Liming and sewage sludge effects on soil fertility and understorey development in reforested Pinus radiata D. Don plantations

摘要

One of the main factor limiting pasture production in Galicia is the important tendency to acidity of its soils, which limits fertility and has made necessary the use of liming. On the other hand, fertilisation is an extended practice to improve forage biomass productivity to compensate for crop extractions, which can be done in an organic or inorganic way. The use of sewage sludge in forest lands is a good way to increase their potential productivity at low cost and limit its contaminant effect. Thecontaminant effect should be carefully evaluated in very acid soils due to the higher availability of heavy metals in very acid soils. The objective of the study was to evaluate the effect on Zn evolution (soil and pasture) and pasture production of theuse, on different dates, of liming and three sewage sludge doses and a no-fertilisation control in silvopastoral systems established in a very acid soil with Pinus radiata D. Don and after a pasture had been sown. The different results show that the application of lime and high doses of sewage sludge increased the Zn concentration in the soil, especially when the date of fertilisation was late.