4Evans J R. Nitrogen and photosynthesis in the flag leaf of wheat.Plant Physiology, 1983, 72: 297-302.
5Blachmer T M, Schepers J S. Techniques for monitoring crop nitrogen status in corn. Communications in Soil Science and Plant Analysis, 1994, 25:1 791-1 800.
6Daughtry C S T, Walthall C L, Kim M S, de Colstoun E B,McMurtrey J E. Estimationg corn leaf chlorophyll concentration from leaf and canopy reflectance. Remote Sensing of Environment,2000, 74: 229-239.
7Walburg G, Bauer M E, Daughtry C S T, Housley T L. Effects of nitrogen on the growth, yield, and reflectance characteristics of corn.Agronomy Journal, 1982, 74: 677-683.
8Ma B L, Morrison M J, Dwyer L M. Canopy light reflectance and field greenness to assess nitrogen fertilization and yield of maize.Agronomy Journal, 1996, 88: 915-920.
9Osborne S L, Schepers J S, Francis D D, Schlemmer M R. Detection of phosphorus and nitrogen deficiencies in corn using spectral radiance measurements. Agronomy Journal, 2002, 94:1 215-1 221.
10Knipling E B. Physical and physiological basis for the reflectance of visible and near-infrared radiation from vegetation. Remote Sensing of Environment, 1970, 1: 155-159.