Utilization of Alligator Weed as Organic Liquid Fertilizer: A Comparative Study on Okra (Abelmoschus esculentus) Growth and Yield

Abstract

Alligator weed (Alternanthera philoxeroides) is a highly invasive species causing severe ecological and economic consequences by affecting water quality, hydrological flow, and the growth of native flora and fauna due to its rapid growth and dense mat formation. It thrives in both aquatic and terrestrial habitats and has become a significant ecological concern in Sri Lanka. In Trincomalee, a two-hectare farm pond in Anpuvalipuram has been infested annually, typically from November to May (up to 1.5-hectare level), disrupting fishing and irrigation activities. Although local communities have attempted control measures such as mulching and feeding it to poultry because of its high nutrient availability, these practices have further encouraged its spread into surrounding terrestrial areas. This study was conducted to evaluate the potential of alligator weed as an organic liquid fertilizer and to compare its effectiveness on the growth and yield of the okra crop with that of a conventional organic fertilizer mix and an inorganic fertilizer. Liquid fertilizers were prepared using four concentrations of alligator weed (25%, 50%, 75% and 100%). A traditional organic mixture of Gliricidia and neem leaves, an inorganic fertilizer treatment, and an untreated control were also included. The experiment was arranged in a Completely Randomized Design with four replicates. Fertilizer samples were analyzed for nitrogen, phosphorus, potassium (NPK), pH, and electrical conductivity (EC). Growth and yield performance were evaluated by measuring crop height, stem circumference, total pod number and total pod weight. Despite relatively low NPK concentrations, the 50% alligator weed liquid fertilizer treatment achieved the highest yield performance (1,145.26 g and 64 pods), which was comparable to inorganic fertilizer and superior to both the organic mixture and the control. Utilizing alligator weed not only provides a sustainable alternative to inorganic fertilizers but also offers an eco-friendly strategy for managing a problematic invasive species while recycling nutrients within agricultural areas.