Development of LAI and fruit load estimation method using a three-dimensional shape measurement sensor

The productivities of tomato (Solanum lycopersicum L.) and sweet pepper (Capsicum annuum L.) are greatly influenced by the amount of light received, which is the basis of photosynthesis, and by cultivation management based on the determination of the plant's fruit load. Producers estimate the two factors based in visual cues and growth measurements conducted weekly. However, if such factors could be assessed using equipment, cultivation management could be optimized, which would further increase yield. In the present study, we assessed leaf area index (LAI) trends in a tomato crop in a horticultural facility using a Kinect camera for Windows, and estimated the amount of light received by the crop. In addition, we investigated leaf area trends based on layers in sweet pepper and examined to the potential for fruit load assessment. It was shown that if the LAI is ≤3 in tomato, the actual LAI can be estimated from the proportion of projected area measured using Kinect per unit area. The LAI of tomato was controlled and shifted from 2 to 3 in the greenhouse of the producer, and we were able to measure LAI during the cultivation period by Kinect and calculate the amount of light received. To evaluate the fruit load of sweet pepper, we investigated the percentage abortion of flower and fruit, weekly plant height extension, and projected leaf area for each layer during the cultivation period. Consequently, it was shown that the abortion of flower and fruit had a stronger correlation with the ratio of projected leaf area within 40 cm from the growing point relative to the total projected leaf area. It was suggested that Kinect is useful for predicting fruit load of sweet pepper.