Abstract
For profits in crop production, it is important to ensure that plants are not subjected to nitrogen stress (NS). Methods to detect NS in plants are either time-consuming (e.g., laboratory analysis) or require expensive equipment (e.g., a chlorophyll meter). In this study, a smartphone-based index was developed for detecting NS in plants. The index can be measured in real time by capturing images and processing them on a smartphone with network connectivity. The index is calculated as the ratio of blue reflectance to the combined reflectance of blue, green, and red wavelengths. Our results indicated that the index was specific to NS and decreased with increasing stress exposure in plants. Further, the index was related to photosynthesis based on the path analysis of several physiological traits. Our results further indicate that index decreased in the NS treatment due to increase in reflectance of red and green (or yellow) wavelengths, thus it is likely related to loss of chlorophyll in plants. The index response was further validated in strawberry and hydrangea plants, with contrasting plant architecture and N requirement than petunia.
Highlights
Nitrogen (N) is one of the major elements essential for plant growth, development, and quality.Maintaining optimal N concentration in the plant tissue is essential for increasing productivity and profitability in controlled environment agriculture (CEA)
Statistical analyses indicated that the environmental conditions were significantly different in the nitrogen stress (NS) and drought stress (DS) compared to C treatment (Table 1)
0.15 m3 ·m−3 was maintained in the DS treatment based on a previous work [30] that showed a decline in the growth of bedding plants including petunia at this level
Summary
Nitrogen (N) is one of the major elements essential for plant growth, development, and quality. Maintaining optimal N concentration in the plant tissue is essential for increasing productivity and profitability in controlled environment agriculture (CEA). In spite of supplying plants with optimal fertilizer solution concentration, plant N uptake can vary from pot to pot due to differences in substrate pH, leaching, water content, and crop growth. Monitoring N concentration of the plant tissue is more useful than measuring N concentration supplied to plants or present in the substrate, to ensure that plants are not exposed to N stress in CEA. Nitrogen concentration in the tissue can be measured in a laboratory. Plant sample analysis in a laboratory can be both expensive and time-consuming. Sensors recommended for indirect measurement of plant N status in CEA systems are expensive
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