the ameliorating effect of poultry manure and its biochar on petroleum-contaminated soil remediation at two times of cultivation

To investigate the effect of total petroleum hydrocarbons (tphs) contamination levels, organic fertilizers (poultry manure (pm) and poultry manure derived biochar (pmb)) and time of cultivation on growth characteristics of oat (avena sativa) and barley (hordeum vulgare) in tphs-contaminated soil, a pot experiment was conducted. the two studied plants had the potential for soil phytoremediation in highly tphs contaminated soil; however, the plant growth decreased significantly with increasing the tphs contamination. a high tphs content had a toxicity effect on plant growth and degradation of tphs. the results showed that the best degradation was achieved in the lowest tphs level for soil cultivated with barley plant and the degradation of tphs increased by adding fertilizer. according to the results in tphs contaminated soil samples, the highest average of relative growth rate (rgr) of roots observed in barley plants as compared to the oat plants. also, at each period of growth, barley plants showed an increased root/shoot ratio in tphs contaminated soil compared to the oat plants (27.6% after 10 weeks and 64.17% after 20 weeks). application of pmb improved mean shoot height, mean root, and shoot weight by about 17.25, 52.7, and 33.88% for oat plants, and 4, 10.23, and 46.28% for barely plants compared to the un-amended treatments, respectively. the most degradation was achieved after 20 weeks for pmb treatment with barley plant at the lowest tphs level (53.41%) in which oat degraded more than 45% of tphs from the soil. generally, the results showed that phytoremediation of tphs can be affected by different factors such as type of plant, type of fertilizer application, and period of remediation.