VERMICOMPOSTING AS A DETOXIFICATION AND NUTRIENT-RECOVERY STRATEGY FOR PARTHENIUM HYSTEROPHORUS L.

Abstract

Parthenium hysterophorus L. is a noxious weed whose biomass contains phytotoxic compounds and should not be recycled into agriculture without stabilization. This study evaluated appropriate composting methods for converting Parthenium biomass into a mature, nutrient-rich, and crop-safe amendment. Eight treatments were tested in a completely randomized pot experiment with three replications: Parthenium combined with cow dung at 1:1 or 2:1 (w/w), the same mixtures with Eisenia fetida earthworms, and corresponding Parthenium:farm-waste:cow-dung mixtures at 1:1:1 or 2:1:1 (w/w), with and without earthworms. Each tub received 6 kg dry substrate, moisture was maintained at approximately 60–70%, and compost was harvested after 90–105 days. Maturity was assessed through pH, electrical conductivity, organic carbon, total N, P₂O₅, K₂O, C:N ratio, and recovery. A green-gram bioassay tested residual phytotoxicity. Mature composts had near-neutral pH (7.236–7.621), EC of 1.300–1.463 dS m⁻¹, C:N ratios of 9.550–16.287, total N of 1.720–2.420%, P₂O₅ of 0.766–0.865%, and K₂O of 1.250–1.500%. Earthworm treatments generally accelerated carbon loss, narrowed C:N ratio, increased recovery, and improved green-gram establishment. Treatment T7, Parthenium + farm waste + cow dung at 1:1:1 (w/w) with earthworms, gave 70.023% recovery, 13.057 C:N ratio, 0.865% P₂O₅, 100% green-gram germination by 5 days, 11.51 cm shoot length, 11.20 cm root length, and vigour index 2271. T4, Parthenium + cow dung at 2:1 with earthworms, produced the highest mature N and K concentrations and the lowest C:N ratio in the non-farm-waste group. The results show that balanced co-substrates with earthworms provide the most reliable combination of maturity, nutrient recovery, and crop safety, and that crop bioassay should accompany chemical compost testing before field use.