Investigating the Effects of Organic Liquid Fertilizer Derived from Vegetable Waste on Moisture Retention, Soil Physical Properties and Yield of Lettuce (Lactuca sativa L.) Grown in the Malkerns Area, the Kingdom of Eswatini

Modern agriculture is experiencing the adverse effects of synthetic fertilizers, as their long-term use has raised significant environmental concerns. These fertilizers can degrade soil quality, disrupt ecosystems, and harm plants, animals, and the environment, particularly when misapplied or used in excessive quantities. Organic fertilizers can serve as an alternative to synthetic fertilizers, as they play a crucial role in promoting the growth of beneficial microorganisms in the soil. The main aim of this study was to investigate the effect of organic food waste on the condition of soil and the yield of vegetables. The experiment was a randomized block design with N:P:K at a ratio of 2:3:2(37) inorganic fertilizer, organic fertilizer (vegetable food waste), and no fertilizer as the three treatments using no fertilizer as a control. There were three replications per treatment. The vegetable food waste was processed in a closed container along with the addition of stillage and sugar in anaerobic conditions for 3 weeks. Parameters measured included the soil moisture content at 4 weeks and 6 weeks after planting, the soil porosity, the lettuce's fresh and oven-dry mass, and the changes in soil nutrient content before and after the application of the treatments. The vegetable food waste liquid fertilizer was analysed and the NPK values were found to be 0.83 %, 16.5 mg/kg, and 20.62 cmol/kg, respectively. After the application of treatments in the soil, the results of the study showed that vegetable waste had the highest yield per head (355.5 g) followed by synthetic fertilizer and no fertilizer treatment (control) with 283.2 g, and 253.1 g, respectively. Similarly, vegetable food waste had a higher moisture holding capacity of 0.237 cm3/cm3 while synthetic fertilizer and the control both were 0.139 cm3/cm3. The results obtained from the study showed that liquid vegetable food waste fertilizer can be used as an alternative to synthetic fertilizer to increase crop yield and improve soil physical properties while reducing the negative impact of synthetic fertilizers on the environment as well as the environmental effect of disposing of vegetable food waste in landfills. In this study, the nutrient value of ordinary vegetable food waste is converted into a highly useful product as liquid fertilizer. This technique can empower and is expected to reduce the burden on the farmers, economically wise.