PSI PlantPen/N-Pen N 110, Инструкция по эксплуатации

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where R565 and R760 are reflectance values at indicated wavelengths. Based on a close relationship between NDGI and N-content in
barley leaves at mid-tillering stage (Fig. 3B), the NDGI index was proposed to be a convenient tool for determination of N-content and N-
nutrition state in barley (Klem, 2008).
Determination of NDGI index is strongly dependent on plant and leaf developmental stage as well as on environmental variability of field
cultivation. Especially the first rapidly expanding leaf and the older leaves at the onset of senescence exhibit high variability of NDGI
results. The most evident relationship between NDGI and N-content was reported in the second and the third youngest leaf (Klem 2008).
Fig. 3 Correlation between N content in barley dry matter and reflectance at particular wavelengths indicated as Pearsons correlation coefficient along
the reflectance spectrum (A). Relationship between NDGI index and N content in barley dry matter (B) can be interpreted as a sigmoid curve. Vertical
bars represent 95 % confidence intervals.
4.2 N-P
EN CONFIGURATION
The N-pen N 110 is configured to quantify reflectance of the leaf illuminated with two LED light sources (565 nm or 760 nm, Fig. 4),
calculate the NDGI index from average reflectance values and to predict the relative N-content in dry matter of plants or the postharvest
grain N- content. Due to differences in leaf structure of various crops, formulas for calculation of N content were developed specifically
for wheat, barley and corn. Each crop was tested on several varieties with similar results.
The N-Pen is pre-set by the manufacturer for a series of 10 measurements. After completing the series, the instrument calculates average
NDGI value and the corresponding nitrogen content in plant dry matter (%). The average value is then calculated as follows: the maximum
and minimum values are extracted and the average is calculated of the remaining eight values. If one (or more) of the 8 values significantly
differ from the rest (outliers), the device does not accept it (them) and asks you to repeat one or more measurements.
The outliers typically arise with high variability of measured values, eventual leaf damage, disease infection or inproper fixing of leaf to
measuring chamber. To exclude the outliers from the measurement the instrument uses Grubbs's test for outliers, where a t value is
calculated as the largest absolute deviation from the sample mean. The t value is then compared with critical values stated in the table
of Grubbs' critical values. If the calculated t value were higher than the critical value, the value is excluded due to high probability that
the value is an outlier.