We used to have sludge applied every year. Only for non-food crops though so if you intended to sell the stuff for milling or malting you couldn't apply it that year.
The material in the UK is called dewatered sewage cake. It looks black and is lime stabilised, its the solids left after everything has been passed through a sewage plant. It isn't untreated waste, that is no illegal to use on farmland.
Water companies basically pay you to take it as it is cheaper than landfilling or dumping the material at sea. It is spread at a low rate using big spreaders, and then cultivated or ploughed in immediately afterwards.
Certainly the sewage contains a lot of Phopshate (from washing detergents) and Potash, not alot of nitrogen, and it is an excellent source of nutrients. We usually applied it to land that would be drilled with canola/oilseed rape shortly afterwards. It is a good product though one must be careful of its heavy metal content and so the water company supplying the material would do soil tests to make sure we weren't approaching high levels of heavy metals in our soils.
I have spread many hundreds of tonnes of this stuff myself, I would say it is more pleasant to work with than chicken muck. It mostly smells of washing powder.
The only problem is we needed a hard standing and a large patch of land to store the material all year- the waste companies would haul it in and tip it throughout the year and we would only spread it in the autumn in keeping with our crop rotation. In a wet autumn the spreaders would leave a lot of compaction so it would be best to deep rip or subsoil afterwards, this could be why your neighbours crops are poor.
The material itself is quite heavy and dense, but it is friable and it spreads very well and evenly. Don't let them tip on a slope, as the rain can wash the stuff downhill. Best to tip it in a slight depression or else bank up some soil around the heap, or maybe put bales around it.
