What's alluvial, fecund, rolling, loam,sterile, in the sentences?
The West had plenty of attractions: the alluvial river bottoms, the fecund soils of the rolling forest lands, the black loams of the prairies were tempting to New England farmers working their rocky, sterile land and to southeastern farmers plagued with soil depletion and erosion

This is really a long, difficult sentences.

Question

What's alluvial, fecund, rolling, loam,sterile, in the sentences?
The West had plenty of attractions: the alluvial river bottoms, the fecund soils of the rolling forest lands, the black loams of the prairies were tempting to New England farmers working their rocky, sterile land and to southeastern farmers plagued with soil depletion and erosion

This is really a long, difficult sentences.

Answer

Sentences at the end should be singular: sentence.

Answer

Alluvial : Rocks/stones/sand deposited by a river.
Fecund : Fertile. Good at growing ( plants in this case). It is an old-fashioned, poetic word. 
Rolling : Gentle hills and valleys. Not flat, but not steep.
Loam : A specific type of soil (dirt) which is usually very fertile : http://en.wikipedia.org/wiki/Loam
Sterile : Infertile. In biology and surgery you sterilise equipment with heat/chemicals/radiation to kill all bugs and germs. In this case it is an exaggeration, meaning that the land grows no plants at all.