Non-destructive Estimation of Rape Nitrogen Status Using SPAD Chlorophyll Meter

Chlorophyll meter, soil plant analysis development (SPAD) is a simple, portable diagnostic tool that measures the greenness or relative content of leaves. The objective of this study was to analyze the SPAD change rule with the different growth stage and different fertilizers to the rape. The SPAD distribution map in a representative rape was tracked and analyzed, and the spatial SPAD distribution map in a given leaves was obtained by using the interpolate grid functions of geographic information system (GIS) software. The experiment was conducted in the farm of Zhejiang University. Three nitrogen fertilizers and two repeated experiments were carried on in this research. Tracking experiment was started from 21st March 2005 to 28 April 2005. In order to delay tracking time, the expanded leaves in the third branches from the top was chosen and tracked. The result shows that different growth stages and different fertilizers have different SPAD values, but the change rule is regular, which will be beneficial for the further nitrogen management. Spatial SPAD distribution maps of the leaves will be useful for the development of digital farming and further analyzing the internal SPAD distribution