Abstract:

Greenness of leaves can reflect nitrogen level of crops due to the close relationship between leaf color and nitrogen (N) content. The objective of this study was to quantify rice leaf greenness and reveal its relationship with N status through digital camera and image processing technology. We utilized a digital camera to take rice leaf photos of different varieties and N rates, and then compared the image feature parameters like hue (H), value (V) and dark green color index (DGCI) with SPAD readings and leaf N content. Results showed good linear correlation between the H, V, and DGCI parameters and SPAD readings. The r2 between DGCI and SPAD readings was 0.62** and 0.60** at shooting and booting stage, respectively. The image feature parameters were also linearly correlated with leaf N content. The r2 between leaf N content and H, V, DGCI were 0.53**, 0.63**, 0.59** at booting stage, respectively. Booting stage was more proper than shooting stage while assessing the rice N status, and V was most stable among the three parameters, thus was optimal indicator.