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 o f Spain to determine the effects of biosolids on soil chemical properties, total plant cover and total above ground biomass 1 year after its applicati on. Biosolid amendment had little impact on soil chemistry and nutrient lev els. However, available P and N-NO3 increased significantly after applicati on of biosolids, The concentration of total soil heavy metals, Zn, Ph, Cd, Ni, Cr and Cu increased with the application of biosolids as compared again st the control plot, but these increases were not statistically significant . The levels of DTPA-extractable soil heavy metals did not change in the tr eated plots. Total plant cover and total biomass production increased signi ficantly in the biosolid treated plots. The most favourable soil and vegeta tion results were found in 40 and 80 Mg ha(-1) biosolid application rates.