Light intensity in horticulture is commonly measured in which of the following units?

Light intensity in horticulture is typically measured in foot-candles because this unit specifically quantifies the amount of light that falls on a surface area. A foot-candle refers to the illuminance produced by a light source of one candela at a distance of one foot, making it particularly relevant for assessing light levels in agricultural and horticultural environments where plants are grown.

While lux is also a unit of illuminance (with one foot-candle being approximately 10.764 lux), foot-candles are more traditionally used in horticultural practices, especially in North America.

Watts measure energy consumption rather than light intensity and do not provide a direct indication of how much usable light is available for plant photosynthesis. Fahrenheit, on the other hand, is a temperature measurement unit and does not relate to light intensity at all. Hence, foot-candles remains the most suitable and commonly utilized unit for measuring light intensity in horticulture contexts.