The use of municipal sewage sludge as a fertiliser could be a more adequate
means of disposal of this residue than its transport to the dump. The obje
ctive of this experiment was to evaluate the effects of different doses of
sludge and sowing a mixture of cocksfoot (Dactylis glomerata) and clover (T
rifolium repens) on pasture production, botanical composition of the pastur
e, forage quality, and changes in soil chemical properties. Treatments appl
ied were: (1) no fertilisation (L0), (2) fertilisation with 26 Mg ha(-1) of
sewage sludge with no sowing (L40), (3) fertilisation with 26 Mg ha(-)1 of
sewage sludge and sowing with 25 kg of Dactylis glomerata L. cv Artabro (D
g) and 3 kg Trifolium repens cv Huia per hectare and (4) 52 Mg ha(-1) of se
wage sludge with no herbage sowing (L80). Plots were established in a silvo
pastoral system with Pinus radiata D. Don at a density of 1666 trees ha(-1)
(3 x 2 m). The improvement of soil fertility due to organic fertiliser app
lication and the use of Dactylis glomerata increased the production and qua
lity of pasture as well as reduced the risk of fire and erosion, as grasses
dominated shrubs. Fertilisation with sewage sludge in soils of acid origin
increased the concentration of copper in the pasture and, if cocksfoot was
not sown, the levels of this element exceeded the maximum tolerable dietar
y levels for sheep. On the other hand, fertilisation also increased the lev
els of zinc in pasture, but values were not above toxic limits for sheep, h
orses and cattle.