Root Depth, Crop Coefficient

I have new Marathon II sod that has been installed for about 8 weeks now. As a cool season grass, the default root depth is about 6 inches,(clay loam soil) but does it make sense for me to keep that at say 3 inches for now, and increase it up to the 6 inches by the end of the growing season?

In another zone I have periwinkle planted on a medium slope. What zone type should I use for this? In looking at the Advanced Settings, it looks like “Zone Type” only affects root depth and crop coefficient. So I guess it does not matter so much as long as these values are in the correct range.

Roots for periwinkle (vinca minor) stay fairly shallow, according to one online source, so I am thinking no more than 3 or 4 inches.

What is crop coeffecient?

That sounds reasonable to me.

Shrubs? or Perennials? You can then drop the root zone depth if you want.

This is the difference in ET between the crop and reference evapotranspiration (ET). If reference ET is for the day is .2 inches, and crop coefficient is 80%, that means the plant burned .16 inches. I tend to think about it as how efficient the plant is able to hold onto moisture. The higher the crop coefficient value (%), the faster the plant is burning off moisture and will need to be watered more frequently.