that are experiencing poor growth rates with their turf. Due to the steady rainfall we have been experiencing in the Northeast this season the problem has been inevitably associated with soil compaction.
Good soil structure is critical to plant health. Good soil structure allows air and water to move through the soil’s pore space and provide channels for the roots to grow through. Ideally soil pore space would be 25% each for air and water. As soils become waterlogged the 25% of air space is taken up by water. Another way to look at it the soil bulk density increases in wet weather limiting root growth. If there is traffic on the field additional compaction will occur.
According to studies published in the Journal of Experimental Botany report that when plants encounter compacted soil, stomatal closure occurs and shoot growth slows. Ethylene is believed to play a central signaling role during the response of plants to waterlogging. In simpler terms the plant begins to shutdown, its ability to carry on photosynthesis slows, shoot growth and root growth slow. The turf grass will exhibit chlorosis or yellowing under such conditions.
Unfortunately it is difficult to correct poor drainage issues once a field has been constructed. The fields that we have been on this season that were problematic were constructed without crowning (center of the field one to two feet higher than the sidelines) to allow water to flow off the fields. During construction heavy earthmovers were used leading to further compaction of the underlying soil. Over this compacted soil; sod was rolled out. It is very difficult to correct these situations once they have been put in place.
So what to do about it?
Weather - First, we can hope for drier weather.
Limit Traffic - It is important to limit traffic, especially wheeled traffic which will only increase the level of compaction. This means mowers too.
Aerate - Core aeration will help once the fields have adequately dried, though it is important to core aerate only if the grass can actively grow.
Top-Dress - Top-dressing with high quality compost can also help. It is important not to top-dress these native soil fields with sand. While for many it seems counterintuitive, the small amount of sand that you add will only increase the likelihood of further compaction.
Irrigation – While it should go without saying the irrigation system should be turned off; we still need to say it.
Earthworms – It may be a stretch, but earthworms can be introduced for very little money. While conditions may not be ideal for the earthworm, if they take you are introducing natural aerators to the soil.
Be Patient – The grass is not going to grow until it is ready. The introduction of a synthetic fertilizer with high water soluble nitrogen will only make matters worse.