Relationship Between the Normalized SPAD Index and the Nitrogen Nutrition Index: Application to Durum Wheat |
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Authors: | P Debaeke P Rouet E Justes |
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Institution: | UMR 1248 Institut National de la Recherche Agronomique (INRA), Ecole Naitionale Supéríeure d'Agronomie de Toulose (ENSAT) , Castanet-Tolosan Cedex, France |
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Abstract: | In a three-year field experiment in Toulouse (in Southwest France), two indicators of plant nitrogen (N) status were compared on five durum wheat cultivars: the normalized SPAD index and the nitrogen nutrition index (NNI). SPAD value is a non-destructive measurement of chlorophyll content from the last expanded leaf. The normalized SPAD index is expressed relative to SPAD reading on a fully fertilized crop. The NNI is calculated from the crop biomass and total plant N content using a universal N-dilution curve for wheat. The normalized SPAD index and NNI were closely related irrespective of year, cultivar, and growth stage. When N was a limiting factor, the SPAD index measured at anthesis predicted grain yield and protein content accurately. Unlike NNI, SPAD index cannot be used to predict these variables when wheat is over-fertilized. |
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Keywords: | SPAD nitrogen nutrition index durum wheat plant N status grain protein content chlorophyll meter |
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