Answer: There could be several factors at work here. Bagged soil can be of varying quality and so the fertility or pH could be out of whack, as could be the structure of the soil. You might want to have the soil tested to find out specifically what is missing and then add amendments based on the test results. (Your county extension should be able to help you with the tests and interpreting the results.) In general, it is a good idea to add organic matter (such as compost or old rotted leaves or aged barnyard manure and bedding)to help improve soil structure. You should add more on a regular basis to help feed the soil as it breaks down over time and to keep the soil structure suitable for optimum plant growth. In terms of the mulch, while it is possible that a more woody mulch can temporarily tie up nitrogen in the soil, in this case I would look further than that and focus on the soil itself.
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