My garden soil needs a little help.  Yields were low last year.  I want to add some compost.  How much compost should I add?  Is 2" or 3" too much?  I will be growing mostly tomatoes.   Is mushroom compost the good stuff?

Compost is always a pretty safe bet, but you may want to consider a soil test just to see where you stand and make sure you're not missing some critical nutrient or have a wacky pH or something.  2-3" is not too much, but it wouldn't hurt to incorporate it into the soil if possible instead of just dumping it on top.

Never used it myself, but mushroom compost is supposed to be good stuff. I wouldn't hesitate in using it.  Again, though, you may want to at least check the pH of your soil... the soil can be chock full of delicious nutrients, but if the pH is off too far the plants can't get to them.  Most garden stuff (excluding acid-loving blueberries and such) want a pH between 6 and 7.

Compost is great and it's generally hard to add too much.

That said, many composts have a lot of shall we say, city sewer solids as a major component. If composted correctly, they are fine but can have a bit of salts. As long as your ground is pretty loamy, the salts won't accumulate with proper watering.

Also, if you use a lot of compost year after year, watch the potassium levels as they tend to climb and can become toxic to plants. It's wise to test with a home kit as a minimum. It's cheap and easy to do.

Thanks guys.