Biosolid effects on soil and native plant production in a degraded semiarid ecosystem in central Spain

Anaerobically digested biosolid was surface-applied at three rates, 40, 80 and 120 Mg ha -1 , to a degraded semiarid ecosystem of the central region of Spain to determine the effects of biosolids on soil chemical properties, total plant cover and total above ground biomass 1 year after its application. Biosolid amendment had little impact on soil chemistry and nutrient levels. However, available P and N-NO 3 increased significantly after application of biosolids. The concentration of total soil heavy metals, Zn, Pb, Cd, Ni, Cr and Cu increased with the application of biosolids as compared against the control plot, but these increases were not statistically significant. The levels of DTPA-extractable soil heavy metals did not change in the treated plots. Total plant cover and total biomass production increased significantly in the biosolid treated plots. The most favourable soil and vegetation results were found in 40 and 80 Mg ha -1 biosolid application rates.