Identification of Nitrogen and Sulfur Status Utilizing Spectral Data in Corn

POTT, LUAN; ROSSO, LUIZ H. MORO; CARCIOCHI, WALTER D.; HANSEL, FERNANDO; RUIZ DÍAZ, DORIVAR; CIAMPITTI, IGNACIO A.

Congreso; ASA, CSSA and SSSA International Annual Meetings; 2019

Studying the interactive effects of nitrogen (N) and sulfur (S) nutrition on early crop growth and nutrient status is critical to better understand their impact on the final yield formation in corn (Zea Mays L.). Optical sensors such as spectrometers have been utilized to characterize spectral signature in leaf canopies in several crops. This study aimed to identify spectral wavelengths that can assist on the characterization of N and S deficiency symptoms via utilization of a hyperspectral sensor. In a greenhouse setting, four treatments (+N+S (control), -N+S, +N-S, and -N-S) were evaluated in corn. The measurements were collected at four growth and development stages: V2, V4, V6, and V8. A portable spectroradiometer capable of measuring the wavelength range of 350?1050 nm of the electromagnetic spectrum was used to collect spectral data. In the last three growth stages (V4, V6, and V8), spectral data was collected in three different leaf canopy layers (upper, medium, and lower). Fresh and dry biomass were collected, and N and S concentration were determined. The results indicated that N deficiency began as early as in the V2 growth stage, increasing the leaf reflectance in the green (centered 555 nm) and red edge (centered 715 nm) bands. However, the S deficiency was detected as early as in the V6 growth stage with the effects enlarging as the crop progresses, increasing the reflectance in both the green and red edge bands relative to the control. Nitrogen deficiency was mainly detected in the lower layer, while S in the upper. The high values for green and red edge bands correlate with gradual loss of functionality of those leaf tissues. The results indicated that identification of nutritional deficiency symptoms through spectral data could improve the diagnostic and management of N and S in corn.