Efektivitas Bakteri Bacillus subtilis dan Bahan Organik Terhadap Pertumbuhan Tanaman Kedelai (Glycine max L.) pada Interval Penyiraman yang Berbeda

Abstract

MUHAMMAD TITAN HAFIZAL. Effectiveness of Bacillus subtilis Bacteria and Organic Materials on Growth of Soybean Plants (Glycine max L.) at Different Watering Intervals (Under the guidance of MARIANI BR SEMBIRING as Chair of the Advisory Commission and NINI RAHMAWATI as Member of the Advisory Commission). Soybean cultivation in marginal lands is often constrained by drought stress. The application of Bacillus subtilis, a microbe that produces the enzyme ACC deaminase, along with organic materials such as manure and biochar, has the potential to enhance plant tolerance. This study aimed to evaluate the effects of Bacillus subtilis, organic materials, and watering intervals on the growth of soybean variety Anjasmoro under drought conditions. The experiment was conducted in a screen house at Komplek Citra Wisata, Medan Johor, using a factorial Randomized Block Design (RBD) with three replications. The first factor was microbial application (Bacillus subtilis and without microbes), the second was organic material (no organic material, cow manure, and biochar), and the third was watering interval (once every 1, 3, and 5 days). The results showed that Bacillus subtilis improved plant morphology (plant height, number of leaves, number of branches, leaf area, root length) and increased both fresh and dry weight. Biochemically, Bacillus subtilis enhanced the activity of SOD and POD enzymes but reduced yield components (number of seeds, seed weight, and number of pods). Cow manure improved plant morphology and yield, while biochar was more effective in enhancing enzyme activity. Daily watering supported optimal morphological growth, whereas watering every five days increased chlorophyll A and enzyme activity. There was a significant interaction between the three factors on plant morphology, physiology, and biochemistry. The best combination for the highest pod number was Bacillus subtilis, cow manure, and daily watering. Meanwhile, the combination of Bacillus subtilis and biochar with five-day watering was most effective in enhancing SOD enzyme activity. Keywords: Bacillus subtilis, Organic materials, Soybeans, Watering interval