Effects of Gamma Irradiated and Non-Irradiated Sewage Sludge on Growth Characteristics, Leaf Chlorophyll Index, and Macronutrients Concentrations in Basil

Irradiation of sewage sludge (SS) with gamma-ray is regarded as a promising alternative and rapid method for risk mitigation of this waste in ecosystems. The effects of 13 treatments (15, 30, and 60 g kg(-1) of non-irradiated SS and irradiated with doses of 5, 10, and 20 kGy gamma-ray and soil without SS and irradiation as the control treatment) was investigated on the growth, herbage yield, leaf chlorophyll index, and concentrations of macronutrients in basil (Ocimum basilicum L.) root and shoot in a completely randomized design with three replications under greenhouse conditions. The results showed that application of gamma-irradiated and non-irradiated SS positively affected the concentrations of nitrogen, phosphorus, potassium, sodium, calcium, and magnesium in basil shoot and root. The highest and lowest dry weights of root and shoot, plant height, leaf area, and leaf chlorophyll index were observed in 30 g kg(-1) SS irradiated with 20 kGy absorbed dose and 60 g kg(-1) non-irradiated SS, respectively. In <= 30 g kg(-1) SS, the gamma irradiation absorbed dose did not significantly change the growth parameters, thus the use of <= 5 kGy absorbed dose may be suggested to stimulate positive effects on basil growth. Also, in 60 g kg(-1) SS, the restrictive effects were mitigated by increasing the absorbed dose, but the use of >= 5 kGy absorbed dose may not cost-effective. Therefore, in order to improve nutrition and growth of basil plant, application of <= 30 g sewage sludge irradiated with 5 kGy absorbed dose of gammaray per kilogram soil can be suggested under similar conditions.