REMOVE

1. plants
2. soil
3. horizon line
4. horses (animals)

WHAT

1. Visual Works (hierarchy n … (1)
2. exterior views (1)
3. farming (1)
4. fields (land) (1)
5. hay (material) (1)

More 

WHERE

1. Alberta, Canada (1)

WHO

1. Clyfford Still; Still, Cl … (1)
2. Still, Clyfford (1)

WHEN

1. 1920 (1)
2. 1945 (1)
3. between c. 1929 and c. 19 … (1)