what is the white powdery/dirt like substance on my garden rows?

[JamesHowlett]

of course im a gardening noob ... so my guess is that its some sort of fungus and i may be watering too much ... for a mental image it looks like someone sprinkled flour on my garden watered it and its like this dry coating .... what do i do ... is my garden screwed HALP!!!

 

[gv_girl]

Is it on the soil or on the plants. If it is on the plants it could be powdery mildew.