Lettuce (Lactuca sativa L.) is a vegetable whose commercial value is quite good and the demand for lettuce has increased, along with the narrowing of cultivated land. The solution is hydroponic cultivation with the NFT system. Dependence on imported rockwool planting media on hydroponic cultivation often becomes a constraint for availability when needed and is expensive. Therefore it is necessary to study the feasibility of using local planting media, such as: coconut fiber and rice husk charcoal as a replacement media for rockwool and whether the increased concentration of nutrients given to the planting media affects the rate of plant growth and lettuce yield. The purpose of this study was to determine the interaction between planting media and nutrient concentrations (AB Mix) on the growth and development rate of plants, as well as the yield of lettuce hydroponically with the NFT system.

The research was arranged in factorial (two factors) using a Split Plot Design. The first factor as the main plot of AB Mix nutritional concentration (K)  consisting of 3 levels (600 ppm, 900 ppm and 1,200 ppm), while the second factor as subplot is a planting media (M) consisting of 3 levels of treatment, namely: Rockwool, Rice Husk Charcoal and Coconut Fiber. The data obtained were analyzed using analysis of variance (ANOVA), if there was a significant influence followed by a 5% BNJ test.

The results showed that there was a significantly interaction between the treatment combination of planting media and AB Mix concentration on fresh weight of lettuce. The combination treatment of rice husk charcoal planting media and AB Mix concentration of 1200 ppm (M3K3) produced the best growth and increased the fresh weight of lettuce plants by 447.54% compared to the combination of rockwool media treatment and AB mix concentration of 600 ppm (M1K1). Rice Husk Charcoal planting media produced the growth rate of plant length and leaf area of ​​26% and 81.54% compared to rockwool growing media. AB Mix concentration of 1200 ppm gives the best response and increases the growth rate of plant length and lettuce leaf area respectively by 367.5% and 165% compared to the concentration of 600 ppm.