The practice of correcting soil acidity by surface application of pH-correcting materials on crop residues in the no-till system is restricted to limestone. No further studies are available on the use of steel slag, lime mud, and centrifuged sewage sludge. The objective of this study was to evaluate soil acidity and yield of soybean as a function of surface application of centrifuged sewage sludge, lime mud, steel slag, and dolomitic limestone. The study was conducted on a dystrophic Clayey Rhodic Hapludox soil, during the 2002_2005 cropping seasons, under notill system. Treatments consisted on surface application of slag _ E, lime mud _ Lcal, centrifuged sewage sludge _ LC, dolomitic limestone, and zero application of correcting materials, conducted in a random block design with four replicates. Surface application of steel slag, lime mud, and centrifuged sewage sludge allowed soil acidity correction, Ca2+ displacement, increased base saturation, and Al3+ reduction down to 40cm depth, whereas for limestone those effects occurred down to 20 cm. The interaction among those factors promoted a soybean yield increase for the LC, E, Lcal, and limestone treatments in the 2003/04 and 2004/05 seasons, as well as for the LC and E treatments in the 2002/03 season, under the no-till system.
Sewage sludge; steel slag; lime mud; limestone
