Short rotation coppice of leguminous tree Leucaena spp. improves soil fertility while producing high biomass yields in Mediterranean environment

Abstract

The use of woody nitrogen-fixing plant species as multipurpose and energy crops aims to enhance biomass yield while improving soil properties. Yet, the effectiveness of this option is still under debate especially the use of short rotation cropping in water and nutrient limited environments. This study investigated whether short rotation coppicing of four taxa of multipurpose biomass woody legume Leucaena spp. can improve soil conditions when grown for biomass under a Mediterranean environment. Biomass yield, mineral composition and heat value of the biomass and the mineral and organic matter content of soil were evaluated. Under favorable growing conditions, woody dry biomass production was up to 29 Mg ha-1 year-1 with slight but significant differences between the four taxa that were tested. After 11 years of cropping, the soil showed higher fertility and microbial activity compared to the uncropped plot. Leucaena cultivation increased soil nitrogen by 35 %, dehydrogenase activity by 98 %, and organic matter and carbon content (by 41 %). Annual cuttings resulted in the highest biomass production, followed by two and three year cuttings. The mineral composition and the calorific capacity of woody biomass make it suitable for commercial use as an energy source (generating on average 151 MW h ha- 1 year-1). In conclusion, short rotation coppicing of nitrogen-fixing woody species results in high biomass production rates with the restoration of degraded soils, constituting a sustainable agroforestry system for rural areas.