Answer: If the hydrated manure is not an overly "hot" product or excessively high in nitrogen, it should work well in small amounts. Unfortunately I am not familiar with the specific product to which you referred. If it is sold as a bagged product it may have instructions as to how to use it on the label. In general it is fine to add a top dressing of compost and/or well aged and rotted manure under the mulch.
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