<![CDATA[Nutrient concentration determines the balance between nutrient availability and osmotic stress in hydroponic lettuce production. This study evaluated the growth and yield response of red lettuce to different AB Mix concentrations in a floating-raft hydroponic system. The experiment was conducted at the Greenhouse of Universitas Bosowa from March to May 2025 using a randomized block design with four treatments: P1 (560 ppm), P2 (653 ppm), P3 (746 ppm), and P4 (840 ppm), each replicated three times. A total of 240 plants were used and 96 plants were observed. Plant height, leaf number, root volume, leaf area, and fresh weight were measured. Data were analyzed using analysis of variance followed by the honestly significant difference test at 5% when treatment effects were significant. P4 produced the highest plant height (18.30 cm), leaf number (9.37 leaves), root volume (9.51 mL), and leaf area (119.22 cm²). P3 produced the numerically highest fresh weight (30.00 g), but the source data stated that fresh-weight differences were not significant. Thus, 840 ppm was the best tested concentration for vegetative growth, whereas 746 ppm showed the highest numerical fresh weight. The interval of 746–840 ppm should be regarded as a promising tested range rather than a mathematically optimized concentration. Konsentrasi nutrisi menentukan keseimbangan antara ketersediaan hara dan tekanan osmotik pada produksi selada secara hidroponik. Penelitian ini mengevaluasi respons pertumbuhan dan hasil selada merah terhadap konsentrasi AB Mix pada sistem hidroponik rakit apung. Penelitian dilaksanakan di Greenhouse Universitas Bosowa pada Maret–Mei 2025 menggunakan rancangan acak kelompok dengan empat perlakuan, yaitu P1 (560 ppm), P2 (653 ppm), P3 (746 ppm), dan P4 (840 ppm), masing-masing diulang tiga kali. Sebanyak 240 tanaman digunakan dan 96 tanaman diamati. Parameter meliputi tinggi tanaman, jumlah daun, volume akar, luas daun, dan bobot basah. Data dianalisis menggunakan analisis ragam dan dilanjutkan uji beda nyata jujur taraf 5% apabila perlakuan berpengaruh nyata. P4 menghasilkan tinggi tanaman 18,30 cm, jumlah daun 9,37 helai, volume akar 9,51 mL, dan luas daun 119,22 cm², yang merupakan nilai tertinggi pada parameter tersebut. P3 menghasilkan bobot basah numerik tertinggi sebesar 30,00 g, tetapi data sumber menyatakan bahwa perbedaan bobot basah tidak nyata. Dengan demikian, 840 ppm merupakan konsentrasi terbaik yang diuji untuk pertumbuhan vegetatif, sedangkan 746 ppm memberikan bobot basah numerik tertinggi. Kisaran 746–840 ppm lebih tepat dinyatakan sebagai rentang uji yang menjanjikan, bukan konsentrasi optimum matematis.]]>
