Topdressing 101

Many times I receive questions from members on why I topdress so much and what is the purpose.  The individual leaves on a grass plant only live for a short period.  You see in the picture below the lower leaves are brown and getting ready to drop or sluff off the stem and new leaves grow.  Many people think the grass plant maintains the same blades and you just keep cutting them off all summer, but actually new ones grow up and old ones die off.

Individual grass plant

 As these blades die off they add organic matter to the surface of a playing area.  We spread sand on the surface to dilute this accumulation of organic matter.  We try to match the growth of the plants with the quantity of sand applied.  The goal is to create a nice "matt" layer on the surface that is a mixture of sand and organic matter.  If we did not dilute this organic matter with thatch, then it would turn into a sponge layer on the surface. A sponge layer will hold excess water and nutrients, allowing the roots of the plant to stay right in the sponge and not grow down deeper.  When the sponge dries out in mid afternoon then the plants will wilt.  This sponge will create soft bumpy conditions.  Below you see a sample from a green.  A very nice mixture there of sand that keeps the surface on the greens very firm, fast, and smooth.    

Core sample from a putting green

You can also in the greens sample above that the upper 1.5 inches has more sand and more of sand color than the darker material below that.  The lower section would be from turf managers before me and you can see there is more sand in the division I have topdressed.  That would explain why people have said greens are firmer and smoother since I have been here, because of the increased sand topdressing.  The topdressing layer also protects the crown of the plant, which is the main heart of the plant, and it protects it from all the traffic we put on the greens with mowers, rollers, others equipment, and golfers foot prints.

Below is a sample from an approach.  Approaches were not topdressed before I arrived, so in 3 seasons we have built up a nice 1 1/4" sand layer on the approaches.

Topdressing on a soil based approach

Not only does the sand dilute down the organic matter, create firmer and faster conditions, but ti also all ows water to infiltrate into the soil creating less water on the surface which is also going to decrease our disease potential.  The sand layer also decreases worm casts as they do not like to burrow up through the abrasive sand rubbing against their cuticle.