Liquid organic fertilizer production for growing vegetables under hydroponic condition

Purpose Liquid organic fertilizers produced from agricultural residues and industrial wastes are becoming increasinglypopular. This study aimed to examine the effect of liquid organic fertilizers produced from waste molasses, distillery slopand sugarcane leaves on the growth of Green Cos Lettuce (Lactuca sativa var. longifolia).Methods Six formulas of liquid organic fertilizers were produced with different ratios of substrates (molasses, distillery slopand sugarcane leaves). The measurements of chemical, microbiological and germination index of fertilizers were studied.Hydroponic using nutrient film technique system was used to grow vegetables with fertilizers.Results Fertilizers showed the ranges of chemical parameters as follows: pH 4.5–7.8, EC 25–33 dS/m, total N 0.14–0.33%,total P2O50.002–0.017%, total K2O0.81–11.8%, OM 0.26–3.25%, OC 0.26–3.20% and C:N ratio 6.14–17.92. Microbiologicalanalysis indicated total microorganism of 9.99–9.05 logCFU/ml. Nitrogen fixers, phosphate and potassium solubilizingagents were found in all formulas. IAA concentration was 1.13–59.53 mg/l. The fertilizers produced after 30 days of fermentationand used at a dilution of 1:100 gave more than 100% germination index showing non-phytotoxicity characteristics.The results for the hydroponic system showed that liquid fertilizer formula 3 (distillery slop: sugarcane leaves: filtrate water1:0.1:0.25 v:w:v) and formula 5 (distillery slop: sugarcane leaves 1:0.25:0.25 v:w:v) demonstrated the best growth performance,which was similar to plants treated with liquid chemical fertilizer.Conclusion This study showed that organic liquid fertilizers formulas 3 and 5 had similar growth promotion properties aschemical fertilizers with Green Cos Lettuce. Moreover, our products are organic and serve as a rich nutrient source for theplant.