Analysis of hyperspectral on super high-yielding maize under different nitrogen levels

Agricultural hyperspectral remote-sesing approaches have been proposed for the study of crop growth and development. The objective of this study was to clarify the hyperspectral on super high-yielding summer maize and give support to the study on super high-yielding maize growth. The experiment was conducted in the growing season of summer maize in 2009 at the Corn Research Centre of Huanghuaihai,Shandong Agricultural University. The experiment included two cultivars ( DH661 and ZD958) and four levels of nitrogen ( N) application( 0,150,300 and 450 kg/hm2 respectively) . The differences of hyperspectral canopy reflectance between super high-yielding maize and general maize,the relativity between hyperspectral canopy reflectance and dry matter accumulation,chlorophyll content were analyzed. The results showed that the reflectance at near-infrared wavebands of super high-yielding summer maize was higher than that of general maize and slower change in the later growth period. It was related to the higher dry matter accumulation and chlorophyll content of high-yielding maize in the later growth period. Hyperspectral canopy reflectance of super high-yielding maize showed an increasing trend with the increases of nitrogen fertilizer. The difference under different level was not significant due to the higher fertilizer-bearing and less sensitivity of chlorophyll content to nitrogen fertilizer. The double-peak phenomena for red edge parameters of super high-yielding was similar to that of general maize and showed a decreasing trend with the change of development period. There was a red edge platform' phenomenon for the position of red edge between flowering period and filling period. It showed that super high-yielding maize had a longer growth vigorous period than that of general maize. The blue shift of position of red edge was similar to that of general maize,but its change was less than that of general maize. Meanwhile,red edge slope ( Dred) and red edge area ( Sred) were higher than that of general maize under different nitrogen levels. Some hyperspectral wavebands were chose to calculate RVI ( Ratio Vegetation Index) ,DVI ( Difference Vegetation Index) and NDVI ( Normalised Difference Vegetation Index) ,the correlation between the vegetation index and dry matter accumulation above ground and chlorophyll content was analyzed. The results indicated that the correlation between many vegetation index and dry matter accumulation above ground were significant ( r( 0. 01,30) = 0. 513) . Among these vegetation indices,the NDVI with four bands ( 760nm,810nm,870nm,and 950nm respectively) was the best to predict the dry matter accumulation of super high-yielding maize. The correlation between vegetation index with visible wavebands ( 510nm,560nm,and 710nm) ,near-infrared bands( 810nm,870nm,950nm) ,and chlorophyll content was significant. Meanwhile,the significant correlation between position of red edge and chlorophyll content, chlorophyll a content,chlorophyll b content,carotenoid content was showed. The correlation between red edge slop,red edge area,and dry matter accumulation of super high-yielding was significant. The results also showed that red edge slop and red edge area could be used to predict chlorophyll content and chlorophyll a content of super high-yielding maize. Overall,the hyperspectral canopy reflectance had a large difference between super high-yielding maize and general maize. The hyperspectral canopy reflectance and position of red edge of super high-yielding maize were not sensitive with the increases of nitrogen fertilizer. The results could give support to the study of physiological property of super high-yielding maize.