Can rats contaminate soil?

[HollyBerryz]

I have a small flowerbed about 1.5 metres long. In one half things grow well. In the other they die. Every time. I can't work this out at all. Anyway we recently had rats in the cavity wall and a cctv drain survey has revealed an unused pipe in the same area which is how think the rats are getting in. It's in the same area nothing will grow. Could it be related?

What was that pipe used for, might give a clue? I can't think what the rats could do to stop the soil being fertile (unless there are a lot of rats peeing on a small are maybe), is something digging things up? Is that area more shady or very hot? Did the builder dump a load of sub-soil or building rubble in that area? Could be a lot of things, check the ph, and get some good topsoil to dress it with.