Dry Matter Production of Corn in Soils Amended with Gelatin Industry Biological Sludge.

Soils have been used as the final destination for urban, agricultural and industrial wastes. As long as these wastes are within the pollutant limits for heavy metals and quality guidelines for microorganisms they can be used as sources of nutrients to the plants and improving soil chemical, physical and biological properties. The experiment was carried out in a completely randomized factorial scheme with two Ultisols (sandy clay loam and sandy clay), six biological sludge rates (zero; 100; 200; 300; 400 and 500 m³ ha^-1) and three replicates. Soil samples were collected in 0-20, 20-40 and 40-60 cm depth and placed in PVC columns. The gelatin industry biological sludge showed: solids = 1.01%; pH 8.2; EC = 4.32 mS cm^-1; total-N; NH₄⁺-N; NO₃^--N; organic-C; Ca and Na concentration in dry weight, equal to 74.4; 23.6; 0.6; 131.2; 97.9 and 57.3 g kg^-1, respectively, and C/N ratio = 1.8. In each column were maintained four corn plants and 45 days after emergence, shoots were harvested, washed and dried to obtain dry matter. In sandy clay soil the biological sludge increased the dry matter production and the nitrogen amount in corn shoot. The largest biological sludge rate (equivalent to 500 m³ ha^-1) increased by 114% in dry matter production compared to the control, possibly due to the nutrients supply by the biological sludge, particularly nitrogen. Moreover, there was an increase in 75 and 121% of sodium amount in corn shoot, for the sandy clay and sandy clay loam, respectively.