Application of Computer-Aided Cotton Leaf-Color Analysis in Nitrogen Status Diagnosis in Cotton Plants

Different N nutrition cotton canopy is deduced by different N fertilizer application, and cotton canopy images were captured by using a digital camera.Cotton canopy spectrum character is computer-aided measured and the relationship between cotton N application and its canopy spectrum is studied as well.Results indicated that with the increasing of N application, red spectrum flux of cotton canopy is decreased but blue, green flux is increased. An integrated index, viz., B/(G+R), could sensitively reflect cotton N application variation, hence it is a good index of cotton N diagnosis in computer-aided cotton leaf color analysis. Results also indicated that some background noises, such as light intensity, soil background have small effect on correlations between B/(G+R) and cotton N application, but angle of image-taking have significance effect on the correlation between B/(G+R) and cotton N application. In order to take precise diagnosis results, the angle of image-taking should be fixed by 30°. The study also indicated that both full budding and full flowering period are feasible to practice computer-aided leaf-color analysis and diagnose cotton N status.