Most eucalypt plantations are managed in short rotations (6–8 years) and are established in regions with water and nutritional stresses of varying degrees. The mean annual increment in these regions ranges from 20 to 45 m3 ha−1 y−1 depending on the level of environmental stress. Improving natural resource use efficiency by breeding and matching genotypes to sites and using appropriate site management practices is a key challenge to sustain or increase productivity. Climate change is emerging as a driving force behind many of the current issues facing natural resources, and is likely to intensify the water constraint. The Intergovernmental Panel on Climate Change has predicted significant increases in surface air temperatures and decreases in rainfall (with more erratic rainfall patterns) over the tropics and subtropics, affecting drier regions in particular. To be truly sustainable, forest management practices must be environmentally friendly, prevent or reduce land degradation, improve biodiversity and i...

Eucalyptus plantations have seldom responded to N fertilization in tropical and subtropical regions of Brazil. This implies that rates of N mineralization have been adequate to supply tree needs. However, subsequent crop rotations with low N fertilization may result in declining concentrations of organic and potentially mineralizable N (N₀), and consequent loss of wood productivity. This study investigated (a) in situ N mineralization and N₀ in soils of eucalypt plantations in São Paulo state, Brazil; (b) tree growth responses to N fertilizer applied 6–18 months after planting; and (c) the relationships between N_0, other soil attributes and tree growth. We established eleven N fertilizer trials (maximum 240 kg ha⁻¹ of N) in E. grandis and E. grandis x urophylla plantations. The soil types at most sites were Oxisols and Quartzipsamments, with a range of organic matter (18 to 55 g kg⁻¹) and clay contents (8% to 67%) in the 0–20 cm layer. Concentrations of N₀ were measured using anaerobic incubation on soil samples collected every three months (different seasons). The samples collected in spring and summer had N₀ 140–400 kg ha⁻¹ (10%–19% total soil N), which were best correlated with soil texture and organic matter content. Rates of in situ net N mineralization (0–20 cm) ranged from 100 to 200 kg ha⁻¹ year⁻¹ and were not correlated with clay, total N, or N₀. These high N mineralization rates resulted in a low response to N fertilizer application during the early ages of stand growth, which were highest on sandy soils. At the end of the crop rotation, the response to N fertilizer was negligible and non-significant at all sites.

Eucalypt plantations in Brazil have the highest mean productivity when compared to other producing countries, and fertilizer application is one of the main factors responsible for these productivities. Our aim was to identify appropriate rates of N, P and K in eucalypt plantations and their interactions with edaphoclimatic factors. Four trials with four rates and three nutrients (N, P and K) were set up. Each nutrient was studied separately, and the trees received sufficient rates of all of the other nutrients through fertilization, to avoid limitations not related to the desired nutrient. We assessed solid wood volume (SV), productivity gains (PG), leaf nutrient content and leaf area index (LAI) to determine the responses to fertilization. PG, regarding N, rates ranged from 104% to 127% at 60 months after planting. P fertilizer application led to gains in productivity in soils with levels of P-resin up to 5 mg·kg⁻¹, but decreased with stand age. K fertilizer application responses increased within age in three sites. In Paulistania, responses to K application were close to zero. N and K responses were climate related. Leaf nutrient content and LAI were not able to predict the highest yields obtained.