Photoacoustic Technique Applied to the Assessment of the Dosage of a NPK Fertilizer in Maize (Zea mays L.)

The photosynthetic activity of maize plants (Zea mays L.) grown at different concentrations of a synthetic NPK fertilizer was evaluated and compared to explore an effective dosage criterium. The plants were grown under greenhouse conditions in a sterile medium to ensure controlled provision of nutrients. The Stomatal Density (SD) and Stomatal Index (SI) of the plants were estimated through micrograph analysis; while the rate of oxygen evolution, the absorption spectral curves, and the thermal diffusivity of the plant leaves were measured using the Photoacoustic Technique. The results regarding photosynthetic activity and thermal diffusivity indicated an oscillatory pattern of behavior during the growth period, and the characteristics of these oscillations were affected by the application of the NPK fertilizer. The photoacoustic spectroscopy analysis served to show that the treatment with the highest dosage of NPK fertilizer caused a decrease in the absorption of the chlorophyll a and b. Based on the results, the proposed methodology and used technique could have practicality in monitoring quantifiable variables to evaluate the influence that a fertilizer has on plants such as maize, which allows the determination of appropriate dosage.