Saturday, 15 July 2006
170-9

Evaluation of Waste from a Brazilian Siderurgy Industry as Alternative for Soil Acidity Correction.

Renildes Fontes, Univ Federal de Viçosa, Av. P.H. Rolfs S/n, Vicosa, 36571-000, Brazil

Industrial wastes or residues added to the environment may cause problems if disposed into natural systems without well defined criteria. Soil, water, plants and the whole environment may be affected. Siderurgy and metallurgy wastes, generally produced in huge amounts, need to be disposed appropriatelly in order to avoid environmental problems. Some industrial wastes have been added to agricultural areas aiming to combine an environmentally apropriated way for waste disposal with a possible action for improvement of soil conditions for agricultural exploration. Many industrial residues have porperties that qualify them for soil acidity correction and contain some essential nutrients which could be available for plant uptake after the equilibrium in the residue-soil mixture. In Brazilian agriculture, soil acidity correction is mandatory for the majority of the soils. Furthermore, most Brazilian soils have low natural fertility, needing nutrient inputs for crop production. Some siderurgy and metallurgy industry wastes in Brazil have been tested for soil pH correction and as source of nutrients for plant growth. This work evaluated the viability of using a waste from a Brazilian siderurgy industry as alternative to correct the soil acidity. It was tested a industrial waste mixture composed by the combination of three industrial residues: a desulfuration powder, a rotation oven mud and a calcinated dolomite. The Total Neutralization Power (TNP) of the material is 80 % and the concentrations of CaO and MgO equal to 34 dag/kg and 16 dag/kg, respectively. A comercial lime (TNP = 80 %; CaO = 30 %; MgO = 12,1 %) and a mixture of gypsum plus CaCO3 (TNP = 100 %; CaO = 56 %) were used for comparison. Lettuce was grown in a clayey distrofic Yellow-Red Latosol (Oxisol) collected at 0-20, 20-40 and 40-60 cm depth. The treatments were set with 4 doses of each material used as corrective for soil pH. The doses were calculated based on the soil characteristics and defined as: dose 1 = no corrective material addition; dose 2 = ½ of the recommeded corrective, based on the soil analysis ; dose 3 = the recommended dose of corrective, based on the soil analysis; dose 4 = 3 times the recommended dose of corrective, based on the soil analysis. The doses in t/ha were: 0.0, 4.2, 8.4, and 12.6 for the waste mixture and for the comercial lime, and (0.0 + 0.0), (1.7 + 3.4), (3.4 + 6.0), and (4.1 + 10.2) t/ha for the gypsum mixture (gypsum + CaCO3). The plants were grown in PVC recipients (15 cm diameter, 60 cm height, 10.8 dm3 soil) with the treatments applied only in the 20 cm surface layer. Dry matter (DM) yield increased as the corrective doses increased (Table 1), the regression analysis showed a quadractic response to the treatments. The contrasts showed no diference between the DM production among the treatments indicating that the waste, the comercial lime and the mixture had the same efficiency for soil acidity correction. The regression analysis showed 10.6 t/ha waste and 2.36 t/ha comercial lime as the doses to obtain maximum physical production (23.85 g and 23.32 g, respectively). For the gypsum + CaCO3 mixture the doses to get the maximum physical production were 4.30 t/ha and 8.76 t/ha, respectively, to produce 23.38 g DM. The dry matter yield of lettuce (mean of three replications), after 60 days of growth in soil treated with a Industrial Waste (W), a commercial lime (L), and a (gypum+CaCO3) mixture (G), were (in grams): 14.86, 20.65, 23.69, 22.81 for doses W1, W2, W3, W4, respectively; 14.07, 19.86, 21.97, 23.22 for doses L1, L2, L3, L4, respectively; and 14.59, 20.67, 22.44, 23.33 for doses G1, G2, G3, G4, respectively.

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