Key findings:

The study found that the best results for growing mint plants hydroponically were achieved with the combination of 2 aerators and rockwool planting media. This combination was comparable to using 2 aerators with cocopeat + rice husk charcoal, and 1 aerator with either rockwool or cocopeat + rice husk charcoal.

What is known and what is new?

It is known that mint plants produce essential oils used in various industries, and hydroponic cultivation can help maintain their quality and quantity. This study introduces the new finding that the combination of aeration and specific planting media significantly impacts mint plant growth. Specifically, using 2 aerators with rockwool or cocopeat + rice husk charcoal planting media provides optimal results, offering new insights into effective hydroponic methods for mint cultivation.

What is the implication, and what should change now?

The implication of this study is that using an aeration system with 2 aerators and rockwool or cocopeat + rice husk charcoal planting media can significantly enhance the growth and quality of mint plants in hydroponic systems. As a result, hydroponic mint growers should consider implementing these specific combinations to optimize their crop yields and quality.

The mint plant is one of the plants that produce essential oil called candy oil or peppermint oil which has a distinctive cool and refreshing taste. This essential oil is widely used as a raw material for the food, beverage, pharmaceutical and cosmetic industries. The industrial demand for the products produced by this plant is very large, but it is not in line with the production of mint in Indonesia. According to Trisilawati, Pribadi, Rizal, and Suhirman (2020) [1] the imports for industrial sector in Indonesia reached 76.10 tons/year. Based on the needs of mint plant products and their use as medicinal plants, it is necessary to do floating raft hydroponic cultivation in order to better maintain the quality and quantity of mint plants.

The mint plant is one of the plants that produce essential oil called candy oil or peppermint oil which has a distinctive cool and refreshing taste. This essential oil is widely used as a raw material for the food, beverage, pharmaceutical and cosmetic industries. The industrial demand for the products produced by this plant is very large, but it is not in line with the production of mint in Indonesia. According to Trisilawati, Pribadi, Rizal, and Suhirman (2020) [1] the imports for industrial sector in Indonesia reached 76.10 tons/year. Based on the needs of mint plant products and their use as medicinal plants, it is necessary to do floating raft hydroponic cultivation in order to better maintain the quality and quantity of mint plants.

The planting media factor must also be considered in this cultivation because it plays a role in storing nutrients and as a support for plants. The planting medium that is often used in hydroponic cultivation is rockwool planting media, but this planting medium is not an organic growing medium so it cannot add plant nutrition, it is less environmentally friendly which can leave chemical residues for plants and the environment, the price is relatively expensive, and it is imported. Alternative planting media that can be used include cocopeat planting media and rice rice husk charcoal, which are wastes that are easily available, relatively inexpensive, can add plant nutrition, and are environmentally friendly. Cocopeat is a planting medium that has very high water absorption, has a pH range between 5.0-6.8, and is quite stable so it is good for root growth [2]. Meanwhile, rice husk charcoal planting media has very light and coarse characteristics, so air circulation is high due to many pores, high water holding capacity, and its black color can absorb sunlight effectively, and can eliminate the effects of diseases, especially bacteria, and weeds [3]. In this regard, it is necessary to conduct research on the effect of aeration and planting media on hydroponic floating rafts on the growth and yield of mint (Mentha piperita L.).

Place and time of research

The research was conducted in Rejosopinggir Village, Tembelang District, Jombang Regency, East Java, from October 2022 to January 2023.

Tools and materials

The tools used consist of a screen house made of bamboo, insect net and UV plastic, styrofoam box (floating raft construction), aerator (0.012 MPa), net pot, tray, TDS meter, pH meter, ruler, digital scales, stationery, documentation tools, measuring cup, and yellow trap. The materials used were: mint plant seeds, rockwool planting medium, cocopeat, rice husk charcoal, AB mix nutrition, pH up, pH down, vegetable pesticides, and label paper.

Experimental design

The research was arranged in a factorial manner using a Split Plot Design in a Completely Randomized Design with the main plot being aeration (A) consisting of 3 levels namely (1) A1: non-aerator; (2) A2:1 aerators; (3) A3: 2 aerators and subplots are planting medium (M) which consists of 4 levels: (1) M1: rockwool, (2) M2: cocopeat, (3) M3: rice husk charcoal, and (4) M4: cocopeat + rice husk charcoal. Each combination was repeated 3 times so that a total of 36 experimental units were produced. The experimental unit group contained 3 samples so there were 108 plants.

1. Number of Leaves (strands)

In the variable number of mint leaves observed, there was a significant interaction between aeration and the planting medium at the age of 49 - 63 days after planting (DAP) as shown in Table 1. The average number of mint leaves was 49 - 63 DAP.

Figure 1 shows that the A3M1 combination treatment (2 aerators and rockwool) at the age of 49 - 63 DAP has the highest average number of leaves of mint plants, namely 173.78 strands, 209.78 strands and 226.44 strands. The lowest number of leaves of mint plants at the age of 49 - 63 HST was shown by the combination treatment A1M3 (without aerator and rice husk charcoal), namely 160.33 strands, 194.00 strands and 211.33 strands. Table 1 Shows that the combination treatment A3M1 (2 aerators and rockwool) at the age of 49 - 63

DAP is significantly different from the other combination treatments except for the combination treatment A3M4 (2 aerators and cocopeat + rice husk charcoal), and A2M1 (1 aerator and rockwool). There was a 7.15% increase in the number of leaves of 63 HST mint plants in the A3M1 combination treatment (2 aerators and rockwool) compared to the A1M3 combination treatment (without aerator and rice husk charcoal).

Table 1. The average number of leaves on the mint plants due to the combined treatment of aeration and planting media was 49 - 63 DAP.

Information : Numbers followed by the same letter in the same column are not significantly different based on BNJ 5%.

Figure 1 Diagram of the average number of leaves of mint plants aged 49-63 days after planting Providing aeration with aerators in floating raft hydroponics can increase dissolved oxygen in the water and make it easier for the roots to absorb nutrients so that the elements N, P, and K in the ab mix nutrient solution can affect the photosynthesis process to produce photosynthate, allowing plants to grow better and increase plant production. Oxygen in the planting media makes it easier for the roots to breathe, so the energy generated by the respiration process can be used for assimilation in the process of absorbing water and nutrients.   Kurniasih (2011) [4] said that high levels of dissolved oxygen can facilitate the respiration process of plants, allowing the roots to produce enough energy to optimally absorb nutrients. The result is faster plant growth and high productivity and quality. According to Charitsabita et.al.et.al. (2019) [5], the more nutrients that can be absorbed by the plants, the more the production of the plants can be increased because these nutrients can be used by the plants for photosynthesis. Soeseno (1991) [6] said that good root growth and wider distribution makes the plants capable to absorb available nutrients, especially. In which plays a very important role in leaf growth so that it can help increase the number of leaves. Mint plants are plants whose economic value lies in the leaves, which are vegetative organs. Therefore, if the photosynthate produced in the photosynthesis process is high, the production yield will be high.

1. Fresh Weight per Plant (grams)

The results of the average fresh weight per plant in Table 2. show that the combination of aeration and planting media treatment occurs in interaction. The combination treatment A3M1 (2 aerators and rockwool planting media) was significantly different from all combination treatments, except for the combination treatment A3M4 (2 aerators and cocopeat + rice husk charcoal), A2M1 (1 aerator and rockwool) and A2M4 (1 aerator and cocopeat + rice husk charcoal).

due to the combination treatment aeration and planting media at 63 DAP.

Information : Numbers followed by the same letter in the same column are not significantly different based on BNJ 5%.

Figure 2. Diagram of average fresh weight per mint plant aged 63 DAP

Figure 2 shows that the combination treatment A3M1 (2 aerators and rockwool) has the heaviest average wet weight per plant than the other combination treatments, while the lowest average fresh weight per plant is found in the combination treatment A1M3 (without aerators and rice husk charcoal). The combination treatment A3M1 (2 aerators and rockwool) has the heaviest average wet weight per plant as shown in Table 2, which is 104.31 cm, while the combination treatment A1M3 (without aerators and rice husk charcoal) has the lowest average fresh weight per plant with a value of 37.88 grams.

The high fresh weight per plant is thought to be due to stimulated root respiration so that nutrient uptake is not inhibited by oxygen enrichment. The planting medium used also has good porosity, so it can store nutrients to meet the nutrient needs of plants, and has good aeration to make it easier for plants to exchange air. As stated by Lahadassy et al. (2007) [7], to achieve optimal plant wet weight, plants really need enough dissolved oxygen to properly and thoroughly distribute nutrients, which results in leaf cell enlargement and increased fresh weight of the obtained crown.

1. Root Fresh Weight (grams)

The observation variable of fresh weight of mint plant roots showed no interaction in the combined treatment of aeration and planting media. However, each individual treatment showed significant results as shown in Table 3.

Table 3. The average fresh root weight of plants treated of aeration and planting media at 63 DAP.

Information : Numbers followed by the same letter in the same column are not significantly different based on BNJ 5%.

Table 3 shows that the heaviest fresh weight of plant roots is in the single aeration treatment A3 (2 aerators) with a weight of 12.69 grams. This is significantly different from the other treatments. The single treatment of media M1 (rockwool) had the heaviest fresh root weight of 12.63 grams and was significantly different from the single treatments of other media, except for the treatment of media M4 (cocopeat + rice husk charcoal).

Aeration can increase dissolved oxygen. This makes it easier for plants to absorb nutrients that can affect plant growth and development. The yield of crop production will increase if the growth and development of plants are good. Optimal oxygen availability in the rooting media causes the roots to not experience decay so that the absorption of nutrients by plants can occur optimally because the roots are easy to respire [8]. Respiration is the process of converting stored energy into usable energy. The sugar that is produced by photosynthesis will react with oxygen to produce CO2, energy, and water. The energy produced is then used for various growth activities, one of which is the process of photosynthesis. Oxygen is required in this reaction, therefore if the plant lacks oxygen, its respiration will be disrupted [9].

Rockwool planting media can hold up to 14 times the water capacity, can optimize the role of fertilizers, and can support plant growth because the cavity is easily passed by roots and can be used repeatedly [10]. In the meantime, the mixed planting media of cocopeat and rice husk charcoal, which is an organic planting media, has aeration that is as good as that of rockwool planting media and has good porosity that can increase the storage capacity of nutrient solutions in plants, so the mixed planting media of cocopeat and rice husk charcoal can be used as an alternative to rockwool planting media. Organic planting media combined with cocopeat and rice husk charcoal can support the absorption and penetration of roots in absorbing nutrients compared to the provision of organic media independently because each organic planting media has advantages and disadvantages. The shortcomings of each media can be minimized by combining them [11]. Cocopeat can store water containing nutrients in its pores so that the frequency of fertilization can be reduced, high water absorption, contains nutrients from nature that plants need and supports rapid root growth so it is good for seedlings [12]. The rice husk charcoal planting media is porous and contains good macro and microelements. Rice husk charcoal has a chemical content of SiO2 of as much as 52% and C of as much as 31%. In small amounts, the chemical content is Fe₂O₃, MnO, Cu, CaO, MgO, and K₂O [13].

1. Test for Vitamin C Content

Tests were performed on 9 samples from the 3 best treatment combinations, each with 3 replicates. The test results of the vitamin C content of mint plants due to the combination of aeration and planting media are shown in Table 4.

The results of the vitamin C content test in Table 4 show that the highest vitamin C content is found in the A2M1 treatment combination (1 aerator and rockwool planting media) with an average vitamin C content value of 20.62 Mg/100 ml. While the average value of vitamin C content in the treatment combination A3M1 was 15.73 Mg/100 ml and the treatment combination A3M4 18.85 Mg/100 ml.

Table 4. Test results of vitamin C content of mint plants treated with a combination of aeration and planting media at 63 DAP.

Information: A2 (1 aerator); A3 (2 aerators); M1 (rockwool); M4 (cocopeat + rice rusk charcoal); (1) = sample 1; (2) = sample 2; (3) = sample 3.

The highest vitamin C test results were shown by the treatment combination of 1 aerator and rockwool media and the lowest results were shown by 2 aerators and rockwool media. It is suspected that post-harvest factors can affect the vitamin content of the plant. As stated by Lee and Kader (2000) [14], there are many factors that can affect the vitamin C content of plants, such as maturity at harvest, harvesting methods and post-harvest handling conditions, as well as processing methods and cooking procedures that can result in vitamin C loss. Fresh fruits and vegetables as living tissues are subject to continuous changes after harvest. Fresh fruits and vegetables, as living tissues, can undergo continuous changes after harvest. These changes cannot be controlled within certain limits by using various postharvest procedures. In general, fruits and vegetables that are freshly harvested contain more vitamin C than those that are stored.

The aeration treatment with 2 aerators and rockwool planting media gave the best results and was not significantly different from the treatment with 2 aerators and cocopeat + rice husk charcoal planting media for the observation variables of number of leaves and fresh weight per plant. The root fresh weight observation variable did not interact between aeration treatment and planting media, the best results were shown by the aeration treatment of 2 aerators and rockwool planting media which were not significantly different from cocopeat + rice husk charcoal planting media.

ACKNOWLEDGEMENT

The author would like to thank Dr. Dra. Sutini, M.Pd. and Ir. Rr. Djarwatiningsih P.S., M.P. as well as agrotechnology friends, faculty of agriculture UPN "Veteran" East Java.

Conflict of Interest:

The authors declare that they have no conflict of interest.

Funding: No funding sources 

Ethical approval: The study was approved by the Institutional Ethics Committee of Universitas Negeri Makassar

1. Trisilawati, Oktivia, et al. "PENGARUH PEMUPUKAN N, P DAN K TERHADAP PRODUKTIVITAS DAN MUTU MINYAK Mentha arvensis." Jurnal Agronida 6.2 (2020).  https://pdfs.semanticscholar.org/8f73/58a4b6f183df4a9c56a68da7fc865903447a.pdf

2. Laksono, Rommy Andhika, and Darso Sugiono. "Karakteristik Agronomis Tanaman Kailan (Brassica oleraceae L. var. acephala DC.) Kultivar Full White 921 Akibat Jenis Media Tanam Organik dan Nilai EC (Electrical Conductivity) pada Hidroponik Sistem Wick." Jurnal Agrotek Indonesia (Indonesian Journal of Agrotech) 2.1 (2017). http://journal.unsika.ac.id/index.php/agrotek/article/download/715/626

3. Safii, I. "Kombinasi Nutrisi Hidroponik dan Komposisi Media Tanam terhadap Pertumbuhan dan Hasil Tanaman Selada Merah (Lactuca Sativa Var. Lollorosa) Dengan Sistem Hidroponik Sumbu." Skripsi Universitas Muhammadiyah (2020).

4. Kurniasih, Anindya. "Pengaruh Penggunaan Aerator Pada Hidroponik Sistem Rakit Apung (Floating Hidroponic System/Fhs) Dan Kultur Air (Deep Flow Technique/Dft) Terhadap Pertumbuhan Dan Hasil Beberapa Tanaman Sayuran." (2011). https://digilib.uns.ac.id/dokumen/detail/17756

5. Charitsabita, Rona, Endang Dwi Purbajanti, and Didik Wisnu Widjajanto. "Respon Pertumbuhan dan Hasil Tanaman Pakcoy (Brassica rapa L.) secara Hidroponik dengan Berbegai Jenis Media Tanam dan Aerasi Berbeda." Jurnal Pertanian Tropik 6.2 (2019): 270-278. 

6. Soeseno, S. (1991). Bertanam Secara Hidroponik. Gramedia. Jakarta

7. Lahadassy, J., A. M. Mulyati, and A. H. Sanaba. "Pengaruh konsentrasi pupuk organik padat daun gamal terhadap tanaman sawi." Jurnal Agrisistem 3.6 (2007): 51-55. 

8. Ningsih, Rinda Ika Wahyu, and Nurul Aini. "Pengaruh durasi penggunaan aerator dan pengaplikasian PGPR (Plant Growth Promoting Rhizobacteria) terhadap pertumbuhan dan hasil tanaman selada (Lactuca sativa L.) pada hidroponik sistem rakit apung." Plantropica: Journal of Agricultural Science 6.2 (2021): 106-114. https://jpt.ub.ac.id/index.php/jpt/article/view/245

9. Vidianto, Daviv Zali, Siti Fatimah, and Catur Wasonowati. "Penerapan panjang talang dan jarak tanam dengan sistem hidroponik NFT (nutrient film technique) pada tanaman kailan (Brassica oleraceae var. alboglabra)." Agrovigor: Jurnal Agroekoteknologi 6.2 (2013): 128-135. DOI: https://doi.org/10.21107/agrovigor.v6i2.1488

10. Sari, Kun Rawan, Jamzuri Hadie, and Chatimatun Nisa. "Pengaruh Media Tanam pada Berbagai Konsentrasi Nutrisi terhadap Pertumbuhan dan Hasil Seledri dengan Sistem Tanam Hidroponik NFT: Influence of Planting Medium on Different Nutrient Concentration to the Growth and Yield of Celery with the Nutrient Film Technique Hydroponic Cultivation System." Daun: Jurnal Ilmiah Pertanian dan Kehutanan 3.1 (2016): 7-14. DOI: https://doi.org/10.33084/daun.v3i1.155

11. Miranda, S. (2017). Efektivitas Cocopeat dan Arang Sekam dalam Mensubstitusi Media Tanam Rockwool pada Tanaman Mint Secara Hidroponik Dengan Sistem Sumbu. Agroekoteknologi, 3(1), 1–8.

12. Nurifah, Gemah, and Resti Fajarfika. "Pengaruh Media Tanam pada Hidroponik terhadap Pertumbuhan dan Hasil Kailan (Brassica Oleracea L.)." Jagros: Jurnal Agroteknologi dan Sains (Journal of Agrotechnology Science) 4.2 (2020): 281-291. https://journal.uniga.ac.id/index.php/JPP/article/viewFile/925/774

13. Wijaya, Rizza, Budi Hariono, and Tri Wahyu Saputra. "Pengaruh kadar nutrisi dan media tanam terhadap pertumbuhan bayam merah (Alternanthera amoena voss) sistem hidroponik." Jurnal Ilmiah Inovasi 20.1 (2020). https://publikasi.polije.ac.id/index.php/jii/article/view/1929

14. Lee, Seung K., and Adel A. Kader. "Preharvest and postharvest factors influencing vitamin C content of horticultural crops." Postharvest biology and technology 20.3 (2000): 207-220. https://doi.org/10.1016/S0925-5214(00)00133-2