Sustainable weed management and soil enrichment with water hyacinth composting and mineral fertilizer integration

Composting water hyacinth (Eichhornia crassipes) presents a promising approach for managing the weed and the aquatic environment while increasing agricultural production and soil fertility. However, limited research reported on the impact of water hyacinth compost on soil properties and crop production under field conditions. This study aimed to evaluate impact of water hyacinth compost and its combined application with mineral fertilizer on soil properties and crop production. Before field experiments, the compost's phytotoxicity was assessed through bioassays, confirming it was safe for agricultural use with a seed germination index exceeding 80 %. Field trials were conducted using a factorial design with four application rates of water hyacinth compost (0, 8, 16, and 24 t ha^-1) and three rates of the recommended mineral fertilizer for teff production (0/0, 40/23, and 80/46 kg N/P₂O₅ ha^-1). The results indicated that compared to the control group, applying water hyacinth compost increased soil pH by up to 0.69 units and reduced bulk density by 10.3 %. Soil organic carbon, total nitrogen, available phosphorus, cation exchange capacity, and exchangeable potassium increased by 24.3 %, 28.6 %, 80.2 %, 26.2 %, and 112.7 %, respectively. Furthermore, exchangeable acidity and aluminum were reduced by 72.5 % and 78.6 %, respectively. The maximum grain yield (1826 kg ha^-1) and total biomass (8020 kg ha^-1) of teff were achieved by applying 24 t ha^-1 of water hyacinth compost coupled with the full rate of mineral fertilizer. However, compared to adding only full fertilizer, the grain yield that resulted from applying water hyacinth compost at 16 and 24 t ha^-1 along with half of the suggested mineral fertilizer was superior. This implies that water hyacinth compost could substitute 50 % of the mineral fertilizer required. In conclusion, composting water hyacinth offers a dual benefit of weed management and soil enrichment. This could be a sustainable strategy to mitigate weed proliferation while improving soil quality and crop production.