When I go up through the mowing field,
The headless aftermath,
Smooth-laid like thatch with the heavy dew,
Half closes the garden path.
And when I come to the garden ground,
The  “Mowing Field”  could possibly be a metaphor for the World. The Earth. 
 The headless aftermath can mean that he Robert never thought that the way the World worked would ever be realistic. The horrible things in Life was not imaginable for Robert.
A Late Walk