Optical leaf area index measurement as a tool for characterizing crop growth at the field scale.
1994
Pampolino M.F. | Dobermann A.
Indirect methods for determination of crop growth indices may be used as alternatives for measuring growth curves and/or growth variability of field crops. In this study, an optical sensor (LAI-2000) was tested for rapid measurement of leaf area index (LAI) of transplanted rice (Oryza sativa L.) under field conditions and compared with destructive crop sampling methods. Before panicle initiation, errors in LAI measurement tended to be relatively large, but significantly decreased with closing canopies. Measured LAI was highly correlated to dry matter and grain yield (r=0.81-0.96) at different growth stages and seems to be a suitable method for quick yield estimation in farmers fields. Direct and indirect measurements of LAI were significantly correlated (r=0736). Grain yield (GRY) ranges of 2.4-5.9 t/ha and 4.5-8.8 t/ha were measured within an unfertilized and fertilized field, respectively. CV's of several crop variables ranged from 13-21 percent. Most of the variation in dry matter yield (DMY) and GRY occurred over short distances (<2.5-3 m) and procedural errors associated with destructive sampling and determination methods significantly increased the prediction error of interpolated yield maps. Indirect LAI measurement was a better choice for characterizing and mapping crop growth variation than using destructive sampling.
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