Role of watering interval and media composition on the growth of exotic fast growing species on coal mining soil

Open mining of non-renewable energy from coal in tropical regions causes land degradation, temperature stress, water stress, high acidity, aluminum toxicity, and other poor soil characteristics. Kranji (Pongamia pinnata)) is an exotic fast-growing species whose tolerance to drought conditions and marginal soils are potential for the revegetation of degraded areas. This research aimed to analyze the effect of coal mining media, watering interval, and their interaction on the growth of kranji seedlings. This research was conducted in October 2015 with a 4-months observations period. The research used a completely randomized factorial design comprising soil media and watering interval. Three soil media treatments comprising secondary forest soil, disposal, and overburden in coal mining media were performed in PT Berau Coal, Berau, East Kalimantan. The watering interval was every 3 and 7 days. Organic pot made from leaf litter was used as basic treatment in this research, and kranji seedlings were obtained from Banyuwangi Protected Forest. The total chlorophyll, height, diameter, shoot dry weight, root dry weight, and top/root ratio parameters were measured. Soil media and watering interval significantly affected the height, shoot dry weight, and top/root ratio of kranji seedlings. The interaction between watering interval and soil media was not significant for all parameters. P. pinnata was tolerance to drought and poor nutrient of post-coal mining soil. Exotic fast-growing species of P. pinnata is suitable for the rehabilitation of post-coal mining land in tropical regions.