Sewage sludge stabilisation and fertiliser value in a silvopastoral system developed with Eucalyptus nitens Maiden in Lugo (Spain)

Abstract

Copper (Cu) is one of the heavy metals with highest proportion in sewage sludge. In Europe, sewage sludge should be stabilised before using it as a fertiliser in agriculture. Depending on the stabilisation process, sewage sludge has different Cu contents, and soil Cu incorporation rates. This study was undertaken to examine the effect of fertilisation with different types of sewage sludge (anaerobic, composted, and pelletised) on the concentration of total and available Cu in the soil, the tree growth, the pasture production, and the concentration of Cu in the pasture when compared with control treatments (i.e. no fertilisation and mineral fertilisation) in a silvopastoral system under Eucalyptus nitens Maiden. The results of this experiment show that an improvement of the soil pH increased the incorporation and the mineralisation of the sewage sludge and litter, and therefore, the release of Cu from the soil. Moreover, the concentration of Cu in the pasture and the levels of Cu extracted by the pasture improved when the soil organic matter decreased because the high levels of organic matter in the soil could have formed Cu complex. The composted sewage sludge (COM) increased a) the soil variables studied (pH, total Cu, and available Cu) and b) the Cu extracted by the pasture, both probably due to the higher inputs of cations made with it. In any case, the levels of Cu found in the soil never exceeded the maximums as set by Spanish regulations and did not cause harmful effects on the plants and animals. Therefore, the use of COM as an organic fertiliser should be promoted in silvopastoral systems established in edaphoclimatic conditions similar to this study because COM enhanced the productivity of the system from a viewpoint of the soil and the pasture, without causing any environmental damage.

Anaerobic digestates from sewage sludge used as fertilizer on a poor alkaline sandy soil and on a peat substrate: Effects on tomato plants growth and on soil properties

“…Soil analysis results revealed a change in soil pH after the treatments application. Many works reported an increase (Bayoumi Hamuda et al, 2009;Ferreiro-Domínguez et al, 2011) or a decrease (Mosquera-Losada et al, 2016;Singh and Agrawal, 2007) in soil pH. In the present work, acidification occurred in treated sandy soil samples, probably due to both the lower pH of SSADs and the nitrogen mineralization (Rasouli-Sadaghiani and Moradi, 2014).…”

Municipal sewage sludge compost promotes Mangifera persiciforma tree growth with no risk of heavy metal contamination of soil

“…Several soil properties, such as bulk density, porosity, and water-holding capacity showed improvement because of the addition of SSC 38 – 40 . SSC can also play an important role in regulating soil pH 22 , 41 . In general, the changes in the physicochemical parameters of soil became more pronounced with increasing rates of SSC application 40 .…”

“…The positive influence of the application of SSC on soil properties generally resulted in a positive effect on the growth and nutrient uptake of a wide variety of plants 4 , 40 , 41 . Several studies have reported better growth for different woody plants following the application of SSC, including Larix decidua 43 , Paeonia suffruticosa 9 , and Pinus radiata 44 .…”

Global Evolution of Research on Silvopastoral Systems through Bibliometric Analysis: Insights from Ecuador

“…In relation to economics, we observed a study focused on analyzing the environmental and economic profitability of livestock grazing on farms under a silvopastoral system [79]. Finally, the most relevant species were Quercus ilex, Quercus rubra, Pinus radiata, Fraxinus excelsior, Prunus avium, Pinus pinea, Eucalyptus nitens, and Betula pubescens [79][80][81][82][83][84][85].…”