Calcium and magnesium on an Oxisol after the application of urban and industrial wastes

Abstract

Urban and industrial wastes applied to crops under no-tillage system (NT) can promote benefits to the physical, chemical and biological attributes of the soil. The reuse of such materials reduces the input of fertilizers, providing greater environmental and economical sustainability. In addition of acting as regulators of soil acidity, some of these residues are excellent sources of plant nutrients, such as calcium (Ca) and magnesium (Mg). In this context, we aimed to analyze the Ca and Mg contents on an Oxisol under NT after surface application of urban and industrial wastes. The experimental design was a randomized block, in a 4x4+1 factorial scheme, with three replications. The treatments consisted of four residues: LC - sewage sludge centrifuged with addition of virgin lime (CaO); LB - sewage sludge from biodigester with addition of polyelectrolytes; E - steel slag; and Lcal - lime mud, applied at doses 0, 2, 4 and 8 Mg ha^-1. In soil samples collected from 0-5, 5-10, 10-20 and 20-40 cm layers, were evaluated the Ca and Mg contents. The E and Lcal residues showed the highest Ca contents in the soil during the two years of cultivation. As for the Mg contents in the soil, the highest values were obtained with the application of LB. Higher Ca and Mg contents were found up to 20 cm deep.