Plant and Soil Responses to the Application of Composted MSW in a Degraded, Semiarid Shrubland in Central Spain

Abstract

Composted municipal solid waste (MSW) was assessed as a soil amendment material for restoring the canopy cover of a degraded soil in an area with a Mediterranean climate. Four rates (0, 40, 80 or 120 Mg ha−1) of MSW were surface-applied to a calcareous soil in central Spain and the effects on soil properties and the native plant community recorded over the next five years. Soil N, P and K levels increased significantly after application. Soil organic carbon (OC) increased with the amount of MSW applied, but the differences were small and inconsistent. Soil total Zn, Pb, Ni and Cu increased in the MSW-treated soils compared to the controls, but levels were still below the maximum allowed by Spanish legislation. DTPA-extractable soil Zn and Cu were the only heavy metals studied that increased with MSW application, but their concentrations were still adequate for plant growth. Total aerial plant biomass yields and canopy cover increased with MSW amendment compared to the control treatment. Plant production increased three fold in the amended plots in the first years and than declined with time, although no consistent trends were observed. The percentage canopy cover ranged from approximately 82 to 100 % in the MSW treatments and from 43 to 49% in the control throughout the study period. Native plant species richness decreased slightly with increasing MSW rates. Differences in the plant communities developing on the control and MSW-treated plots were observed, with a reduction in perennial species and an increase in annual species after five years. Plant tissue N, P, K, Zn and Cu levels generally increased with the MSW rate. Thus, MSW application have a positive effect on the soil chemical characteristics and on the native vegetation without causing environmental damage. MSW may therefore be of use in the rehabilitation of ecosystems similar to that studied.