Abstract

"The potential toxicity of urban sewage and farmed salmon sludge, as well as their fertilizer potential, was evaluated by a battery of tests carried out with lettuce (Lactuca sativa L.) and annual ryegrass (Lolium multiflorum Lam.) cv. Winter Star. Wastes were evaluated in a Patagonian soil (Andic cryofluvent) and a granitic soil (Ultic Palexeralf). The treatments were municipal sewage sludge (MSS), salmon ground-farming waste (PSW) and salmon lake-farming waste (LSW) at different rates: 25, 50, 75, 100 and 150 t ha-1. Bioassays in lettuce were conducted for germination index (GI), radicle and hypocotyl structure length. Test in ryegrass were conducted for aboveground biomass yield. The phytotoxicological results from Patagonian soil showed significant differences (P ≤ 0.05) among sludge, where the highest values for GI, radicle and hypocotyl length were for LSW, followed by PSW. Results from granitic soil showed no significant differences among sludge added. In both soils, MSS treatment at application rate of 150 t ha-1 presented the smallest radicle length, not showing development of the hypocotyl structure. Biomass data indicated that MSS, PSW and LSW sludge can be applied at 25 to 150 t ha-1 on Patagonian soil and only LSW sludge on granitic soil. However, its addition should be complemented with N and K inorganic fertilizer to increase pasture yield. MSS and PSW sludge applied at 150 t ha-1 was clearly detrimental for crop yield, especially when applied to granitic soil."