[New method and instrument to diagnose crop growth status in greenhouse based on spectroscopy]

Spectral reflectance of cucumber leaves in greenhouse was measured using an ASD FieldSpec Pro VNIR spectrometer with natural illumination. Two sensitive wavelengths, 527 nm and 762 nm, were selected to evaluate the nitrogen content of the cucumber leaves. A model was established and validated using normal difference color index(NDCI) with the correlation coefficient of 0.881. Based on the above efforts, a handheld spectral instrument was developed to diagnose the growth status of the crop in greenhouse using fiber optics. The instrument was mainly composed of four parts: reflected light acquisition system, light intensity measurement unit, signal conditioning unit, and data acquisition system. The sunlight reflected by the crop was transmitted by the fiber, and passed through the light filter to obtain light at the sensitive wavelengths. Finally it was transformed into electronic signal by the photoelectric transistor, and was used to diagnose the growth status of the crop according to the evaluation model. The result showed that the developed instrument was practical.