Nitrogen determination in pepper (Capsicum frutescens L.) plants by color image analysis (RGB)

In order to investigate the suitable index of the diagnosis of pepper plants nitrogen status by color image analysis, a field experiment was conducted. In this study, six levels of nitrogen fertilization were established so as to induce nitrogen status in pepper plants. At the flowering and fruiting stages, total nitrogen was evaluated by laboratory analysis. The chlorophyll index was determined using a soil plant analysis development (SPAD)-502 chlorophyll meter. Also, color images were taken with a digital camera; the color images were processed in order to determine the averages of the red (R), green (G) and blue (B) colors. The result show that there were significant negative relations between G/(R+G+B) ratio of coverage image and the indexes of pepper nitrogen status, for example inorganic nitrogen in soil, total nitrogen of plant, nitrate concentration of leafstalk and SPAD readings at flowering and fruiting stages. Color image analysis provides an accurate and quick way for nitrogen estimation in pepper plants. Key words: Pepper, color image analysis (RGB), nitrogen status.