关键词: 紫花苜蓿, 氮肥, 冠层光谱反射率, 植被指数, 模型

Abstract: Spectral reflectance characteristics of alfalfa (Medicago sativa L.) canopy under different nitrogen levels were studied in this research. Relationships between the nitrogen contents of aboveground organs and the vegetation indices (RVI, DVI, NDVI and RDVI) of visible wavelengths (510 nm, 560 nm, 610 nm, 680 nm, 710 nm, and 760 nm), and near infrared wavelengths (810 nm, 870 nm, 950 nm) were analyzed. The spectral prediction model of nitrogen contents of alfalfa leaves, buds and plants were established respectively in budding period. Results showed that vegetation index established by 760 nm, 810 nm and 870 nm had better correlation with the nitrogen contents of aboveground organs. The optimal spectral prediction model was determined by comparison, which was vegetation index DVI(760, 810) prediction model, and adjusting R² was 0.919, average relative error was 9.1%. Therefore,spectral prediction models established for evaluating the nitrogen contents of alfalfa in this research might provide a basis of decision making for the nutritional diagnosis and fertilization of alfalfa in Xinjiang.

Key words: Alfalfa, Nitrogen, Canopy spectral reflectance, Vegetation index, Model