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

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 year