Impact of harvest residues, fertilisers and N-fixing plants on growth and nutritional status of young Eucalyptus globulus plantations, under Mediterranean conditions

Abstract

Growth and nutritional status of young plants of Eucalyptus were assessed in a field trial, under different scenarios of harvest residue management and nutrient availability. Treatments were as follows: incorporation of harvest residues into the soil by harrowing (I); I with N fertiliser application (IF); I with leguminous, Lupinus luteus L., seeding (IL); removal of harvest residues (R); R with N fertiliser application (RF); R with leguminous seeding (RL); distribution of harvest residues on the soil surface (S); S with N fertiliser application (SF). Treatments were replicated four times in four blocks with a fully randomised design. Tree growth (height and diameter at breast height) was measured and understory biomass destructively recorded. Tree nutritional status was assessed by foliar analysis (N, Ca, Mg, P, K and leaf area). Significant differences in growth between I, R and S treatments were only detected at early stage. Intercropping with Lupinus decreased tree growth during the early phase, but after 5 years growth was similar to that measured in the I and R treatments. Application of fertiliser enhanced tree growth especially when harvest residues were retained on the soil surface. Combining incorporation of harvest residues with fertiliser application (IF) was the best option to increase tree growth, which was significantly greater than in the R and S. Initially, leaf N was positively affected by the leguminous (RL and IL), but, after the first fertiliser application (1 year after planting), greater N was observed in the IF, RF and SF, the difference decreasing gradually over the following years.

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

“…At short term, harrowing led to a decrease in soil bulk density and therefore to an alleviation of soil compaction, following results reported by Madeira et al (1989Madeira et al ( , 2010 for the effects of harrowing regarding forest plantations installation. The short-term recover of higher values of soil bulk density may be associated with the low soil organic C content and the low amount of understory (lower than in the C and F treatments), which are the major factors to maintain or enhance low soil bulk density, as reported by Celette et al (2005).…”

“…These results are in agreement with those reported from an experimental trial in which optimum fertiliser application for a 6-year period only slightly increased tree growth (Pereira et al 1994) and from another experiment in which total removal of organic residues (forest floor litter layer and harvest residues) did not significantly affect tree growth (Madeira et al 2004). Also, similar results were observed with heavy fertiliser application during the first 3 years after planting in the presence or absence of harvest residues (Madeira et al 2010). This trend has been associated with the Mediterranean climate conditions (dry sub-humid), which determine that tree productivity is strongly affected by water availability and, at lower extent, by nutrients (Pereira et al 1994).…”

“…Within the context of this study and due to the characteristics of dry sub-humid Mediterranean climate, such disturbance may also be favourable for decreasing fuel load and fire risk. However, the understory amounts measured in the present study are much lower than in the early plantation stages (Madeira et al 2010), suggesting that their contribution to fuel load is much lower than that of soil organic layers and, therefore, negligible. Low understory amounts also suggest a low competition of understory for water and nutrients, which is in conformity with the similar soil water and nutrient status in harrowed and non-harrowed treatments.…”

“…This trend is not in conformity with the harrowing positive effect on initial eucalypt seedlings growth, which may be related to the different development of root system along the soil profile (Madeira et al 2010). This may be associated with the fact that early seedling root development beneficiates of compaction alleviation by harrowing, while 5 years later it may be jeopardised by that mechanical operation.…”

Analysis of the Impact of the Use of Eucalyptus Biomass for Energy on Wood Availability for Eucalyptus Forest in Portugal: a Simulation Study

“…If harvesting residues are left on the soil, nutrient removal is reduced, and they also help protect against soil erosion. Even though recent studies have shown that, for Mediterranean conditions, retaining harvest residues on the soil surface does not increase tree growth compared with removing it (Jones et al 1999, Madeira et al 2010, only the incorporation of harvest residues, despite the negative effects caused by harrowing, show a positive effect on tree growth (Madeira et al 2010). In turn, bioenergy plantations (Source Energy ) were assumed to be more intensively managed than pulp stands (see Table A.2 in the Appendix) based on the type of management practiced for willow (Salix sp.)…”