Dear Jackie: Here is a URL to the poems, and a discussion of the whole matter.

http://www.oneworld.org/tlio/history/clare.html

It is about the enclosures in the seventeen hundreds, and the peasants' revolt. Captain Swing was apparently nom de guerre of one of the peasants. Hay ricks are hay simply piled as high as possible in the field, with little protection from the rain and spoilage. Hay baling is a really recent technology.