Did the landlord OK the spreading of the mud?  If not you may have some recourse. 

I've done quite a bit of land reclamation in the past, often dealing with mud pits.  About the only way I've been able to fix them to anything near what they were prior was to 'farm' the mud out over several acres real thin.  Like a tenth or so.  But keep in mind these were heavy clay soils with high CEC's that can 'eat up' a lot of things. 

I can only think of one time I saw drilling mud do a pasture some good.  This land was junk when they started so anything was an improvement.  I was wet, sandy, low pH and would barely grow weeds, afterward it actually had some grass.  Not sure if it was maybe just because it made a 'hill' out of a swamp, or what.