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Vermiliquer (vermicompost leachate) as a complete liquid fertilizer for hydroponically-grown pak choi (Brassica chinensis L.) in the tropics
The processing of organic wastes and composts by worms results in castes and vermiliquer (i.e., vermicompost leachate). Both castes and vermiliquer contain plant available nutrients, the latter better suited to hydroponic operations, but the optimum pH for worm productivity and vermiliquer production makes the latter too alkaline for hydroponics. We show that under optimal hydroponic management practices, the growth and yield of pak choi (Brassica chinensis) based entirely on pH buffered vermiliquer collected after 8–10 weeks of vermicomposting was comparable with those treated with a conventional inorganic hydroponic fertiliser. Nitric acid proved to be a superior pH buffer compared with orthophosphoric acid. The total fresh weight in the nitric acid buffered vermiliquer treatments ranged from 70% to 98% of the total fresh weight of the control. However, the non-buffered hydroponic production of pak choi using off-line (batch) vermiliquer or direct linkage with vermifarms was not successful. There were no statistically significant differences between pak choi yields using vermiliquer from kitchen wastes or composted paunch materials. A 50% dilution of vermiliquer led to yield loss, but less proportionately than the dilution, and the use of pot hydroponics rather than nutrient film technique (NFT) hydroponics led to a better performance of pak choi under less favourable conditions. This is the first report of comparable yields between vermiliquer treatments and an inorganic nutrient source and highlights the feasibility and commercial potential of this hydroponic practice.