Availability of soil nutrients, quality of grains and yield of soybean in soil treated with sewage sludge

Abstract

The objective of this work was to evaluate the direct and residual effects of sewage sludge soil application, as a source of phosphorus, on soybean yield, on grain quality for human consumption, and the potential of NO3- leaching. The experiment was carried out in the field, and the following treatments were compared: absence of chemical fertilization and sewage sludge; complete chemical fertilization; inoculated soybean plus dose 0 of sludge; inoculated soybean plus 1.5 t ha-1 of sewage sludge; inoculated soybean plus 3 t ha-1 of sewage sludge; inoculated soybean plus 6 t ha-1 of sewage sludge; and inoculated soybean plus chemical fertilization, except nitrogen. The highest sewage sludge doses resulted in highest soybean yield, in the first and second year. Contents of several elements in soybean grains, under sewage sludge treatments, were not significantly different from those obtained in the control and chemical fertilization treatments. Losses of NO3- to the environment may occur, mainly in the beginning of crop growth cycle.