Rocking Radishes: The Effect of 8 kHz Sound on Biomass Accumulation in Raphanus sativus

I chose to explore sonic agriculture because of my interest in both music and nature. Sonic agriculture is the concept that sound waves can influence plant growth. I was fascinated by the idea that sound could affect biological systems, and I wanted to understand whether different types of sound could produce measurable changes in plants.

I reviewed existing research and I noticed that most studies focused on low-frequency sound (0.1–5 kHz) and often reported positive effects on growth. However, very little research examined higher frequencies. This led me to an important question: do these effects continue at higher frequencies, or is there a threshold where sound no longer has an impact?

To investigate this, I designed an experiment testing how 8 kHz sound at different sound pressure levels affects biomass accumulation in radish plants. Radishes were chosen due to their rapid growth cycle, allowing for controlled data collection over a short period.

This research is important because for sonic agriculture to be practical, it must be both effective and efficient. Therefore, identifying conditions that do not produce measurable benefits is essential for real world application. My results showed that 8 kHz sound did not significantly affect plant biomass, suggesting that plant responses to sound may depend strongly on frequency.

By exploring the influence of sound on biology, this project helps refine the limits of sonic agriculture and supports the development of more targeted, sustainable agricultural practices.

I began this project by reviewing scientific studies on how sound affects plant growth. I focused on peer-reviewed journal articles to make sure the information was reliable and relevant. This led me to identify a gap in research on higher-frequency sound.

To fill this gap, I designed an experiment using radish plants because they grow quickly and have quick economic turnaround for farmers. A total of 40 plants were grown under identical conditions and divided into four groups of 10. One group was a control (no sound), while the other three were exposed to 8 kHz sound at different sound pressure levels: 55 dB, 65 dB, and 75 dB.

To make sure the experiment was fair, all plants received the same soil and amounts of light and water, and were grown in the same environment. I built sound-dampening boxes to prevent sound from one group affecting another. Each group was exposed to sound for one hour per day over a 26-day period.

Throughout the experiment, I monitored plant growth and recorded observations. At the end of the 26 days, all plants were harvested and dried until their mass no longer changed. This allowed me to measure dry biomass, which removes the confounding effects of water and provides a consistent way to compare growth. Each plant was measured individually, and the data from all 40 plants was collected and analyzed to determine whether sound had a significant effect on growth.

At the end of the 26-day growth period, all 40 radish plants were successfully harvested and analyzed for dry biomass. The average dry biomass for each group was very similar. Plants exposed to 55 dB had a mean mass of 0.224 g, 65 dB had 0.251 g, and 75 dB had 0.246 g. The control group had a mean of 0.246 g. Although there were small differences between group averages, there was also a high level of variation within each group.

The bar graph shown summarizes these results, with error bars representing standard deviation. The overlap between groups demonstrates that any differences in mean biomass are not meaningful.

To confirm the interpretation indicated by the bar graph, I used a one-way ANOVA. This test was selected because it allows for comparison of more than two independent group means at once while avoiding the increased risk of Type I error that would result from conducting multiple t-tests. ANOVA works by separating the total variation in the data into two components: variation between groups (which could be caused by the treatment) and variation within groups (natural differences between individual plants). By comparing these two sources of variation, it determines whether the treatment effect is large enough to stand out from random variability.

The analysis showed no statistically significant difference between groups (F(3, 36) = 0.236, p = 0.871). Since the p-value is much greater than 0.05, the null hypothesis cannot be rejected. This indicates that the variation between group means was very small relative to the variation within each group. Because each group had an equal sample size (n = 10), the ANOVA remains a reliable method for detecting differences even without formal assumption testing.

I also calculated the effect size to evaluate how much influence the sound pressure levels had on growth. The effect size (η² = 0.019) was very small, meaning that sound pressure level accounted for only about 1.9% of the variation in plant growth. The majority of the variation observed was due to natural differences between individual plants rather than the sound treatment. In other words, most of the variation occurred within groups, not between them.

In addition to biomass, I monitored general plant development throughout the experiment. I recorded characteristics such as leaf number, plant height, and overall structure. However, these did not show any consistent relationship with sound exposure. Differences in these traits appeared randomly across all groups.

Overall, these results indicate that exposure to 8 kHz sound at the tested sound pressure levels did not significantly affect biomass accumulation in radish plants under these conditions.

The results of this study showed that 8 kHz acoustic stimulation, across all tested sound pressure levels, did not produce a statistically significant effect on the dry biomass of Raphanus sativus. This indicates that, under these conditions, high-frequency sound neither enhanced nor reduced plant growth. Importantly, there was also no evidence of harm, as treated plants showed no consistent negative effects compared to the control.

A key conclusion is that plant responses to sound are likely frequency-dependent. While previous research has demonstrated positive effects at lower frequencies (0.1–5 kHz), these results show that those effects do not extend to 8 kHz. This supports the idea of a functional threshold beyond which sound no longer triggers meaningful biological responses.

These findings highlight the value of null results. Identifying conditions that do not produce measurable effects helps refine scientific understanding and prevents inefficient use of resources. In the context of sonic agriculture, this means that not all sound-based approaches are equally effective, and careful optimization is necessary.

From an applied perspective, this work supports the development of more precise and efficient agricultural strategies. By eliminating ineffective sound treatments, future research can focus on conditions that may enhance growth. This targeted approach could contribute to more sustainable farming practices, including reducing reliance on chemical fertilizers and pesticides.

Overall, this study helps define the limits of sonic agriculture and provides clear direction for future research and application.

Future research could expand on this study by testing a wider range of frequencies above and below 8 kHz to better identify where plant responses begin and end. Increasing the sample size would improve statistical sensitivity and help detect smaller effects. Measuring additional outcomes, such as nutrient content or flavonoid levels, could reveal biological changes not reflected in biomass. Conducting similar experiments in greenhouse or field conditions would also improve real-world applicability. These next steps would help further define how sound can be used effectively and efficiently in agricultural systems.

I would like to thank my parents for their support throughout this project. My mom assisted me with setting up experimental materials and helped purchase the equipment needed to carry out the study. Their support made it possible for me to complete the experimental setup and maintain consistency throughout the project.

References

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