The Effect of Harmonic Frequency and Sound Intensity on the Opening of Stomata, Growth and Yield of Soybean (Glycine max (L.) Merrill)

Abstract

Seventy percent of Indonesia’s soybean demands and consumption are met from imports, and therefore, it is necessary to increase its local production. This study assessed the effects of harmonic frequency and sound intensity levels on the opening of stomata, the growth and yield of soybean. Experiments were conducted in a split plot design, with frequency harmony (F4: 4 kHz, F8: 8 kHz, F12: 12 kHz) being the main plots and sound intensity (A50: 50 decibels (dB), A80: 80 dB and A110: 110 dB) used as sub plots. The results showed there was no significant effect of frequency and intensity on the measured response (stomata opening). However, if they were compared with those at 0 frequency and 0 intensity, the stomata openings were significantly different based on t-test at p = 0.05. This means the opening of stomata was affected by resonance. In general, the sound level pressure attempted in the range of 50-110 dB had no effect on the width of stomata opening, but it affected to the growth and yield of soybean. The best growth of the leaf area and relative growth rate were in the presence of sound waves at a frequency of 4 kHz. Likewise, the best result of the average fresh weight of seed, dry weight of seed and harvest index were at a frequency of 4 kHz sound waves. The leaf area, seeds fresh and dry weight, and harvest index were also significantly highest at sound intensity of 50 dB. Therefore, to improve the productivity Istirochah Pujiwati, Nurul Aini, Setyawan P. Sakti and Bambang Guritno 964 Pertanika J. Trop. Agric. Sc. 41 (3): 963 - 974 (2018) of soybean plants, exposure at a frequency of 4 kHz and sound intensity of 50 dB, followed by an application of leaf fertiliser according to recommended dosage is the best combination of treatment in growing soybean in Indonesia.