When this poem was first published in 1946 it was entitled "Dark haired Myriam ran away".I'd say therefore, like others above that the poem is about the poet's ill-fated love for a local girl. The "still making hay" reference is clearly a reference to Kavanagh's own country roots.
Kavanagh lived in Pembroke St., Dublin, close to Raglan Road, from 1946 (the date of the poem) until 1958 and then at 19 Raglan Road itself from 1958 to 1959.
Peace
mcmoo