Active-Optical Reflectance Sensing Evaluated for Red and Red-Edge Waveband Sensitivity
Uncertainty exists with corn (Zea mays L.) N management due to year-to-year variation in crop N need, soil N supply, and N loss from leaching, volatilization, and denitrification. Active-optical reflectance sensing (AORS) has proven effective in some fields for generating N fertilizer recommendations that improve N use efficiency. However, various sensors utilize different wavebands of light to calculate N fertilizer recommendations making it difficult to know which waveband is most sensitive to plant health. The objective of this research was to evaluate across the US Midwest Corn Belt the performance and sensitivity of the red (R) and red-edge (RE) wavebands. Forty-nine N response trials were conducted across eight states and three growing seasons. Reflectance measurements were collected and topdress N rates (40 to 240 lbs N ac-1 on 40 lbs ac-1 increments) applied at approximately V9 corn development stage. Both R and RE wavebands were compared to the at-planting N fertilizer rate, V5 soil nitrate-N, and end-of-season calculated relative yield. In every comparison the RE waveband demonstrated higher coefficient of determination values over the R waveband. These findings suggest the RE waveband is most sensitive to variations in N management and would work best for in-season AORS management over a geographically-diverse soil and weather region.
This proceeding was published as Bean, G.M., N.R. Kitchen, J.J. Camberato, P.R. Carter, R.B. Ferguson, F.G. Fernandez, D.W. Franzen, C.A.M. Laboski, E.D. Nafziger, J.E. Sawyer, P.C. Scharf, J.S. Schepers, and J. Shanahan. 2017. Active-optical reflectance sensing evaluated for red and red-edge waveband sensitivity. p. 121-131. In Proc. Forty-Seventh North Central Extension-Industry Soil Fertility Conf., Des Moines, IA. 15-16 Nov. 2017.