Application of biochar arising from gasification to rehabilitate soil of tropical secondary forest on degraded land

Biochar arising from gasification is porous (surface area 77.2m2/g), alkaline (pH 9.0), rich in nitrogen (12100ppm), phosphorus (873.4ppm), potassium (4833.3ppm) and low in its carbon to nitrogen ratio (8:1), indicating its potential use as an amendment to the soil of adinandra belukar, a form of secondary forest on degraded land. Such soil is highly compacted (surface area 4.0m2/g), acidic (pH 4.0), poor in nitrogen (1120ppm), phosphorus (3.2ppm), potassium (29.9ppm) and high in its carbon to nitrogen ratio (14:1). In this study, the forest soil was mixed with biochar at 33.3, 50.0 and 66.7% by weight, and subsequently used to cultivate water spinach (Ipomoea aquatica). After 8 weeks of cultivation, water spinach grown in the forest soil mixed with 33.3% biochar grew the tallest (193.8mm, 4 times that of pure soil), had the heaviest stem dry weight (0.483g, 10 times that of pure soil) and the largest leaf surface area (100.6cm2, 30 times that of pure soil). Compared to commercially available water spinach, it had almost the same height, heavier stem dry weight and more leaf surface area, indicating the possibility of biochar to be used as an amendment to adinandra belukar soil.