Effect of leaf phosphorus and potassium concentration on chlorophyll meter
1997
Sanico, A.L. | Shaobing Peng | Garcia, F.V. | Descalsota, J.P. | Cassman, K.G. (International Rice Research Inst., Los Banos, Laguna (Philippines). Agronomy, Plant Physiology and Agroecology Div.)
The chlorophyll meter (SPAD 502) is a convenient tool to estimate the leaf chlorophyll and nitrogen (N) content of a crop. Previous studies indicated that leaf thickness affects SPAD reading. This study aimed to determine the effect of leaf phosphorus (P) and potassium (K) concentrations on SPAD reading. In the 1996 dry season, IR72 was grown at IRRI and PhilRice under various fertilizer levels in randomized complete block design. At IRRI, the following fertilizer rates (NPK kg/ha) were used: 0-0-0, 0-25-0, 0-0-40, 210-0-0, 210-25-0, 210-0-40, and 210-25-40. At PhilRice, NPK rates (kg/ha) were 0-0-0, 0-30-50, 210-0-0, 210-30-0, 210-0-50, and 210-30-100. Nitrogen fertilizer was applied in four splits: before transplanting, midtillering, panicle initiation and flowering. Phosphorus and K fertilizers were applied as basal. SPAD measurements were made on the topmost fully expanded leaves at midtillering and panicle initiation. The leaves were then detached, dried and analyzed for N, P, and K. Significant responses to fertilizer N and P were observed at IRRI and PhilRice. Plants responded to fertilizer K at PhilRice but not at IRRI. The SPAD value was highly correlated with leaf N concentration (r square = 0.87-0.90) at midtillering and panicle initiation. Severe P deficiency reduced leaf N concentration more than SPAD value at mid-tillering. At panicle initiation, the direct effect of P on SPAD reading was negligible
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