Food scarcity, population growth, and global climate change have propelled research to enhance crop yield growth. Field crop phenotyping provides important information to explain crop growth and its relationship with the environment.

However, the traditional vehicle-mounted platforms used for field experimental sampling and determination of crop character parameters are laborious, time-consuming, and limited in terms of space coverage. This limits the rapid development of crop science research.

Given its flexibility, low cost, and wide space coverage, the high-throughput, near-earth remote sensing phenotyping platform represented by Unmanned Aerial Vehicles (UAV) has become an effective way to obtain field phenotypic information.

Assessing the plant phenotypic characteristics with spectral data

Specim AFX10 hyperspectral imaging system was integrated into the Ecodrone® UAS-8 platform manufactured by Beijing EcoTech Ecological Technology Ltd. to evaluate the growth potential of winter wheat in North China.

The Specim AFX10 works in the wavelength range from 400 to 1000 nm and has a high spectral and spatial resolution, high sensitivity, and high signal-to-noise ratio. It is particularly suitable for performing a spectral analysis of wheat based on the light it reflects. The spectral data enables further analysis of the phenotypic characteristics of the wheat.

Normalized Difference Vegetation Index (NDVI)* and Plant Senescence Reflectance Index (PSRI)** of wheat in different periods were observed by collecting spectral data of wheat in different periods. In the later stage, the fertilizer application rate and harvest time can be determined by combining the relationship between the reflection index, nitrogen content, and grain maturity.

Hyperspectral imaging UAV remote sensing system has high value and broad application prospects in agricultural production to protect and predict crop growth. The high spectral resolution of the Specim AFX enables also the early detection of some pests and diseases and the monitoring of their evolution on the crops.

* Normalized Difference Vegetation Index
The Normalized Difference Vegetation Index (NDVI) parameter reflects crop growth and nutritional information. According to the NDVI parameter, we can tell what the crop’s nitrogen demand in different seasons is. This information can guide the rational application of nitrogen fertilizer. The NDVI was calculated as follows. R840 is the reflectance in the band of 840nm in the near-infrared (NIR) region. R668 is the reflectance in the band of 668nm in the red region.

NDVI = (R840 – R668) / (R840 + R668)

** Plant Senescence Reflectance Index
The Plant Senescence Reflectance Index (PSRI) can be used for vegetation health monitoring, plant physiological stress monitoring, crop production, and yield analysis. The PSRI was calculated as follows. R800 is the reflectance in the band of 800nm in the near-infrared (NIR) region. R480 is the reflectance in the band of 480nm affected by both Carotenoids and Chlorophyll. R678 is the reflectance in the band of the red region Chlorophyll absorption maximum.