With the aid of the portable IoT system, the reading of the nutrient concentration and EC was collected periodically from the sensor nodes and a Tx LoRa transceiver through the cloud servers. The results are presented in Fig 4a, b and 4c. Soilless medium M2 and M3 showed the highest nitrogen content and significantly differed from M1, M4 and M5. However, M5 (control) performed better than M1. The high N concentration in M2 and M3 could have been due to the addition of BRH and perlite. BRH possesses a high silica concentration which makes it a good additive since it increases soil fertility. BRH also enhances nutrient retention when combined with materials like coconut coir dust
(Kulkarni et al., 2014).
Perlite increases the porosity of soilless media and helps to maintain nutrient of the media however, excessive use of perlite is discouraged because it create a rapid drainage of water, which will be harmful to plants
(Kingston et al., 2020). Soilless media M2 and M3 recorded the highest levels of phosphorus concentration, followed by M4 which was significantly different from M1 and M5. As for the potassium concentration, M2 performed best and was significantly different from the rest of the soilless media, while M1 and M3 were significantly different from M4 and M5. The highest EC levels were observed in M2 and M3 with 1.29 dS/m and 1.28 dS/m respectively, followed by M1 and M5 with 1.16 dS/m and 1.02 dS/m respectively, all of which were significantly different from M4’s 0.97 dS/m Fig 4d.
The highest plant height was recorded on soilless medium M2, followed by M3 and both were different from the rest of the soilless media as shown in Fig 5a. However, there were significant differences between M4, M1 and M5. The differences in height among growing media may be due to similar differences in their nutrient concentration. Soilless media containing BRH, due to its high silica content improves nutrient uptake, turgidity and plant structure
(Karam et al., 2021). In addition, soilless media containing burnt rice husk and perlite aid rapid plant growth which could easily be reflected in the plant canopy, plant stem and leaf number
(Awang et al., 2010). Due to its high porosity, BRH largely possesses a skeletal structure. It prevents bacterial attack, regulates the pH of soilless media and permeates oxygen throughout root zones, making it an ideal soilless medium additive.
Noticeably, the highest number of leaves was recorded in the plants grown on soilless media M2 and M3, with 43.8 and 41.8 respectively and significantly different from the remaining media treatments Fig 5b. The comparatively high number of leaves recorded from M2 and M3 could have been due to their material composition and nutrient concentration. This is in agreement with the study conducted by
Gonbad et al., (2013) who reported that a medium containing vermiculite and perlite increases the number of plant leaves and growth traits. Plants with a high concentration of P as shown in M2 and M3 produce the maximum number of leaves, especially when perlite is combined with edaphic factors like optimum moisture content, favourable pH and aeration (Kim and Li, 2016;
Salisu et al., 2013).
The leaf area of plants grown in M2 was significantly different at p<0.05 (971.37 cm2/plant) from plants grown in M1 (722.55 cm2/plant), M3 (717.23 cm2/plant), M4 (694.38 cm2/plant) and M5 (694.38 cm2/plant) Fig 5c. The nitrogen level was significantly higher in soilless medium M2 than those that were planted in other media. Leaf area is a key indicator of how efficiently nitrogen is used by plants and it has considerable impacts on growth parameters like plant height
(Hirel et al., 2001).
Fruit length, diameter and fruit weight varied significantly among the new soilless media and the CD (Fig 6a). M2 plants had longer fruits, followed by M3 and M4, all three of which were comparatively longer than M1 and M5. Similarly, fruit diameters were comparatively wider in plants grown in M2 and M3 and significantly different from plants grown in M1, M4 and M5 (Fig 6b). The results revealed that total fresh fruit weights were significantly greater in soilless media M2 and M3 and significantly different from plants grown in M1, M4 and M5. This could have been due to the soilless nutrient concentration. There is a significant and positive correlation between nutrients and fruit quality
(Sharma and Kumawat 2019).
Noticeably, CD recorded the lowest total fruit fresh weight after M1 (Fig 6c). The sweetness of the rock melon from different soilless media is presented in Fig 6d. The highest soluble solids content 18.4% was recorded in soilless medium M2 and significantly different from the rest of the soilless media. The M3 media were solids content 14.72% higher followed by M2 and is also significantly different from plants grown in M1, M4 and M5. The sweetness of the fruits was related to the soilless media, especially fruits harvested from M2 was remarkable. This could have been due to the EC levels which ranged from 0.9 dS/m to 1.5.