Here are a few tips for combining your keywords into powerful searches:

Put quotation marks around a phrase

"flowering plants"

Without the quotation marks you could get an article that mentions plants but not flowering plants specifically.

Use an asterisk * after the word stem

angiosperm*

This returns articles that mention angiosperms as well as articles that mention Angiospermae.

Combine synonyms with OR

"flowering plants" OR angiosperm*

Look for a + sign button to add more topics to your search

If you want both topics included in your search, make sure select the AND operator to connect them.

Use parentheses and AND to combine topics in a single search bar

("flowering plants" OR angiosperm*) AND soil