Bioremediation of TPS3R Compost with Various Levels of Earthworms Supplemented with Biochar on the Growth and Yield of Land Water Spinach (Ipomea Reptans Poir)

Waste is one of the most complex global issues faced by nearly every country in the world. The management of organic waste in Bali through the Reduce-Reuse-Recycle Waste Processing Facility (TPS3R) produces compost with potential use as a planting medium. However, compost derived from household waste is often contaminated with heavy metals such as arsenic (As), mercury (Hg), and manganese (Mn) that exceed the threshold limits set by SNI 19-7030-2004, thereby requiring bioremediation treatment before being agronomically utilized. This study aims to assess the effectiveness of a vermiremediation approach using earthworms combined with biochar in reducing heavy metal content in TPS3R compost and its impact on the growth and yield of water spinach (Ipomoea reptans Poir). The experiment was conducted using a factorial Completely Randomized Design (CRD) with two factors: compost sources from four TPS3R facilities (Kesiman, Jagapati, Belega, Darmasaba) and treatment combinations of earthworms (50 g, 100 g) with biochar (250 g). The results showed that the combination of earthworms and biochar significantly reduced heavy metal concentrations, such as arsenic from 836 ppm to 18.65 ppm, mercury from 22 ppm to 1.27 ppm, and manganese from 1289 ppm to 135.54 ppm. Additionally, this treatment improved plant growth and yield parameters, including plant height, number of leaves, fresh weight, and dry weight. Although the improvements were not statistically significant across treatments, they were evident in the media treated with bioremediation. These findings indicate that the combination of earthworms and biochar is a promising strategy to improve compost quality and support sustainable agriculture on drylands.