Chlorophyll meter predicts nitrogen status of tall fescue
1996
Kantety, R.V. | Van Santen, E. | Woods, F.M. | Wood, C.W.
The nitrogen (N) status of a crop can be used to predict yield and supplemental N fertilizer requirements, and rapid techniques for evaluating the N status of crops are needed. A study was conducted to determine the feasibility of using a hand held chlorophyll meter (SPAD 502, Minolta Co. Ltd., Japan) to monitor N status of tall fescue (Festuca arundinacea Schreb.). Four diverse tall fescue genotypes were grown at three locations in Alabama and fertilized at four N-rates from 0 to 336 kg ha-1. A similar experiment was conducted in the greenhouse using soil from the same field sites. Chlorophyll meter readings (SPAD) were taken, and extractable chlorophyll content, tissue N concentration and dry matter yield were determined at harvest. SPAD, extractable chlorophyll content, tissue N concentration, and dry matter yield increased quadratically (0.67 <R2 < 0.99) with increasing N fertilization in both experiments. All genotypes responded similarly to applied N, with some differences in magnitude. Relationships between SPAD meter readings and extractable chlorophyll and tissue N concentrations were linear with r2> 0.95. An additional independent variable, the square root of the inverse of SPAD, lowered the residual mean square by 11 and 16%, respectively, for tissue-N and chlorophyll concentrations, but did not increase the R2. This would be preferred for predictive purposes. Tissue N concentrations at higher N-rates were sufficient for maximum yield which occurred at 290 and 248 kg N ha-1 for greenhouse and field, respectively, but were lower than previously reported sufficiency values. The chlorophyll meter is an easy and efficient method of detecting tall fescue N status.
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