The effect of vermicompost obtained from pomace on the growth of lettuce and plant nutrient uptake

The byproduct of the manufacture of olive oil, called pomace, may harm the environment because of the phenolic chemicals it contains and the significant increase in chemical oxygen demand it causes in the receiving environment. A pot experiment was carried out to evaluate pomace use possibilities for agricultural purposes. For this purpose, 50% pomace, 45% animal manure and 5% dolomite were mixed, the mixture were weighed one kg each, one was inoculated with 150 Eisenia fetida (vermicompost), the other was left as it was (compost) and both were incubated under laboratory conditions for 69 days. The vermicompost and compost obtained at the end of the period were incorporated to the soil at doses of 0, 10, 20 and 30 t ha-1 and lettuce plants were grown on the soils placed in pots. Although the results of the experiment showed that the earthworms were more effective in reducing the phenolic matter content of the initial mixture, this effect was not statistically significant. However, the acquisition of phenolic compounds from substrates to lettuce plants was 45% higher in compost application which indicates vermicompost reduced the transition of phenolic compounds to the plant. There was no difference between vermicompost and compost in lettuce yield (p<0.05). Phosphorus concentration in the plant was higher in the compost treatment, while Zn and Mn concentrations were higher in the vermicompost. When the nutrients remaining in the soil after harvesting were evaluated, it was determined that nutrient levels were considerably higher than the control, especially at 40 t ha-1 dose. Based on the overall results it was concluded that the 10 and 20 t ha-1 doses of vermicompost may be used on lettuce cultivation.