Rotation length of intensive Eucalyptus plantations: How it impacts on productive and energy sustainability

Abstract

The identification of optimal rotation length of forest crops considering production and environmental perspectives is a major concern for eucalypts since plantations costs are high and nutrient extraction is considerable. This study assessed biomass productivity, energy yield and nutrient use efficiency of E. benthamii,E. dunnii and E. grandis plantations for energy purposes, with densities of 2220, 3330, 4440 and 6660 trees.ha−1 in the first rotation during a period of 76 months. Weight, content and extraction of nutrients, energy yield and efficiency of the use of nutrients in conversion to biomass and energy were measured in the stem with bark. The results showed a stabilization of biomass production, energy yield, and nutrient conversion efficiency between 49 and 57 months of age for all species and planting densities. During this time range, biomass productivity was notoriously reduced at higher planting densities (6660 vs. 2220 trees.ha−1), showing the convenience of using low densities. No relationship between productivity and efficiency of nutrient use was detected in the entire age range evaluated. E. benthamii and E. grandis were more efficient in converting nutrients to biomass and energy, while the three species showed similar productivity and energy yield. Productive and energetic sustainability can be enhanced by the optimization of rotation in eucalyptus crops in Uruguay.