A novel portable crop environment factors stress and grain quality monitoring instrument

A novel instrument to measure photochemical reflectance index (PRI) and nitrogen reflectance index (NRI) is presented. It can measure the incident and reflected radiance of vegetation at 531 nm, 570 nm and 670 nm bands by the 6 specially designed interference filters, then PRI and NRI is derived. The PRI index can be used for the diagnosis of crop stress, such as waterlogging and drought. The NRI can be used for the diagnosis of crop nitrogen nutrition deficiency. The instruments can diagnose the plant growth status by the acquired spectral response. This optical instrument includes photoelectric detector module, signal process and A/D convert module, the data storing and transmission module and human-machine interface module. The detector is the core of the instrument which measures the spectrums at special bands. The microprocessor calculates the PRI and NRI value based on the A/D value. And the value can be displayed on the instrument's LCD, stored in the flash memory of instrument and can also be uploaded to PC through the PC's RS232 serial interface. The prototype was tested in the crop field at different view directions. The PRI and NRI data acquired by the novel instrument are compared and calibrated by an ASD FieldSpec spectrometer, which shows that this instrument is successfully developed and reliable. The winter wheat's leaf area index, water content, chlorophyll density and nitrogen content are successfully detected by the PRI and NRI instrument, this novel instrument is portable and could be fixed on the agricultural machine traveling in the field, which demonstrates the promising application of the novel portable instrument.