I had been asked this question during an interview.
The doubt is from Disposal of Effluent in portion Effluent Treatment of Bioprocess Engineering
For explanation I would say: Achieving good agitation is an important part of this. Failure to properly agitate the manure will result in a continuous buildup of settled solids within the storage, resulting in less and less available storage as time goes by. Good agitation of the manure will re-suspend those settled solids and facilitate their removal from the storage ensuring we maintain that capacity we need. Additionally, agitation of the manure helps homogenize it and provide a more consistent nutrient content as it is applied.