Saturday, 15 July 2006

Plant and Soil Responses to Biowaste Application in a Degraded Semi-Arid Ecosystem.

Ingrid Walter1, Fernando Martinez2, and Gabriela Cuevas1. (1) INIA, Dept of the Environment, Carretera de La Coruņa Km 7.2, 28040 Madrid, 28080, Spain, (2) INIA, Dept of the Environmental, Carretera de La Coruņa Km 7.2, 28040 Madrid, Spain

Reestablish the plant canopy cover is the key to control soil erosion in degraded semi-arid ecosystems, improving soil quality and increasing SOC contents. The addition of biosolids is potentially a convenient means of enhance soil fertility, since their high nutrient and organic matter content exercise a positive effect on several soil properties, and consequently speed plant establishment. Biosolid was surface-applied once at rates of 0, 20, 40, 40, and 120 Mg ha-1 to a degraded grassland sited in southeast of Madrid, Spain. The climate of the study area is Mediterranean, belonging to semiarid type. The soil is described as Lithic Xerorthents. The plant canopy cover was scarce (< 50 %) and mainly composed of and herbaceous mixture and slowly growing low shrubs. Natural vegetation and soils data were collected for five years following treatment (1997). The surface soil layer (0-15 cm) showed a initially increased in soil N, P and K with increasing biosolids rates, but then decreased over time. Total SOC levels also showed a increased but this effect did not show consistent trends. During the five years following treatment (1998-2002), total plant biomass and total plant canopy cover increased significantly by the biosolids addition and remained higher than in the control. The species richness of native plant decreased with increasing biosolids rates. Higher rates of biosolids application were associated with increased concentration of N, P , Zn, and Cu in plant tissue relative to the unamended plot. Tissue Pb, Cd, Ni, and Cr concentration did not increased significantly in the study period. Biosolids applied at the rate of 80 Mg ha-1 gave rise to the most favorable soil and vegetation results. The results confirm the usefulness of biosolids as an organic amendment for restoring degraded sites and could contribute to reduce soil erosion in semiarid Mediterranean ecosystems.

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