Image analysis estimation of leaf area index and plant size of young hazelnut plants

A nondestructive method of leaf area estimation was evaluated on two year old hazelnut plants cv. Tonda Gentile Romana grown in the field. Black and white photographs of 22 plants were taken from two directions at 90 degrees and processed by means of a Vidas image analyzer (Kontron Elektronic) to obtain an estimation of leaf area. Plants were then defoliated and actual leaf area was measured by means of a Delta T Device area meter. A good linear relationship between measured leaf areas and canopy silhouette areas was obtained. Nevertheless, silhouette area measured through image analysis resulted consistently lower than actual leaf area, because of leaf angle distribution and the overlapping of the different leaf layers. Leaf area index (LAI(plant)) was reliably calculated as the ratio between total leaf area estimated by image analysis and the area of canopy projection on the ground. Plant size parameters (height, width, canopy cross-sectional area and volume) were correctly predicted by image processing. Once calibrated, the method is simple and rapid and seems to be an effective tool for measurements of within-crown leaf area index and plant growth repeated in time and space.