From Longman Dictionary of Contemporary Englishtopsoiltop‧soil /ˈtɒpsɔɪl $ ˈtɑːp-/ noun [uncountable] TASthe upper level of soil in which most plants have their roots
Examples from the Corpus
topsoil• The rich and deep topsoil that lured the first settlers to Deerfield still nourishes the agricultural efforts of their descendants.• Where a lawn is involved, cut away the turf and loose topsoil.• Far over to side, dig some more topsoil, pile on top road, high, high.• How far from the roadbed would we have to go for our topsoil?• In the bulldozed plots they were lowest of all, because the topsoil had been removed.• Where glaciers have scraped it off or rain has eroded it, the topsoil is thin.• In some places the topsoil had been eroded and we had to zigzag up on loose scree.• In any case, the continuation of the war was forcing the revolution to dig much deeper than the topsoil of reforms. 