Effects of Tabriz petrochemical sewage sludge on the soilcharacteristics and tomato growth

For purpose of biological sludge effects study on the biochemical properties of Ahar regionHaplocambid soil, the experiments accomplished on pots containing ۵ kg soil, ۷ levels ofbiological sludge and four replications. The results indicated that with increase of sludgeapplication, number of microorganisms, respiration rate, electrical conductivity, organicmatter percent and the percentage of total nitrogen have increased significantly. Theapplication of sludge on amount of soil carbonates and C/N ratio doesn't have significanteffects; on the other hand the effect of sludge application on soil pH alterations has shown thedecrease of pH in high levels applications in comparison to ۲۰ ton/ha is been significant at۰.۰۵ probability level. As well as to study the effects of sewage sludge on tomato seedlinggrowth, one series of pot experiments; each pot containing ۱۷ kg soil, were conducted in arandomized complete design with eight replications. The used treatments were; five levels ofsewage sludge (۵, ۱۰, ۲۰, ۳۰, and ۴۰ tons/ha) and two control treatments (T۱, without sewagesludge, and T۲, only complete fertilizers). Analysis of variance for weights of fresh and dryover-ground parts showed that they were significantly higher than T۲ (sludge + completefertilizer) with a one percent level of probability in comparison to five and ten tons perhectare of sewage sludge treatments. In treatments with usage of more than ۱۰ tons perhectare weight of fresh and dry over-ground parts due to toxic effects decreased drastically.For example, applying ۳۰ tons of sewage sludge decreased dry weight by ۲۰ percent andfresh weight by ۴۴ percent in comparison to T۲ treatment. Mean comparisons revealed thatthe water content of tomato plants did not differ significantly in comparison to T۲ when ۱۰-۲۰ tons of sewage were applied, but its difference was significant with a five percent level ofprobability when ۳۰, and ۴۰ tons of sewage sludge were applied. Analysis of variance fordry, fresh, and water content of fruits also showed that their differences with T۲ were nonsignificantwhen ۵ and ۱۰ tons/ha sewage sludge were applied to the pots. However, applyingsewage sludge beyond ۱۰ tons per hectare reduced all these three attributes significantly.Applying ۲۰, ۳۰ and ۴۰ tons/ha of sewage sludge delayed growth and development andcaused apparent necrosis in the leaf margins of young and mature plants within the firstmonth, while the toxic effects of sludge on necrosis decreased during later growth stages.Higher availability of iron (Fe) at higher sludge application rates along with soluble cationand anion concentrations in soil solution, especially chlorine, and probably other side effectswere caused by sludge application and consider the factors that may have toxic effects onplants.

کلیدواژه ها:

Sewage sludge ، Tomato