Adjustment for Specific Leaf Weight Improves Chlorophyll Meter's Estimate of Rice Leaf Nitrogen Concentration

The chlorophyll meter provides a simple, quick, and nondestructive method to estimate leaf N status of rice (Oryza sativa L.), but the linear relationship between leaf N concentration on a dry-weight basis (N dw ) and the meter reading differs depending on developmental stage and genotype. The objective was to determine whether prediction of N dw with the chlorophyll meter can be improved by a simple correction for specific leaf weight (SLW). Leaf N status was estimated by a chlorophyll meter (SPAD-502) and measured directly by micro-Kjeldahl procedure. Specific leaf weight was calculated as the ratio of dry weight to leaf area. In one field study with 'IR72', measurements were taken at midtillering, panicle initiation, and flowering stages on the uppermost fully expanded leaves of both N-deficient and N-sufficient plants [...]