Effects of Soil Fertilization Using Compost of Solid Household Waste on the Heavy Metals Content of the Productions

This study was conducted to evaluate the chemical quality and fertilizing value of naturally occurring compost in the City of Daloa landfills. The treatments consist of i) lettuce culture on unfertilized soil or control, ii) lettuce culture on soil supplied with 250 kg/ha of NPK mineral fertilizer of formula 12-22-22 and iii) lettuce culture on soil amended with 40 t/ha of compost, laid out in a Randomized Complete Block Design (RCBD) with three replicates. Results indicate that the compost used contained significant amounts of N (0.88±0.09 g/kg), P2O5 (0.173±0.021 g/kg) and K2O (0.278±0.016 g/kg). This compost also contains, but in small amounts, toxic heavy metals such as copper (233.183±3.21 mg/kg), lead (113.775±2.55 mg/kg) and zinc (141.783±3.03 mg/kg). Regarding the crops, the analyzes revealed that lettuce grown in the presence of NPK and compost absorbed more heavy metals than those grown on the control soil. With NPK, heavy metal concentrations increased steadily in crops during all the crop cycles when, with compost, these concentrations remained almost stable between the first and second crop cycles before growing during the third cycle. It was concluded that fertilization, whether mineral or organic, can promote heavy metal accumulation in crops. Thus, the fertilization of agricultural soils should be conducted with great care.