ABSTRACT Hydroponic is a technique of growing plants in a soilless medium by using a sponge, rock wool, hydroton, coconut coir, and perlite as an alternative for crop production systems. Recently, biochar has been reported to be a potential substrate for hydroponic cultivation techniques due to its physicochemical properties which can help increase vegetable production. A greenhouse study was conducted to investigate the effect of biochar as hydroponic substrate on the growth, colour and nutritional content of red lettuce (Lactuca sativa L.). This study utilized the nutrient film technique (NFT) hydroponic system and was conducted using a randomized complete block design with five treatments, including T1 (hydroton only), T2 (perlite only), T3 (palm kernel biochar), T4 (palm kernel biochar + hydroton), and T5 (palm kernel biochar + perlite). Data analysis revealed the treatment, which consists of both palm kernel biochar and hydroton (T4) resulted in a significant increase in plant growth and yielded the highest plant height (19.86 cm), leaf width (14.16 cm), plant fresh weight (68.19 g), and dry weight (8.29 g). The leaves nutrient content (N, P, K, Mg, Ca) of red lettuce grown in palm kernel biochar and hydroton (T4) substrates suggested the presence of optimal growth conditions for ensuring optimum yield with high quality. The application of palm kernel biochar and hydroton (T4) as substrate also showed a higher lightness value (L* = 66.67). Besides, the methanolic leaf extracts from the red lettuce grown in palm kernel biochar and hydroton (T4) showed the highest bioactive metabolite content. In addition, the application of palm kernel biochar (T3) as a hydroponic substrate decreased the algal density in the nutrient solution. In conclusion, the combination of palm kernel biochar and hydroton as a substrate was observed to be the best in enhancing the growth performance, colour, and nutritional content of red lettuce (Lactuca sativa L.), and it is therefore recommended to be used as the growth substrate in the NFT system.

ABSTRACT Metal contamination problems have become common everywhere with several known cases of metal toxicity in the agriculture sector. Metals including copper (Cu) are important to plant metabolism in trace amounts; however, excessive amounts can cause toxicity to the plants. The biochars have potential to absorb these trace elements in soil. A study was conducted to determine the characteristics and potential of different plant-based biochars to control Cu uptake and influence on the growth of maize (Zea mays L.). Five biochars from different agricultural waste materials, such as rice husk (RH1 and RH2), empty fruit bunches (EFB1 and EFB2) and oil palm kernel (OPK), were selected in the study. Each biochar was applied at 20 t·ha-1 on Cu contaminated soil, and maize was grown for 56 days in pots with 10 kg of acidic soil. The rice husk biochar (RH1) with a substantial number of heterogenic functional groups (alcohols and phenols, carboxylic acids and derivatives, amines, saline, alkynes) on its surface and more porous structure was able to retain more nutrients. It also give the best results in terms of reducing the Cu concentrations (1.61 mg-kg-1) in plants and plant uptake (10.15 µg·pot-1). Other than that, the highest plant growth parameters were also perceived in rice husk biochar applications. Hence, RH1 biochar had the most promising results in terms of controlling the plants Cu uptake and improved maize plant growth.