Improvement of nitrogen management in rice paddy fields using chlorophyll meter (SPAD) |
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Authors: | M. Esfahani H. R. Ali Abbasi B. Rabiei M. Kavousi |
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Affiliation: | (1) Department of Agronomy and Plant Breeding, Faculty of Agricultural Sciences, University of Guilan, P.O. Box 41635-1314, Rasht, Iran;(2) Rice Research Institute of Iran (RRII), P.O. Box 3657, Rasht, Iran |
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Abstract: | Optimum rate and timing application of nitrogen (N) fertilizer are most crucial in achieving high yield in irrigated lowland rice. In order to assess leaf N status, a semidwarf rice cultivar (Khazar) was grown with different N application treatments (0, 40, 80, and 120 kg N ha−1 splited at transplanting, midtillering, and panicle initiation stages) in a sandy soil in Guilan Province, Iran, in 2003. The chlorophyll meter (SPAD 502) readings were recorded and leaf N concentrations were measured on the uppermost fully expanded leaf in rice plants at 10-day internals from 19 days after transplanting to grain maturity. Regression analysis showed that the SPAD readings predicted only 23% of changes in the leaf N concentration based on pooled data of leaf dry weight (N dw) for all growth stages. However, adjusting the SPAD readings for specific leaf weight (SPAD/SLW) improved the estimation of N dw, up to 88%. Specific leaf weight (SLW), SPAD readings, leaf area and weight as independent variables in a multiple regression analysis predicted 96% of the N dw changes, while SPAD readings independently predicted about 80% of leaf N concentration changes on the basis of leaf area (N a). It seems that chlorophyll meter provides a simple, rapid, and nondestructive method to estimate the leaf N concentration based on leaf area, and could be reliably exploited to predict the exact N fertilizer topdressing in rice. |
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Keywords: | Chlorophyll meter (SPAD) N fertilizer topdressing Nitrogen management Rice |
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