Using High-Resolution Satellite Imaging to Evaluate Nitrogen Status of Winter Wheat

ABSTRACT

Nitrogen (N) applications often increase crop yields significantly, but N needs vary spatially across fields and landscapes. The color of the wheat plant is sensitive to N status and may provide a means to accurately predict N fertilizer rates matching spatial variability. Previous researches have reported that remote sensing may contribute to N management decisions by collecting spatially dense information. The objective of this study was to determine the feasibility of using high-resolution satellite imaging for evaluating N status of winter wheat in the North China Plain. High-resolution images from a QuickBird satellite were taken on April 1, 2002 at booting stage of wheat with multi-spectral wavelengths (blue, green, red, and near-infrared). Correlation analyses indicated that all the broadband indices derived from the satellite images correlated well with sap nitrate concentration, SPAD readings, total N concentration, and aboveground biomass. The individual band reflectance values R, G, B correlated well with sap nitrate concentration, SPAD readings, total N concentration, and aboveground biomass. These results demonstrated the potential of using new generation high-resolution satellite imaging for large area wheat N status diagnosis.

Keywords:

• satellite image
• nitrogen
• growth status
• winter wheat

Acknowledgments

This research was financially supported by the Natural Science Foundation of China (Project number: 30571080, 30390084). We thank for Prof. Dr. Hailin Zhang in Oklahoma State University for his critical reading and correction of this manuscript.

Notes

∗Without straw recycling and optimized irrigation

^a The soil Nmin 0–30 cm for optimum N fertilization treatment (Treatment 2) before the 2001/2002 wheat sowing was higher than the 30 kg N ha^{− 1} so that no additional N fertilizer was applied before sowing.

^b The Nmin target from regreening to booting was 90 kg ha^{− 1}. Because at the regreening stage most roots grew in the 0–60 cm soil layer, the Nmin_{0 − 60} was used as the criterion for N application.

^c The Nmin target from booting to harvest was 110 kg ha^{− 1}. Because at the booting stage most roots grew in the 0–90 cm soil layer, the Nmin_{0 − 90} was used as the criterion for N application.

^a Means in a row with a different letter are significantly different using an LSD_0.05.

^b Dry matter.

^c NUE (N fertilizer use efficiency) % = [(Total N Uptake – Total N uptake of control plots with no N application for the current season)] ÷ Total N supply] × 100.