| Nitrogen is one of the most important nutrients. It is the necessary matter for composing amino acid, protein, nuclear acid, chlorophyll and enzyme. Different nitrogen levels can induce the change of rice physiology. If rice lack nitrogen nutrition, it can not grow adequately, otherwise fertilizer will be wasted and environment will be polluted. So it is very important to manage nitrogen fertilizer effectively. Nitrogen management depends on evaluating nitrogen status of soil and crop accurately. All available nitrogen resource can be showed by crop growth status. So the nitrogen status of a crop is the best indicator for diagnosis nitrogen nutrition.The mostly traditional methods for diagnosis nitrogen nutrition of rice is chemical analysis based on vegetation tissue. Those methods have many disadvantages, for example, sampling, drying, weighting, wasting time and resource, harmful chemical, and so on. In order to research harmless and convenient methods for diagnosis nitrogen nutrition of rice, some methods outdoor were found. Up to now, two harmless and convenient methods were used widely, fertilizer windows methods and foliage color methods. Though they were harmless and convenient, the first one could not estimate how much fertilizer needed quantitatively, and the second one could not tell the true reason of yellowish.Remote sensing has been used in predicting chemical components of vegetation. Especially the higher resolution and magnitude information of hyperspectral data make it possible to identification and classification of vegetation, monitor crop growth status and fertility of cropland. Study on some characters of biophysics and biochemistry for vegetation has become one of the most important tasks of hyperspectral remote sensing. Spectral determination has proved an automatic, quick and nondestructive method for assessment ofnutrition, and the spectral discriminability of the treatments demonstrated the feasibility to evaluate rice N status in field by canopy spectral determination and the potential for detecting rice N status in a wide area by using multispectral remote sensing.In this study, in order to research the mechanism of estimate rice N status, we studied the relationship between hyperspectral data and rice nitrogen concentration. The significant differences for rice nitrogen concentration , hyperspectral reflectance, and multispectral data were studied as well. Results showed that there was instability relationship between hyperspectral data and nitrogen concentration for different varieties, growth stage and environment. So new ideal but not hyperspectral data itself was used to find available methods evaluating rice N status as follows: There are two character parameters for the first derivative of red edge spectral reflectance, red edge slope, and red edge position. The relationship between red edge slope and chlorophyll concentration has been proved by many researchers. And relationship between chlorophyll concentration and nitrogen concentration has been proved too. Relationship has been found between red edge position and leaf area indices, and red edge position was related to nitrogen concentration indirectly. However, those relationships were changing with different varieties, growth stage and environment. It is necessary to find new methods to estimate rice N status using red edge slope and red edge position of the most upper fully expended leaf and the third one. Results indicted a new vegetation index which calculated from red edge slope and red edge position of the first and the third fully expended leaves. And ideal results were drawn using the new vegetation index evaluating rice N status at different varieties, growth phases, and environment. Many factors affect leaf spectral reflectance including foliage chemistry composing, cell structure, water content, and so on. The theory of continuum- removed, which has been used in mineral spectral reflectance, was introduced. And some studies on continuum- removed method s...
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