Sentence:  Mr. Clark still has to <WSD>use</WSD> rotenone with potatoes grown on the least fertile fields , but he has watched the insect damage decrease steadily and hopes that continued use of compost and leaf mulch will allow him to do without it in the future . 
Meaning of the word marked with <WSD> tags:  put into service; make work or employ for a particular purpose or for its inherent or natural purpose