Leaf and canopy optical characteristics as crop‐N‐status indicators for field nitrogen management in corn |
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Authors: | Lisandro Rambo Bao‐Luo Ma Youcai Xiong Paulo Regis Ferreira da Silvia |
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Affiliation: | 1. Eastern Cereal and Oilseed Research Centre (ECORC), Central Experimental Farm, Agriculture and Agri‐Food Canada, Research Branch, 960 Carling Avenue, Ottawa, Ontario, Canada K1A 0C6;2. Federal University of Rio Grande do Sul (UFRGS), Agronomy, Crop Science Department, 3. Mail Box 4. 15.100, Zip Code 90970‐000, Porto Alegre, RS, Brazil;5. Syngenta Seeds Ltda, Uberlandia, MG, Brazil;6. MOE Key Laboratory of Arid and Grassland Ecology, Lanzhou University, Lanzhou 730000, China |
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Abstract: | The primary constraint of predicting the economic optimum nitrogen rate (EONR) for corn (Zea mays L.) is the high variability of soil nitrogen (N) supply due to environments, soil types, manure, and cropping histories. Portable instruments have been developed to measure leaf and canopy optical characteristics for determining plant N status. The objectives of this field study were to: (1) evaluate leaf and canopy optical properties including transmittance, reflectance, and fluorescence as indicators of corn N status with soil types, developmental stages, and N‐application rates, (2) compare the efficiency of two commercial radiometers that are designed to measure canopy reflectance, and (3) assess the constraints of these crop‐based indicators as a possible guide for real‐time N sidedressing in corn. Field experiments with different levels of N, soil types, and corn hybrids were conducted at three sites in Ottawa, ON, Canada, in 2004 and 2005. Leaf chlorophyll concentrations (SPAD chlorophyll meter), chlorophyll fluorescence (OS‐30), leaf area, and canopy reflectance (NDVI measured by CropScan and GreenSeeker radiometers) were simultaneously measured at several growth stages, while grain yield was determined at harvest. Our results show that canopy reflectance (NDVI) displayed similar efficiency as an indicator of N status on both soil types and corn hybrids in the two consecutive years. The chlorophyll readings often differentiated N‐deficient from N‐sufficient plots and therefore were a promising indicator for predicting corn N requirements. The fluorometer device evaluated in this study was unable to characterize corn N status. |
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Keywords: | canopy reflectance chlorophyll fluorescence nitrogen nutrition grain yield Zea mays |
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