Question

Infected soil   Dear Sir,
We noticed our lawngrass(kikuyu) started to recede until  at this point few grass is growing and bare patches of soil are getting bigger.  Upon digging up the soil to plant grass seed, we noticed hard clumps of soil, and when broken up, saw it was permeated with white mouldy growth.  Although the lawn was watered the previous night, these clumps seemed to be dry while the rest of the soil is moist.  The white mould is not visible from the surface. Can you please suggest any remedy?

Answer
Hi Jan:
This growth is a type of fungus living on organic material in the soil.  It can be be one of thousands of different kinds.  Virtully impossible to alleviate it by physically removal.  A lab exam would be necessary to determine if it is damaging the lawn or just a normal inhabitant causing no disease.  Most of these soil organisms cause no harm to plants.  They can be a nuisance to the homeowner sometimes by their sudden appearance or sometimes odor.  Physically digging it out of the ground will not guarantee its removal, but may give you some temporary relief.  Thick clumps of the mycelium (tiny threads) of the fungus can sometimes repel water, so you may consider just breaking up those dense areas in the lawn with something like a pitch fork and then watering throughly.  

There are some of these organisms that causes fairy ring in lawns.  One of the ways that they damage the lawn is by making the soil hydrophobic (water repellent).  Trying to remove this stuff by digging out the entire area can be labor intensive and one cannot be sure that they removed all of it, thus it will eventually come back. I'd give the pitch fork a try, followed by deep and through watering if you see areas where the grass may be drying out.

Steve