In Nelly's defense and a BIG lesson has been learned here for anyone who came from the towns to live in the countryside, "If you have a problem with a farmer the first course of action would be to try talking to him to sort your problem and if this fails try again", believe me you will not want them as an enemy. Fight back you are lucky to have such a nice considerate neighbor. He could have tipped dung in that field for a few year to let it rot, he could tip a load of beet or a rick of straw and then you would see how rats can breed, and he can spread slurry or blood every Friday evening at times in the year and he can fill that field with waining lambs or he could do all his work there at 6 in the morn.