Sunscan Canopy Analysis System by Delta-T Devices is developed primarily for regular and short canopies such as rice, wheat crops, grasslands. It calculates LAI based on light (photosynthetically active radiation – PAR) measurements above and below canopy.
The instrument has two sensors : 1. Beam fraction sensor (BSF) that measures direct and diffuse incident radiation above the canopy; 2. Linear probe that has 64 to 80 equidistant calibrated photodiodes measuring PAR flux below the canopy. Having two sensors to measure above and below canopy radiation measurements simultaneously enables users to take measurements even under partially overcast skies. LAI is calculated by inverting Beer’s law equation. This requires calculation of extinction coefficient which is in turn calculated as a function of leaf angle distribution. Leaf angle distribution parameter can be chosen based on type of the canopy.
The instrument has been proven to measure LAI with good accuracy in crops such as maize and rice, also in Poplar plantations. However, its application is limited especially in forested areas where woody branches and stems would lead to overestimated LAI. Furthermore, it is also inconvenient assembly for measurements (BFS needs to be in open patch) that restricts its application in forests.
Oguntunde, P. G., Olukunle, O. J., Fasinmirin, J. T. & Abiolu, O. A. Performance of the SunScan canopy analysis system in estimating leaf area index of maize. Agric. Eng. Int. CIGR E-J. 14, 8 (2012).
Sone, C., Saito, K. & Futakuchi, K. Comparison of Three Methods for Estimating Leaf Area Index of Upland Rice Cultivars. Crop Sci. 49, 1438 (2009).
Tripathi, A. M. et al. Evaluation of Indirect Measurement Method of Seasonal Patterns of Leaf Area Index in a High-Density Short Rotation Coppice Culture of Poplar. Acta Univ. Agric. Silvic. Mendel. Brun. 64, 549–556 (2016).