wAbstract
@The aim was to study the influence of soil properties on the
leaching of nitrate, phosphate and organic matter (OM) following
the application of sewage sludge to contrasting soils. Seventy
agricultural soils from different parts of Spain were amended
with sewage sludge (50 t dry weight ha-1), and a controlled
column study was developed. After 2, 4 and 6 months of incubation,
distilled water, equivalent to an autumn rainfall event of 25
lm-2 in Mediterranean environments, was applied and leachates
collected and analysed: pH, electrical conductivity (EC), chemical
oxygen demand (COD), phosphate and nitrate. The mean values of
pH in the leachates after 2, 4 and 6 months were similar and close
to the neutrality. The highest concentrations for the rest of
the parameters analysed were found after 2 months of incubation
and diminished for 4 and 6 months, especially COD. Soil pH and
texture were the most relevant soil properties controlling the
leaching of the analysed parameters. The OM mineralization seemed
to be enhanced at high values of soil pH, thus increasing the
nitrate and reducing the COD leaching. However, phosphate levels
were reduced at high values of soil pH. In addition, leaching
was promoted in sandy soils. Other soil properties influenced
phosphate leaching being the equivalent calcium carbonate soil
content as the most relevant. Soil organic carbon was negatively
related to the EC and nitrate concentration in the leachates but
resulting in a weak contribution compared with soil pH and texture.
Concerns about nitrate pollution have been confirmed.
Keywords: Chemical oxygen demand (COD); Mobility; Nitrate; Phosphate;
Sewage sludge; Soil propertiesx
1. Introduction
2. Material and methods
@2.1. Soil and sewage sludge samples
@2.2. Column study
@2.3. Statistical analysis
3. Results
4. Discussion
@4.1. Leachates characteristics
@4.2. Influence of the soil properties on the leaching of the
different parameters
5. Conclusions
Acknowledgements
References