FACULTATIVE. An adjective that implies that a state is not obligatory. For example, an organism may be able to live off dead or living material, i.e. a facultative saprophyte.

FALLOWING. A process of leaving an area unplanted for a period of time. Often used to control weeds by allowing them to germinate and then tilling them.

FERTILISER RATIO. The ratio of N-P-K in a fertiliser. For example, a 6-6-6 fertiliser would have a 1:1:1 ratio.

FIELD CAPACITY. The moisture content of a soil after the free water has drained from it.

FILIFORM. Term used to describe a long, slender, grass leaf.

FLORET. In grasses, the flower including the lemma.

FORMULATION. The form in which a pesticide is offered for sale, i.e., dust, granules, wettable powder, and emulsifiable concentrate.

FUMIGANT. A volatile chemical disinfectant which as a gas or vapour kills destructive plants or animals.