Crop sensor readings in winter wheat as affected by nitrogen and water supply

Readings of optical crop sensors used for site-specific nitrogen management can be affected by both nitrogen and water supply of the crop. This may lead to wrong decisions in the on-line application of nitrogen. A winter wheat experiment was designed including nitrogen fertilization and irrigation as two factors. Results confirmed the influence of soil water availability on common vegetation indices and crop height, even though the dominating effect was nitrogen supply. To better discriminate these influences, images were taken by a conventional camera. Features derived by image analysis proved to be useful in addressing nitrogen and water supply.