Optical characteristics of the spring wheat leaves under the nitrogen and water deficiency conditions
Keywords:
wheat, reflection indexes, nitrogen and water deficiency, stressAbstract
Incomplete use of remote-sensing instruments essentially limits possibilities of precision agriculture technologies. The water deficit and its uneven distribution across the field can distort results of a remote sensing estimation of plant fertilizer requirements. The objective of this study was to estimate specific and nonspecific changes of optical characteristics of plants at nitrogen and water deficit. To eliminate possible impact of various adverse environmental factors on plants experiments were conducted under controlled conditions. Winter wheat (Triticum aestivum L., cultivar Krasnoufimskaya 100) was grown in the 5L containers filled with a sod-podzol soil. Fertilizer was applied before sowing to create optimum and deficiency level of a nitrogen supply. Soil water content was equal to 80% of total field capacity (control). In the period from the completion of booting to the earing stage soil moisture content was maintained 30 % and 50 % of total field capacity. Spectral characteristics of radiation reflected from leave were registered by a spectrometer HR2000 (Ocean Optics, USA). 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 (?2) on chlorophyll index was equal to 20% and 4% under nitrogen and water deficiency, respectively. Most significantly, soil drought influenced the water index (?2=55 %) and the light diffusion index (?2=28 %), which was caused by changes in leaf structure. At low levels of nitrogen supply, these parameters did not change or changed only slightly (?2=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.
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