The research concerns the changes of spectral characteristics of reflected radiation (360 to 1 000 nm) of spring wheat leaves under nitrogen deficiency and moderate soil drought. The efficiency of factorial influence (η2) on chlorophyll index was equal to 20% and 4% under nitrogen and water deficiency, respectively. Most significantly soil drought influenced the water index WRI (η2=55%) and the light diffusion index R800 (η2=28%), which was caused by changes in leaf structure. At low levels of nitrogen supply, these parameters did not change or changed only slightly (η2=2%). It may be deduced that the data base for crop monitoring in precision farming systems must contain a series of optical criteria for assessing specific and non-specific changes in optical characteristics of a crop canopy under the impact of various stress factors.
