Most of the area's alluvial soils (soils deposited by river flooding) certainly had a mixed history of cultivation and abandonment cycles.
(soils; deposited; by river flooding) (Most of the area's alluvial soils; certainly had; a mixed history of cultivation and abandonment cycles)
soils Most of the area's alluvial soils
deposited certainly had
by river flooding
a mixed history of cultivation and abandonment cycles