|Cipra, Jan - COLORADO STATE UNIVERSITY|
Submitted to: Biosystems Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 12, 2008
Publication Date: November 10, 2008
Citation: Bausch, W.C., Halvorson, A.D., Cipra, J. 2008. QuickBird Satellite and Ground-based Multispectral Data Correlations with Agronomic Parameters of Irrigated Maize Grown in Small Plots. Biosystems Engineering 101 (2008), pp. 306-315 DOI information: 10.1016/j.biosystemseng.2008.09.011 Interpretive Summary: Agronomic research is typically conducted in small plots to minimize variability and to have control over the parameter(s) being investigated. Remote sensing techniques provide nondestructive, quantitative information about various plant parameters from spectral variables (individual wavebands and vegetation indices). Thus, small plot research and remote sensing research compliment each other. Unfortunately, satellite images of small plot crop research are not practical due to spatial resolution issues. The QuickBird satellite launched by DigitalGlobe in 2001 has potential for estimating agronomic parameters of crops grown in small plots. Research was conducted to investigate that potential. Images were acquired at the tassel growth stage of corn in 2002 and 2003. Results from the study showed that plots 10.7 m by 21.6 m (smallest plot area in the study) were of sufficient size for accurate location on a QuickBird image and contained sufficient pure pixels within the plot boundaries for crop monitoring. Correlations of a normalized chlorophyll index calculated from QuickBird digital counts and ground-based reflectance values versus plant nitrogen content were not significantly different. Consequently, QuickBird satellite imagery appears to be a useable source for spectral measurements of small plot (with limitations) crop research which may replace and certainly compliment aerial photography and ground based sensors. Further research with more crop growth stages and crops would be desirable.
Technical Abstract: Satellite remote sensing has not been practical for agronomic research conducted in small plots due to spatial resolution issues. Objectives were to determine (1) the potential use of QuickBird high resolution digital images for estimating agronomic parameters of irrigated maize (Zea mays L.) grown in research size plots and (2) if digital number (DN) values were adequate for assessing these agronomic parameters. Conventionally-tilled plots varying in size from 21.3 m x 21.6 m to 10.7 m x 21.6 m were used. QuickBird imagery was obtained at the tassel growth stage for two growing seasons along with ground-based reflectance. Relative green (G) waveband DN was highly correlated with available nitrogen (N) at planting and relative values of grain yield and total biomass. Relative spectral indices containing G and near-infrared (NIR) wavebands, i.e., the GNDVI, the NIR/G ratio and the chlorophyll index ((NIR/G) – 1) produced good correlations. Regression curves of the normalized (NIR/G) - 1 index calculated from ground-based reflectance and satellite DN values versus leaf N content were not significantly different (' = 0.01). Results indicate that QuickBird images show promise for estimating agronomic parameters from small plot research. Additional research is required to expand the results to more crop growth stages and crops.