Effect of raw sewage sludge and sewage sludge biochar on soil physicochemical properties and seed germination of Solanum lycopersicum

Abstract

AbstractVarious experts have been concerned about the safety usage of sludge generated during wastewater treatment and its disposal in the environment. Biochar made from sewage sludge was studied for its efficiency in enhancing soil quality, reducing heavy metal uptake, and potential benefits in agriculture areas to enrich the soil. The objectives of the present study were to examine the feasibility of raw sewage sludge (RSS) and sewage sludge biochar (SSB), which were produced at 400 and 500°C, as a soil amendment, and the effect of sewage sludge biochar on seed germination of Solanum lycopersicum. Present study included seven treatments: (i) T0 (Control); (ii) T1 (RSS, 1%); (iii) T2 (RSS, 2.5%); (iv) T3 (SSB400°C, 1%); (v) T4 (SSB400°C, 2.5%); (vi) T5 (SSB500°C, 1%); and (vii) T6 (SSB500°C, 2.5%). The addition of sewage sludge and its biochar enhanced electrical conductivity (EC), total organic carbon (TOC), sodium (Na) and potassium (K), and soil enzymatic activity when compared to control. The pH value of the soil amended with RSS increased by 0.04–0.1 units as compared to control. The treatments with the higher concentration (2.5%) of RSS and SSB significantly increased the concentration of Na whereas, SSB400°C, 2.5% significantly increased the K concentration in soil in comparison to control. The TOC in soil increased in all the RSS and SSB amended treatments and ranged between 1.16 and 1.83 %. Seeds of Solanum lycopersicum treated with SSB at 500°C had shown maximum germination (90%) and germination index (103.01 ± 1.41). The increase in the alkaline phosphatase activity was significant and was maximum 25.2 μg 4‐nitrophenol g−1 soil h−1 for T2 followed by T4 which was 24.9 μg 4‐nitrophenol g−1 soil h−1. The results demonstrate that the RSS and SSB at 2.5% concentration are potential organic amendments to promote the soil nutrients.