There may be some legal issues with altering field tile flow, let alone the closer-to-home effects of good neighbor policies. The ramifications of plugging up an operative field tile should be carefully considered.
Field tile input is usually a mixed blessing. Good, because it it will provide a valuable water source. Bad, because it is usually run-off from a farm field that may be rich in chemical nutrients. Being a plastic tile indicates that the inflow end will likely be some type of hickenbottom that will allow silt to freely flow in, also. A number of us have field tile in-flows. My drain tile story
is posted on this thread. 
