Where can I send soil or worm castings for testing for N-P-K levels?
I would like to try straw bale gardening and for the last year have been actively into vermiculture and have worm castings that I would like to have tested to determine their N-P-K levels for both conditioning my straw bales and for making potting soil.
Any help or advice on any of the above would be greatly appreciated!
Vermiculture is a fascinating topic. Here is research-based information for you from Colorado State University (CSU): http://planttalk.colostate.edu/topics/soils-amendments-composting/1622-composting-worm-composting/
You are right! Testing soil before planting is always a good idea. Here is a link to the homepage for Colorado State University’s soil test lab - http://www.soiltestinglab.colostate.edu/.
How can you can most accurately sample your soil? Check out: http://planttalk.colostate.edu/topics/soils-amendments-composting/1606-soil-tests/
Here is more information for you about straw bale gardening: http://msue.anr.msu.edu/news/no_digging_required_straw_bale_gardening
You also asked about making potting soil. Research suggests: Do not use native soil, even if you can pasteurize it. Most native soils have a high percentage of clay particles that easily compact reducing the oxygen that is available to the roots. (Source document: http://extension.colostate.edu/topic-areas/yard-garden/container-gardens-7-238/ )
If you want to see straw bale gardening testing in action, you may want to visit Treasure Island Demonstration Garden in Weld County, Windsor, CO.
Have fun trying straw bale gardening!