title: [Study on the correlation of spectral characteristic and nitrogen content of the soil in citrus orchard of three Gorges Reservoir Area].
abstract: The relationship between the spectrum characteristics and nitrogen content of soils in citrus orchard of the Three Gorges Reservoir Area was studied by analyzing the visible-near infrared spectrum. The results showed that the soil reflectivity in creased lineally as the wavelength increases across the visible spectrum and reached a stable plateau in the short wavelength near-infrared region (780-1750 nm)without much fluctuation. In the long wavelength near-infrared region (1750-2400 nm) the reflec tivity of the soils was higher with higher fluctuation. There were three strong absorbance peaks around 1416, 1913 and 2209 nm, respectively, in the long wavelength infrared region. Soil available nitrogen content and total nitrogen content were positively correlated with soil light reflectivity but negatively correlated with catoptric-spectrum values reciprocal logarithm. At 541 nn of visible light region, a high positive correlation was found between the available nitrogen content and the first derivative of the soil reflective spectrum with a correlation coefficient of + 0.605** and the best fitting equation was y = 2E + 09x(2) - 3E + 06x + 890.49, where R2 = 0.5, and x is the first derivative of the soil reflective spectrum. At 1909 nm of the near-infrared long wavelength region, the correlation between the total nitrogen content and the reciprocal-log values of the reflective spectrum of the soils was the best with a correlation coefficient of -0.612**, and the best fitting equation was y = 1.3721x(2) - 2.1075x + 0.8592, where R2 = 0.4, and x is the reciprocal values of the log reflective spectrum of the soils.
authors: Citrus Research Institute, Southwest University, Chongqing 400712, China. yishilai@126.com
authors: Shi-lai
authors: SL
authors: Yi
authors: Lie
authors: L
authors: Deng
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authors: SL
authors: He
authors: Yong-qiang
authors: YQ
authors: Zheng
authors: Rang-jin
authors: RJ
authors: Xie
authors: Xuan
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authors: Zhang