Risk of municipal solid waste compost and sewage sludge use on photosynthetic performance in common crop (Triticum durum)

The effect of composted municipal solid waste (MSW) and sewage sludge (SS) on photosynthetic activity of wheat (Triticum durum L.) was investigated. Chlorophyll fluorescence and gas exchange parameters were assessed following application of up to 300 t ha(-1) of MSW compost or SS. 100 t ha(-1) MSW compost was optimal for the plant growth, which showed 78% stimulation as compared to the control. This was associated with higher maximum quantum efficiency (F (v) /F (m)) of photosystem II (PSII) and the actual quantum efficiency of PSII open centers at light adapted state (Delta F/F'(m)). Maximal values of net photosynthetic rate and stomatal conductance were recorded at 100 t ha(-1) MSW compost (+40 and +116%, respectively). Ribulose bisphosphate carboxylase/oxygenase (RubisCO) activity was also significantly stimulated at 100 t ha(-1), while less significant impact was found in SS treatment. A marked accumulation of Ni, Pb, Cu, and Zn in concomitance with membrane lipid peroxidation were observed at 200-300 t ha(-1) MSW compost and SS, resulting in lower photosynthetic activity and altered PSII functional integrity. Altogether, these results suggest that the MSW compost at 100 t ha(-1) would be suitable for wheat cultivation, within the critical limits of heavy metal accumulation. However, long-term field experiments seem necessary to more accurately evaluate the safety of MSW application.