Dear Mary:

Thank you for your question, which has been routed to CSU Extension. Yes, you can use all of the items you mentioned to enrich your soil! The order is not important, but mulch is used as a top dressing. A few things to keep in mind: 1) what soil are you starting with? 2) what is the purpose of your garden plot (growing vegetables)? and 3) is this a raised bed? If you are working with a raised vegetable or flower bed, then filling  the enclosure with a bagged garden soil like MiracleGro, mixing your worm castings into the top 4-6 inches of soil, and adding the mulch on top (after planting) should give you a suitable vegetable or flower garden site. Try to avoid significant concentrations of worm castings touching your plants, as the castings can contain significant salt concentrations. If you are not working with a raised bed, you can always add the items you mention; but the best place to start will be with a soil test to define your soil's starting point and direct your amendments. One testing resource is the CSU Spur Lab in Denver (instructions at https://agsci.colostate.edu/soiltestinglab). For more information on soil amendments and  vegetable gardening specifically (if that is pertinent to you), please see the attachments: "Choosing a Soil Amendment" and "Vegetable Gardens--Soil Management and Fertilization." 

If you have any additional questions, please feel free to contact us directly at <personal data hidden> or<personal data hidden>.

Happy gardening,

Heidi V. 

Colorado Master Gardener Volunteer