Image Sensing, A Unique Tool for Early Detection of Nitrogen Deficiency of Tomato Grown in Hot and Humid Greenhouses

Abstract

Protected culture (PC) answers the major issues in conventional agriculture, and thus helps feed the rising world population. Meanwhile, soilless culture has become an integral part of the PC, for sake of catering to the plant nutrient requirements precisely. Therefore, innovative intellective diagnostic systems for diagnosing nutrient deficiency symptoms in protected culture is a timely need. Hence this experiment was conducted to test the effectiveness of “Image Sensing” as a diagnostic tool for nitrogen deficiency under semi-intensive greenhouse management in hot and humid weather. In this study N deficiency symptoms of tomato were detected by leaf color changes, identified through image sensing, and the deficiency was confirmed with respect to retardation of plant growth. Tomato plants were subjected to a series of N treatments by providing 200, 100, 50, 25, and 12.5 percent of the recommended N supply for soilless culture tomatoes. The results showed that morphology changes like stem thickness, leaf area, plant height, and leaf number were significantly reduced along with a reduction of N supply (p<0.05) beginning from 5th week after transplanting (WAT). Leaf images were processed in “ImageJ”, software” to determine the green color intensity of leaves. Image analysis showed that there was a significant difference among treatments since the 3rd WAT. The leaf color chart was less effective for distinguishing leaf color at the early stages of N deficiency. The results revealed that diagnosis of N deficiency in tomato leaves could be effectively done by image sensing much earlier than the use of plant growth parameters or morphological changes. Hence, image sensing can be used as a more effective diagnostic tool for early detection of N deficiency of tomato cultivations in hot and humid greenhouses, that can be used to improve crop management, especially in large large-scale commercial practices.