Suitability of selected Sri Lankan weeds for the formulation of organic liquid fertilizers

Tithonia diversifolia, Sphagneticola trilobata, Mikania scandens, Lantana camara, Chromolaena odorata, Panicum maximum and Mimosa pigra are common weeds in Sri Lanka. This study was aimed to assess the nutrient release potential and the weight loss dynamics during leaching of the above weeds to utilize them as organic liquid fertilizers. Thirty samples from each species of oven-dried leaves (5 g) were placed separately in 1 L of distilled water. Three samples of each species were randomly collected at 1, 3, 5, 7, 14, 28, 42, 56, 70 and 84 days and the massloss, electrical conductivity (EC), pH and nutrient contents of the leachates were determined. Four fertilizers (FP1; the selected weeds Tithonia diversifolia + Mikania scandens + Chromolaena odorata (W), FP2; (W) + topsoil, FP3; (W) + topsoil + coconut husk ash and FP4; (W) + topsoil + coconut husk ash + fish waste) were formulated and based on the nutrient contents the highest nutrient containing FP3 and FP4 were applied on Basella alba. Mass-loss was higher (p<0.05) for Mikania scandens (97%) followed by Tithonia diversifolia (95.8%) and the lowest for Panicum maximum (63.7%). EC and pH of leachates were increased over the time indicating the highest in Mikania scandens (2139±4.7 μS cm) and Lantana camara (7.86±0.06) respectively, and the lowest in Panicum maximum (877±7.6 μS cm, 7.40±0.02). Nutrient contents of the leachates of Tithonia diversifolia, Mikania scandens and Chromolaena odorata were higher than those of Panicum maximum. FP4 revealed the highest nutrients and growth performances of shoot height (25.0±0.9 cm), number of leaves (12.0±0.6), leaf area (70.7±1.6 cm), plant fresh weight (56.1±1.2 g) of Basella alba. The results are suggestive of the potential of utilizing Tithonia diversifolia, Mikania scandens and Chromolaena odorata for the formulation of organic fertilizers which would in turn be a low-cost strategy for effective control of these weeds.