An apparatus is described for assessing plant status using biophysical and
biochemical properties of the plant remotely sensed by the invention
thereby allowing selective monitoring, elimination or treatment of
individual plants. In a preferred embodiment, a single polychromatic
emitter provides coincident light beams; one beam substantially in the
visible portion of the spectrum (400 nm to 700 nm) and the other in the
near infrared (NIR) portion of the spectrum (700 nm to 1100 nm). This
light beam illuminates a small surface area on the ground, which may be
bare ground, desired plants or undesired weeds. The beam of light may be
focused, collimated or non-focused. A detector array, usually composed of
a visible detector and a NIR detector, detects portions of this
polychromatic light beam reflected by the surface area and provides a
signal indicative of whether the detected light was reflected by a plant
or by some non-plant object such as soil. A controller analyzes this
signal and, assuming a plant is detected, responds by activating a device
to take some action with respect to the plant or stores the analyzed
signal with corresponding DGPS position in the controller's memory for
later analysis. A number of actions may be taken by the controller. For
instance, if the plant is a weed, the desired action might be to spray
herbicide on the weed. Or, if the plant is a crop that is determined to
be lacking in nutrient, the desired action may be to apply fertilizer.
Additionally, if the plant under test is a turf landscape, such as found
on golf courses and sporting fields, plant biomass may be mapped and
geo-located using GPS for later, comparative analysis.