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United States Department of Agriculture

Agricultural Research Service

Title: Evaluation of in-Field Optical Sensor for Nitrogen Assessment of Barley in Two Irrigation Systems

Authors
item Kim, Yunseop
item Evans, Robert
item Waddell, Jed

Submitted to: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE)
Publication Type: Proceedings
Publication Acceptance Date: August 8, 2005
Publication Date: September 25, 2005
Citation: Kim, Y., Evans, R.G., Waddell, J.T. 2005. Evaluation of in-field optical sensor for nitrogen assessment of barley in two irrigation systems. In: 2005 Pacific Northwest Section Meeting, September 22-24, 2005, Lethbridge, Alberta, Canada. Paper Number PNW05-1004. St. Joseph, Mich.: ASAE.

Interpretive Summary: Nitrogen (N) is an essential nutrient for plant growth and one of the leading sources of concern for leaching into groundwater. Development of an N management system potentially allows producers to reach their production goals, while minimizing the effects on the environment. This research evaluates the performance of an optical sensor for real-time assessment of N status of barley crops. The ground-based sensor generates light at two specific wavelengths and measures the light reflected off the plant canopies. Two sensors were mounted on a custom-designed platform: one nadir and the other oblique. The platform is a four-wheeled hand cart with high clearance and equipped with a computer and GPS. The data were registered with GPS coordinates and processed for geospatial mapping. The performance of the sensor was validated under various ambient illumination conditions. Data were collected representing the changes in crop reflectance over several stages of the growing season. The performance of the non-contact sensor in detecting N stress was evaluated on the experimental plots of malt-barley in two different irrigation systems: one sprinkler and the other flood irrigation. Both plots were prepared with five different N treatments. The sensor responses were collected and compared with reference measurements from a SPAD chlorophyll meter and amount of N applied. High correlations were obtained between reflectance responses and reference data on both plots. Small values of standard variations indicated stable performance of in-field sensing system throughout the season. Further analysis to observe the yield effect due to various N applications showed no significant increase over 112 kg/ha.

Technical Abstract: Development of N management system potentially allows producers to reach their production goals with minimum environmental impact. This research evaluates the performance of an optical sensor for real-time assessment of N status of barley crops. The ground-based sensor generates light at two specific wavelengths and measures the light reflected off the plant canopies. Two sensors were mounted on a custom-designed platform with high clearance and equipped with a computer and GPS: one nadir and the other oblique. The data were registered with GPS coordinates and processed for geospatial mapping. The performance of the sensor was validated under various ambient illumination conditions. Standard deviation was less than 0.051 in sensor’s NDVI responses for sunlight illumination effect over 26 hours. Small variations were found under the illumination changes between sunny and cloudy. Data were collected representing the changes in crop reflectance over several stages of the growing season. The performance of the non-contact sensor in detecting N stress was evaluated on the experimental plots of malt-barley in two different irrigation systems: one sprinkler and the other flood irrigation. Both plots were prepared with five different N treatments and four replications. The sensor responses were collected and compared with reference measurements from a SPAD chlorophyll meter and amount of N applied. Correlation coefficients of r = 0.75 and 0.84 were obtained between reflectance responses and reference data on flood and sprinkle plots, respectively. Further analysis to observe the yield effect due to various N applications showed no significant increase over 112 kg/ha.

Last Modified: 12/19/2014
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