## 3 Results and Discussions
### Early Growth Stage
The changes in the aluminum level, which is a potentially toxic constituent for crop production and a consideration in this study, were extremely modest, with a statistically insignificant relationship between individual treated and control plants (\(p>0.05\)). In general, aluminum is typically found as a mineral in the soil, and in strongly acidic soil, especially at pH values lower than 4.3, it will severely impede the physiological and biochemical processes of plants [40]. Consequently, their productivity will be impeded due to its excessive solubilization and the enhanced presence of trivalent aluminum (Al\({}^{3+}\)), which is known to be the most toxic form [40; 41]. Due to the alkalinity of P-BC-LDHs (Table 1), the application of P-BC-LDHs could compensate for the acidic growing media used, which greatly assisted the amelioration of aluminum phytotoxicity. In this study, the pH measurements of each substrate were performed after 21 days. The effectiveness of these materials in improving the pH of all growing media was demonstrated, with values ranging from 4.7 to 5.2, which was comparable to those without amendment (4.4). Furthermore, it has been proposed that young seedlings are more prone to aluminum stress than older plants [42]. Therefore, the lettuce observed in the present study did not demonstrate any signs of toxicity even at high applied concentrations of P-BC-LDHs, which was inconsistent with their interaction with seed germination. Notably, in addition to being a good source of nutrients, its excellent characteristics, including high pH, water retention, and CEC (Table 1) values, could partly account for the  
Figure 4: Effect of P-BC-LDHs at different dosages on growth parameters and the elemental composition of lettuce from early plant growth experiments. **(a)** Shoot and root length, **(b)** fresh and dry weight, and **(c)** elemental analysis. Different letters indicate statistically significant differences. NS indicates no significance. observed growth stimulation in lettuce. There were correlated consequences of increasing pH in the P-BC-LDH-treated growing media, where microorganism activity and nutrient availability were consecutively promoted in addition to aluminum tolerance, and therefore were beneficial to plant growth [43; 44]. The biochar used in this study exhibited well developed porosity and a large surface area, and as such, there were many advantages in the addition of P-BC-LDHs in terms of the alteration of physical properties of the substrate, such as water storage capacity, penetration resistance, and bulk density. This, in turn, encouraged water and nutrient retention and minimized nutrient leaching, which indirectly complemented lettuce development [45; 46]. In addition, it has been previously asserted that the high CEC of biochar could be another reason for improving phosphorus bioavailability and uptake [47]. Consequently, it is conceivable that the application of this spent adsorbent to agricultural growing media is highly successful in facilitating horticultural plant conditions when attempting to recycle it as a fertilizer. The recommended application amount of P-BC-LDHs is 2.5% (_w/w_). The differences between treatment and control lettuce crops are illustrated in Figure 3b.