Utilizing sludge from catfish farming to produce vermicompost for improving soil quality

Abstract

Abstract Earthworm organic waste is processed into vermicompost, which is of varying quality depending on the substrate. In vermicomposting, earthworms can promote nitrogen mineralization and effect nitrification. A challenging-to-absorb nutrient will be converted into a nutrient that plants can easily absorb to improve nutrients in soil and increase crop production. In this study, an experimental model of organic fertilizer production from catfish pond bottom sludge was implemented. Sludge from the bottom of catfish ponds is composted with water hyacinth in aquatic ponds to produce organic fertilizer, mature fertilizer is used as a substrate for vermicomposting. The impact of vermicompost on plant growth parameters was evaluated through its use to improve nutrients in soil. Sludge, compost, vermicompost, and soil quality were also evaluated for their physical and chemical properties. Results show that the growth coefficient of earthworms is 129.3±1.15% per 30 days, and the average amount of organic fertilizer created is 126±3.51 kg per 30 days. The quality parameters of vermicompost all meet national standards for organic fertilizer quality. The moisture and total organic matter content in mature fertilizer are 31% and 21.9%, respectively. The content of nutrients N and P increased compared to input materials, the corresponding values reached 2.84% and 0.96%. The C/N ratio is 7.7, microbiological and heavy metal indicators are within the accepted limits. In the experiment using vermicompost to cultivate Brassica rapa chinensis, the yield growth rate was the highest. After 21 days of planting, the growth rate is fast and the height reaches 25.0±0.38 cm. The biochemical composition ensures safety according to food regulations for leafy vegetables. Vermicomposting is recommended as a sustainable and suitable technique for catfish pond sludge utilizing.