No one has come up with research stating exactly how much to use. According to the University of Illinois: "Used coffee grounds are considered organic matter, and can be used as a soil additive if rinsed thoroughly." Coffee shops have publicized the use of coffee grounds in the garden. Sprinkling grounds over the soil is fine, to maximize the soil benefit work them into the soil. The best way to use the coffee grounds would be to compost them with other items and use the finished product in the garden. If too thick a layer is used it can become moldy and compact the soil. Here is an anecdotal column on coffee grounds: http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=12978

Hello and thank you for your response.  I was not planning to cover my garden with coffee grounds but coffee bean chaff.  Chaff is a fluffy byproduct of roasting the beans.  It is quite light weight and I don't believe it would compact the soil.  

Thanks for the correction. That should not be a problem. But won't it blow away? FYI: http://www.startribune.com/making-a-good-cup-of-joe-plus-fertilizer-and-soap-from-a-coffee-bean/288870211/ It is on the market as a soil additive so it should be fine as a mulch. You might check with Gardens of Eagan in Northfield. Although they used it as fertilizer incorporated into soil rather than mulch. My search of .edu sites found no research that tested using coffee chaff as mulch. I also didn't find any problems associated with its use in the popular websites. It should work fine as a soil additive in the spring.

Yes this is very helpful .  I'm going to try it and let you know what happens! It might blow away.  That i's definitely a main concern, maybe if I get it wet at first... hmm.  Let's see what happens.  Thank you so much for your assistance.  

Good luck!