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United States Department of Agriculture

Agricultural Research Service

Title: Changes in Spectral Reflectance of Wheat Leaves in Response to Specific Macronutrient Deficiency

Authors
item Ayala-Silva, Tomas
item Beyl, Caula - ALABAMA A&M UNIVERSITY

Submitted to: Advances in Space Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 17, 2004
Publication Date: December 16, 2004
Citation: Ayala Silva, T., Beyl, C.A. 2004. Changes in Spectral Reflectance of Wheat Leaves in Response to Specific Macronutrient Deficiency. Advances in Space Research.

Interpretive Summary: In wheat (Triticum aestivum L.) plants, deficiency of a vital element may drastically affect growth, appearance, and most importantly yield. This study, evaluated the growth of wheat in controlled environments. Information about nutrient deficiencies in crops grown in controlled environment is essential to optimize food productivity. The main purpose of this study was to determine whether deficiency of major macronutrients alters spectral reflectance properties of wheat leaves. Plants were grown in the greenhouse and growth chamber, in a modified Hoagland's nutrient solution. Spectral reflectance of fully expanded wheat leaves from 280 nm to 1100 nm, nutrient concentrations (N, P, K, and Ca) and chlorophyll (Chl) were determined when deficiency symptoms were first evident (* 6-7 weeks). Chlorophyll content and fresh and dry weight, were used to assess the severity of the nutrient stress. All nutrient deficiencies affected chlorophyll content and generally increased reflectance in the visible (VIS) 400-700 nm and infrared (IR) 700 nm to 1100 nm ranges. Magnesium and nitrogen deficiencies had the most pronounced effect on chlorophyll concentration height, and reflectance. Major nutrient deficiencies tested reduced chlorophyll concentration, increase reflectance in the visible range and caused a shift in the position of the red edge (the point of maximum slope on the reflectance spectrum of vegetation between red and near-infrared wavelengths) toward shorter or longer wavelengths depending upon the element. In the greenhouse, N and Mg induced the larger increase in reflectance of 33% and 25% in the VI range and 86% and 53% in the IR range, respectively. However, in the growth chamber, an increase of 97% and 25% occurred in the VI range, and 20% and 33% in the IR range, respectively. In the IR range in the growth chamber, P, K, and Ca deficiency showed a reduction in reflectance (412 to 770 nm). This research indicates that mineral deficiencies and reflectance may not specific to one environment and could have consequential implications for the design of CELSS in space, and perhaps the future of land base agriculture.

Technical Abstract: In wheat (Triticum aestivum L.) plants, deficiency of an essential element may drastically affect growth, appearance, and most importantly yield. Wheat, the focus of this study, is one of the crops studied in the CELSS program. Information about nutrient deficiencies in crops grown in controlled environment is essential to optimize food productivity. The main objective of this study was to determine whether deficiency of Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca) and Magnesium (M) alters spectral reflectance properties of wheat leaves. Plants were grown in the greenhouse and growth chamber, in a modified Hoagland's nutrient solution. Spectral reflectance of fully expanded wheat leaves from 280 nm to 1100 nm, nutrient concentrations (N, P, K, and Ca) and chlorophyll (Chl) were determined when deficiency symptoms were first evident (* 6-7 weeks). Chlorophyll content and fresh and dry weight, were used to assess the severity of the nutrient stress. All nutrient deficiencies affected chlorophyll content and generally increased reflectance in the visible (VIS) 400-700 nm and infrared (IR) 700 nm to 1100 nm ranges. Magnesium and nitrogen deficiencies had the most pronounced effect on chlorophyll concentration height, and reflectance. All macronutrient deficiencies tested reduced chlorophyll concentration, increase reflectance in the visible range and caused a shift in the position of the red edge (the point of maximum slope on the reflectance spectrum of vegetation between red and near-infrared wavelengths) toward shorter or longer wavelengths depending upon the element. In the greenhouse, N and Mg induced the greatest increase in reflectance of 33% and 25% in the VI range and 86% and 53% in the IR range, respectively. However, in the growth chamber, an increase of 97% and 25% occurred in the VI range, and 20% and 33% in the IR range, respectively. In the IR range in the growth chamber, P, K, and Ca deficiency caused a reduction in reflectance (412 to 770 nm). This research indicates that mineral deficiencies and reflectance are not specific to one environment and could have important implications for the design of CELSS in space, and perhaps the future of terrestrial agriculture.

Last Modified: 7/25/2014
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