Impact of sewage sludge on growth indices of Sorghum bicolor: an alternative approach to conventional agriculture

Improvisation of agricultural operations aimed at sustenance has been keenly sought. Raising superior cultivar and adopting a “greener” route to soil health are the core concerns. Unprecedented use of chemical fertilizers has raised serious environmental and health concerns. Sustainable options in terms of re-utilisation of sludge as a prospective compost has been a focal theme of recent studies, leveraging into attainment of circular economy. Sorghum bicolor was chosen based on its regional consumption, ease in its availability and cultivation. Upon utilization of sewage sludge and untreated sewage effluent as growth promoters, it exhibited significant growth pattern indicative of resource recovery, mobilisation and utilization. Performance indicators of Sewage Treatment Plant (STP) were found to be in adherence with permissible limits of effluent release. Total Solids (TS) were found to be in a range 102.933 ± 0.23–111.504 ± 0.14 mg/l as compared with 110.808 ± 0.21 mg/l for municipal water. Likewise, observations of Total Dissolved Solids (TDS) were 102.804 ± 0.21- 102.804 ± 0.21 mg/l as contrasted with municipal water (110.649 ± 0.41 mg/l). Total Suspended Solids (TSS) were significantly lower (88.131 ± 0.01–99.28 ± 0.21 mg/l) as compared with 90.146 ± 0.008 mg/l for municipal water. pH was found to be in neutral range, reflecting a sustained end of pipe treatment approach. Growth indicators of Sorghum bicolor (% increase in shoot length (88.58%) and root length (87.09%) reflected a cumulative significant increase when contrasted with control groups. Our findings highlighted an enhanced effect of effluent from aeration tank which exhibited a profound growth, also expressed in terms of Chlorophyll (0.096 ± 0.03–0.134 ± 0.02) (mg/g). These preliminary findings align with utilisation of dried sludge with effluent collected from aeration tank of STP as a prospective hybrid compost model, which may further be explored for other cash crops.