Effect of a commercial peat moss-shrimp wastes compost on pucinellia growth in red mud

Revegetation of red mud can be difficult without chemical or organic ameliorant for red mud. A greenhouse experiment was conducted to examine the short-term effect of a commercial peat moss-shrimp wastes compost on the growth of pucinellia (Pucinellia distorts L.) in a bauxite residue (red mud) from the Alcan's Vaudreuil alumina refinery at Jonquière (Québec), Canada. Characterization of the red mud revealed that the residue was strongly alkaline (pHse=11.4) and contained soluble salts (ECse=10.3 dS m−1), soluble Na (2743 mg L−1), soluble Al (275 mg L−1) and low levels of plant-available nutrients. Red mud components included approximately 40.4% Fe, 18.3% Al, 13.4Percnt; Si, 7.5% Ti, 6.7% Na and 3.5% Ca expressed in oxide. Hematite (∝Fe2O3) was the main mineral in the red mud. The results of the revegetation study have shown that compost amendment treatments affected pH values, salinity, organic carbon and DTPA-exlractable Al contents compared to the control. The highest rate (45%) of compost reduced the initial pH to about 9.3. The dry weight yield of pucinellia increased as the percentage of compost in the red mud increased. However, survival and plant growth were very poor when the compost was applied at 18 and 23% rates. The critical substrate pH value for pucinellia growth was between 9.5 and 9.7. In general, the leachates from the compost amended red mud are slightly more concentrated with respect to Al, compared with the unamended red mud (control).