ment 378 (2007) 81–83www.elsevier.com/locate/scitotenv

Science of the Total Environ

Revegetation of abandoned agricultural land amended with biosolids

Francisco de Andrés, Ingrid Walter ⁎, José Luis Tenorio

Dpto. de Medio Ambiente, INIA, Apdo. de Correos 8111, 28080 Madrid, Spain

Available online 15 February 2007

Abstract

This paper reports the effects of applying 0 and 40 Mg ha−1 of biosolids (composted sewage sludge) on the revegetation ofabandoned cropland in central Spain. The experimental vegetation consisted of four wild leguminous species: Coluteaarborescens, Dorycnium pentaphyllum, Medicago strasseri and Retama sphaerocarpa. The survival and growth of these shrubswere evaluated over 24 months after planting, as was the production of biomass by the spontaneous herbaceous vegetation.Application of the biosolids increased shrub growth, although it was also associated with a slight reduction in shrub survival. Thespontaneous vegetation became quickly established in the amended plots; its biomass production was significantly greater than inthe control plots.© 2007 Elsevier B.V. All rights reserved.

Keywords: Revegetation; Biosolids; Wild leguminous shrubs; Spontaneous herbaceous vegetation

1. Introduction

The climate of the Mediterranean area renders it oneof the most affected regions due to erosion. In manyplaces, the abandonment of cultivated fields is resultingin rapid water erosion, the elimination of fertile soillayers leading to severe degradation of the environment(Holz et al., 2000). Successful revegetation can beachieved, however, by the implementation of practicesthat improve soil fertility and/or by planting species thattolerate the stressful conditions encountered in suchsoils. A single application of biosolids (the compostedby-product of domestic wastewater treatment plant) andthe subsequent planting of wild leguminous shrubs hasbeen proposed for rehabilitating erosion-affected soils incentral Spain (Gil et al., 2001; de Andrés et al., 2003).Biosolids are a valuable source of organic matter and

⁎ Corresponding author. Tel.: +34 91 347 67 38; fax: +34 913 57 22 94.E-mail address: walter@inia.es (I. Walter).

0048-9697/$ - see front matter © 2007 Elsevier B.V. All rights reserved.doi:10.1016/j.scitotenv.2007.01.017

nutrients and can have positive effects on soil physical,chemical and biological properties.

The aim of this study was to determine the effects of aone-time application of biosolids to a degraded soil onthe survival and growth of four wild leguminous shrubspecies, and to determine the effects on biomass pro-duction by spontaneous herbaceous vegetation.

2. Materials and methods

The study was performed in 2001 on an abandonedsoil at the INIA's “La Canaleja” experimental estate(35 km east of the city of Madrid). This soil was verylow in organic matter content, had a high pH, wasmoderately rich in carbonates, and was classified as aTypic Haploxeralf Calciorthid according to Soil Taxon-omy criteria. The climate of the area is Mediterraneancontinental; the zone is classified as semi-arid. Thebiosolids (composted, anaerobically-digested sewagesludge) applied to this soil were the product of a mixtureof the wastewater treatment plants of Madrid. The heavy

Fig. 1. Percentage survival (1.a) and height (1.b) of the wild shrubs inthe biosolid-amended (B) and control soils (C) at 12 and 24 months aftertheir establishment. Different letters above the bars indicate significantdifferences between treatment within a species and sampling time at the0.05 probability level (determined by Duncan's test). Ca: Colutea arbo-rescens; Dp, Dorycnium pentaphyllum; Ms: Medicago strasseri; Rs: Re-tama sphaerocarpa.

Table 1Main physical–chemical soil characteristics for the treatments appliedat 12 and 24 months after planting (soil surface, 0–30 cm)

Social physical–chemical C B

Months

12 24

pH (1:2.5 H2O) 8.5a 8.0b 8.2abEC (dS m−1) 25 °C 0.14b 0.20a 0.18abCaCO3 (g kg−1) 132 130 132Oxidable OM (g kg−1) 9.62 10.4 9.32N (g kg−1) 0.33b 0.43a 0.48aN–NO3 (mg kg−1) 2.69b 4.41a 4.75aN–NH4 (mg kg−1) 10.4 9.33 7.90Extractable P (mg kg−1) 13.8b 33.7a 24.9aExtractable K (mg kg−1) 290b 310a 270b1Total Zn (mg kg−1) 25.1b 62.9a 58.9a1Total Cu (mg kg−1) 8.76b 14.4a 13.8Texture Clay loam

Mean values followed by different letters within the same line aresignificantly different (P≤0.05).C: control soil; B: biosolid-amended soil; EC: electrical conductivity;OM: organic matter; 1metal extracted by aqua regia.

82 F. de Andrés et al. / Science of the Total Environment 378 (2007) 81–83

metal contents were below the recommended values foragricultural use by Spanish legislation (R.D.: 1310/1990). The biosolids (B) were applied at two rates, 0 and40 Mg ha−1, and incorporated with a chisel plough.These treatments were replicated four times in a ran-domised complete block design. The individual plotsmeasured 36 m2. Four months later (autumn), fourspecies of wild leguminous shrub (Colutea arborescens,

Dorycnium pentaphyllum, Medicago strasseri and Re-tama sphaerocarpa) were planted (planting distance1.5 m×1.5 m).

The survival and the height of the shrubs were deter-mined 12 and 24 months after planting. The above-ground biomass production of the spontaneous herba-ceous vegetation was determined 24 months after theapplication of the biosolids by harvesting four randomlyplaced 0.5 m2 quadrats in each treatment plot. Thismaterial was oven-dried at 60 °C until a constant masswas obtained.

Soil samples for each replicate were collected fromthe surface (0–30 cm) at before planting and 12 and24 months after planting. The samples were air-dried,passed through a 2 mm sieve and analysed according tothe standard soil test laboratory procedures of theSpanish Ministry of Agriculture, Fishing and Food(1994). ANOVA (SAS Institute, 2001) was used tocompare the results of the amended and control plots (C).

3. Results and discussion

Fig. 1 shows the survival percentage (1.a) and theheight (1.b) of the four wild leguminous shrubs. Theapplication of biosolids slightly reduced their percent-age of survival. At 24 months, the survival of the fourspecies studied was on an average 20% lower than in thecontrol plots: the survival of Dorycnium pentaphyllumand Retama sphaerocarpa was normal (no significantdifferences between the treatment and control plots), but

Fig. 2. Herbaceous biomass production (g/m2) in the second year onthe biosolid-amended (B) and control soils (C).

83F. de Andrés et al. / Science of the Total Environment 378 (2007) 81–83

that of Colutea arborescens and Medicago strasseriwas respectively 50% and 20% lower than in the Cplots.

The average height of the four wild shrubs increasedby the addition of the biosolids (Fig. 1b); all weresignificantly taller (a mean of 1.5 times taller) whengrown on the amended soil. Several factors may havecontributed to this, especially the increased supply of N,P, and K (Table 1). However, an improvement in thesoil's physical and biological properties cannot be ruledout. Biosolids undoubtedly added organic matter, in-creasing the soil's water-holding capacity, decreasing itsbulk density, increasing aeration and root penetrabilityand stimulating its microorganisms activity (Gusquianiet al., 1995).

After 24 months the average production of sponta-neous herbaceous biomass was greater on the amendedsoil (Fig. 2). This increase can be attributed directly to arise in soil fertility, yet this may have been responsiblefor the reduction in the survival the shrubs: the rapidgrowth of spontaneous vegetation may have led to watercompetition. However, the high production of biomass

would increase the pool of organic matter in the soil, andits slow turn-over would increase the probability ofnutrients being retained in the system. This would resultin increased nutrient cycling potential, which, in thelong term, might promote soil recovery and contribute tothe successful establishment and growth of the plantedleguminous shrubs.

4. Conclusion

The successful establishment and growth of the fourleguminous shrubs on the biosolid-amended soil, plusthe increased production of biomass by the spontaneousvegetation, suggests this approach may be feasible forthe rehabilitation of abandoned agricultural land andhelp reduce its erosion by water.

Acknowledgements

This research was partially supported by the INIA(RTA 01-078-C2-1).

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