The search for alternative plant fertilizer materials is crucial because of continuously increasing food demand and the growing human population. This experiment hypothesized that the measured parameters of maize (Zea mays L. cv. Armagnac) linearly change with increasing concentrations of sewage sludge and compost (0% as control, 25%, 50%, and 75% as m/m%) treatments at the three-leaf stage. In addition, the goal of this study was to compare the effects of sewage sludge and compost on maize’s characteristics in a greenhouse pot experiment.

The results showed that all three of the applied compost concentrations had positive effects on the initial growth of the plants, while sewage sludge increased the plant height at 25% and 50% treatments compared to the control. All the applied treatments increased chlorophyll-a, chlorophyll-b, and carotenoid contents related to the control. The proline content indicates that all treatments stressed the plants, though the nature and extent of the stress are not clear yet. In addition, the amount of malondialdehyde (MDA) and the activity of superoxide dismutase (SOD) did not change significantly compared to the control. This indicates that there is no correlation among MDA, proline content, and SOD activity in this experiment. Chlorophyll-b content was 2.8, 2.5, and 3.2 times higher at 25%, 50%, and 75% sewage sludge treatment relative to compost treatment. Concerning carotenoids, these values were also 33%, 25%, and 41% higher when plants were grown on sewage sludge. The concentration of proline and MDA content were not significantly different between the 25% sewage sludge and compost treatments. At 50% and 75% treatments, the MDA content was 25% and 33% higher while the proline concentration was 37% and 53% higher in the sewage-sludge-treated plants, respectively. The activity of SOD was significantly higher at 25% and 75% sewage sludge concentrations relative to the compost treatments.