Abstract

The application of biosolids on agricultural soils is a procedure used by municipalities and private companies to dispose, purposefully or inadvertently, of residue. This study evaluated the effects of limed sewage sludge and inorganic or organomineral fertilizers on the chemical properties of red latosol and the contents of chlorophyll A and B in the fresh and dry matter of Urochloa brizantha cv Marandu. The experimental design was composed of randomized blocks due to a lighting gradient in the greenhouse, with 10 treatments and four replications. Treatments included: mineral fertilizer 3-30-10 (120 kg ha^-1 P₂O₅); limed sludge (60 kg ha^-1 N); limed sludge (48 kg ha^-1 N) + mineral fertilizer 3-30-10 (120 kg ha^-1 P₂O₅); limed sludge (60 kg ha^-1 N) + agricultural gypsum (40 kg ha^-1 S); limed sludge (60 kg ha^-1 N) + magnesite (30 kg ha^-1 Mg); limed sludge (60 kg ha^-1 N) + single superphosphate (120 kg ha^-1 P₂O₅); limed sludge (60 kg ha^-1 N) + verdete (60 kg ha^-1 K₂O); limed sludge (60 kg ha^-1 N) + agricultural gypsum (40 kg ha^-1 S) + magnesite (30 kg ha^-1 Mg) + single superphosphate (120 kg ha^-1 P₂O₅) + verdete (60 kg ha^-1 K₂O); organomineral fertilizer 05-24-08 (120 kg ha^-1 P₂O₅) and control with no addition of nutrient sources. Soil properties, pH, V (base saturation), m (aluminum saturation), OM (Organic Matter), P (Phosphorus), K (Potassium), S (Sulfur), Ca (Calcium), Mg (Magnesium), B (Boron), Cu (Copper), Fe (Iron), Mn (Manganese) and Zn (Zinc), as well as the chlorophyll A and B of fresh and dry matter of U. brizantha cv. Marandu were evaluated 30 days after germination. Limed sludge combined, or not, with mineral fertilizers, behaved as a soil corrective, increased the Ca and Mg content of the soil and reduced the Fe and Mn content. The fertilizer sources evaluated did not affect the contents of OM, organic carbon, Cu or B. Single superphosphate mixed with limed sludge and the mixture of gypsum, magnesite, single superphosphate or verdete with limed sludge resulted in greater P and S. content in the soil. Verdete mixed with limed sludge did not increase soil K or chlorophyll B contents. However, Zn contents were increased with the Verdete mixture. The highest level of fresh matter production was obtained with mineral fertilizer, organomineral fertilizer and sludge plus mineral fertilizer. Dry matter production, on the other hand, was increased only by the application of mineral fertilizer.

Key words:  Biosolid, forage, mineral nutrition, organic fertilizers.