Nondestructive Measurement Method of Leaf Area Index Using Near-infrared Radiation and Photosynthetically Active Radiation Transmitted through a Leafy Vegetable Canopy

Because the leaf area index (LAI) is an essential parameter for understanding structure and growth status of plant canopies, nondestructive continuous estimation methods have been required. Recently, LAI method using ratio near-infrared radiation (NIR; 700–1000 nm) to photosynthetically active (PAR; 400–700 (NIR in /PAR ) transmitted through a canopy has proposed. However, because previous studies on this NIR -based are limited tall plants (e.g., forest rice canopies), study, we applied short (i.e., spinach) investigated its validity. three other traditional indices indirect estimation—relative PPF density (rPPFD), normalized difference vegetation (NDVI), simple (SR)—were measured 25 canopies with different LAI. showed better sensitivity ( R 2 = 0.88) observed than indices, particularly when was greater 3 m ·m −2 . In addition, estimated from at 10-min intervals entire period could capture increasing trend throughout stage (mean absolute error 0.87 ). Errors long-term estimations may be caused by sensor location insufficient data due unsuitable weather conditions measuring The current study demonstrates merits limitations low height thereby contributing practical use horticultural crops.