EVALUATION OF ACTIVE OPTICAL SENSORS FOR ASSESSMENT OF PLANT N IN IRRIGATED CORN

Authors: Bausch, Walter; Halvorson, Ardell

Submitted to: Proceedings Great Plains Soil Fertility Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/20/2006
Publication Date: 3/7/2006
Citation: Bausch, W.C., Halvorson, A.D. 2006. Evaluation of active optical sensors for assessment of plant n in irrigated corn. Proceedings Great Plains Soil Fertility Conference. 11:149-154

Interpretive Summary: Nitrogen (N) fertilizer is a vital nutrient for all plant growth and has received attention for a long time as a potential source of ground water pollution because of its mobility through the soil and because of the large amount of N fertilizer used. New management techniques using remote sensing have been developed to improve N use by crops by detecting the crop’s N status and applying N when the crop needs it and where N is needed in the field. Unfortunately, the remote sensing systems used to develop these techniques require sunlight. A new generation of sensors referred to as active sensors are becoming commercially available. These sensors provide their own illumination such that they can be used anytime of the day under all possible sky conditions to collect data. Unfortunately, these sensors illuminate small areas due to power requirements. Comparison of two of these active sensors to various levels of leaf N content in irrigated corn showed that they responded differently. Thus, additional research is required to fully understand their behavior to a plant’s N status to effectively utilize the sensor for N management.

Technical Abstract: Nitrogen (N) fertilizer has received attention for a long time as a potential source of ground water pollution. Considerable research has been conducted to investigate use of remote sensing for assessing plant N status to improve N use efficiency. Most of these studies have used passive type sensors which require sunlight. Clouds hinder their performance. Active type sensors provide their own illumination which means they can be used to take measurements anytime of day under all possible sky conditions. This study compared two active sensor systems to a passive system and their response to various levels of leaf N content in irrigated corn (Zea mays L.). Results showed that the two active sensors responded differently to corn leaf N content. The active Holland Scientific Crop Circle and the passive Exotech1 data were somewhat similar. Additional research is required to fully understand the active sensor’s behavior to plant N status to effectively utilize the sensor for in-season N management.