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Title: Laboratory evaluation of the GreenSeeker (TM) hand-held optical sensor to variations in orientation and height above canopy

item Martin, Daniel - Dan
item Lopez, Juan De Dios
item Lan, Yubin

Submitted to: International Journal of Agricultural and Biological Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2012
Publication Date: 2/16/2012
Citation: Martin, D.E., Lopez, J., Lan, Y. 2012. Laboratory evaluation of the GreenSeeker (TM) hand-held optical sensor to variations in orientation and height above canopy. International Journal of Agricultural and Biological Engineering. 5(1):43-47.

Interpretive Summary: Precision agriculture offers the potential to target application of nutrient and pesticides to specific areas within fields, but improved approaches are needed to rapidly detect patterns of crop health. Crops reflect various wavelengths of sunlight that can be measured by aircraft or satellite and used to identify patterns of crop health due to nutrients, infections, and pest infestations so that plant growth regulators, pesticides, defoliants, and fertilizers can be applied to specific areas of the field as needed. However, low clouds can prevent aerial imaging of fields. New hand-held or tractor-mounted light reflectance instruments allow farmers and crop consultants to survey crop health over an entire field regardless of cloud cover. A hand-held reflectance instrument was tested for its sensitivity to various operating conditions. The reflectance instrument was significantly sensitive to height and orientation relative to the crop canopy. The results identify proper use of the hand-held instrument to consistently gather high-quality reflectance data that can characterize plant health, which may lead to reduced chemical inputs and increased profits.

Technical Abstract: Handheld optical sensors recently have been introduced to the agricultural market to simplify acquisition of spectral reflectance data. These handheld sensors are able to provide operators with Normalized Difference Vegetative Index (NDVI) data when cloud cover prevents acquisition of satellite or aerial images. This research addressed the sensitivity of the GreenSeeker hand-held optical sensor to changes in orientation and height above a ryegrass canopy. Planter boxes were oriented both parallel and perpendicular to the light beam from the sensor head and heights of 30.5 cm (12”), 61.0 cm (24”), 91.5 cm (36”) were tested. Results indicated that the sensor was significantly sensitive (P<0.0005) to both height above canopy and orientation of the sensor relative to the target. Operators should remain consistent in the use of the sensor and orient the sensor head in-line with the target to obtain maximum signal response.