In
a greenhouse experiment we evaluated the application of slurry generated by a
biogas reactor of agroindustrial residues. The objectives of this study were to
determine the response to slurry application on dry matter production and nutrients
absorption of Setaria italica (setaria), and to evaluate the effect of the slurry on soil properties. Two
soils, of different texture, were mixed either with slurry or with diammonium phofsphate (DAP)
at 0, 80, and160 kgN ha-1 equivalent rates. The setaria was harvested 68 days after planting, and
separated into leaves plus stems, ears, and roots. Total biomass and content of
N, P, K, Ca, Mg, Cu, Fe, Mn, and Zn were determined in each fraction. In the
soil we determined pH, electric conductivity (EC), organic C, available P,
mineral N, and exchangeable
cations. Although the biomass produced and the amounts of nutrients absorbed
were different in the two soils, in both of them setaria responded to the
slurry application. The amounts of N absorbed from slurry and DAP were similar,
indicating that the N from the slurry was readily available. The slurry
application also increased the absorption of other macro and micro nutrients
(P, Ca, Mg, and Zn). No significant changes in soil exchangeable cations, pH,
and EC were observed at setaria harvest. In the silty soil the crop almost
depleted the mineral N in all treatments, but in the sandy soil large amounts
were left, especially in the treatments with slurry. This fact highlights the
importance of a careful dosage of this soil amendment, to avoid the excess of
mineral N, which is potential pollutant for the environment. It can be
concluded that the use of slurry from the reactor had a positive effect on the
nutrients availability, without negative effects on soil properties.