My garden has a problem with crops of white patches. They are on the surface of the soil, especially in areas shaded by other plants. I don't see these plaques on the plants. What is this?
That depends. What kind of soil do you have?
What is the level of organic matter in that soil?
Were synthetic fertilizers applied?
How wet is the soil?
Soil is in a mature hardwood forest, first tilled early last spring. It naturally has lots of organic matter (virgin woodland), some sand (coastal flood plain), and enough clay to form a loose clod in your hand.
I don't know how to quantify the organic matter, but there are lots of earthworms and bugs. I added some chicken manure last spring. I occasionally water with miracle grow. The soil is wet after it rains or I water, but we've been in a drought down here, and I water every other day. I don't think it's too wet. Before I water, it actually is very dry.
You probably have a fungus growing on the decomposing organic matter in your soil. I think this is where kimmsr was going with those questions. If there is a lot of organic matter, if it is fresh, and moisture is sufficient, the fungus can appear on the soil surface. It is harmless -- does not cause disease, and beneficial in that it helps break down organic matter into nutrients that the plant can use.
Sometimes when a synthetic fertilizer is used a whiteish crust will form on the soil as the salts from those fertilizers are washed out of the soil. Most often I se that happen in soils that do not drain well.
Sometimes, if the soil has a lot of organic matter, a fungus can form that looks an awful lot like a dog came by an vomited which is why that fungus is called "Dog Vomit Fungus".
I think it is salts if you are on clay soil, and I think I got a bit of that DVF fungus. Is that an edible mushroom?