Do harrowing and fertilisation at middle rotation improve tree growth and site quality in Eucalyptus globulus Labill. plantations in Mediterranean conditions?

Abstract

Effects of harrowing and fertilisation on tree growth, understory vegetation, forest floor litter and soil properties were studied in a field experiment installed in a 5-year-old first rotation eucalypt plantation. The treatments were harrowing (H), fertilisation (F), harrowing and fertilisation (HF) and a control without any treatments (C), with four replicates. Tree growth, root mass, tree nutrition status, understory vegetation, mass of forest floor litter and soil physical and chemical properties were monitored till the end of the rotation (stand was 14-year old). Effects of treatments on tree growth, root mass and timber production were not significant. Root nutrient concentration differed between treatments only few months after the beginning of the experiment, while differences regarding specific root length and area were observed during the first year. Harrowing (H and HF) led to significantly smaller biomass of understory vegetation (\13.4 g m -2 ) than other treatments (33-61 g m -2 ) during the first 3 years, but at the end of the experiment differences were less important. Forest floor litter mass after 3 years and at the end of the experiment were similar among treatments. Soil bulk density significantly decreased by harrowing (H and HF treatments), but 16 months after treatments were similar. Although soil chemical properties were not significantly affected by treatments, a decrease in base cations occurred during the rotation period. Fertiliser application is a questionable practice under the economic point of view, whereas harrowing can reduce the fuel load only during a short period, without negative effects on productivity and soil quality.

Nutritional Prescriptions for Eucalyptus Plantations: Lessons Learned from Spain

“…These authors tested different combinations of NPK in southeast Spain and found that tree growth in sandy soils (fertilizer application in a five-year-old E. globulus plantation) was significantly enhanced by addition of N. In soils over slates (fertilizer application in a seven-year-old E. globulus plantation), the trees responded to fertilization with N and K [68]. However, these proposals are controversial, as different results were obtained in fertilization trial in five-year-old E. globulus plantation in central Portugal, where Madeira et al [69] reported no positive response to fertilizer application for a cutting cycle of 14 years. The authors suggest that fertilizer application may be useful for enhancing soil quality and ensuring the long-term sustainability of eucalyptus plantations.…”