Effect of lime and sewage sludge fertilisation on tree and understory interaction in a silvopastoral system

The productivity of the components of a silvopastoral system could be limited by the low soil fertility and the presence of shrubs in the land before planting. However, the understory vegetation can be modified by improving soil chemical properties when lime and organic fertilizers such as sewage sludge are applied. This study evaluated the effect of liming and the application of two doses of sewage sludge (50 kg total N ha−1 or 100  kg total N ha−1) on changes in soil chemical properties, tree growth and understory production as compared to the no fertilisation treatment in a silvopastoral system established in a reforested area with Pinus radiata D. Don. The results of this experiment show that the improved soil fertility caused by liming and fertilisation with sewage sludge modifies the proportion of the herbaceous/shrubs component in the understory, and promotes facilitation mechanisms which have a positive impact on the understory forage quality, tree growth as well as reducing fire risk.