Effect of Immature Compost on Available Nutrient Capability and Heavy Metal Accumulation in Soil for Lettuce (Lactuca sativa L.) Cultivation

The aim of this study was to evaluate effects of immature compost on the amount of nutrient content, heavy metal concentration, and application rate that were used for lettuce cultivation. The characteristics of the two composts (Compost A (CA) was immature compost and Compost B (CB) was mature compost) were evaluated upon mixing with commercial soil at 0%, 25%, 50%, and 75% (w/w). The poor chemical characteristics were appeared by use of immature compost as soil amendment; the 50% and 75% rates were weakly acidic at pH 5.39 and 5.50, respectively. The total carbon content at using of 75% of the immature compost and mature compost increased the most to 14.5 and 6.5% and it significantly increased concentrations of the total nitrogen and phosphorus compared to control. As for 75% mature compost rate increased significantly the concentrations of Cu (128 ㎎ ㎏ -1 ), Zn (260 ㎎ ㎏ -1 ), Pb (0.32 ㎎ ㎏ -1 ) and, Cd (0.48 ㎎ ㎏ -1 ) compared to control, and the highest As concentration increased significantly at 75% and 50% (6.69 and 6.28 ㎎ ㎏ -1 ) including in 25% immature compost as 6.48 ㎎ ㎏ -1 . However, all of the high compost rates significantly decreased the shoot biomass of lettuce. The immature compost was potentially amended at an application rate of 25% due to a slight salinity and low risk to heavy metal uptake on lettuce growth. This use may be available if the rate is lower than that used in this trial.