Biomass production assessment from Populus spp. short-rotation irrigated crops in Spain

The aim of this study was to evaluate the biomass production potential for the Spanish Iberian Peninsula using the Populus spp. 'I-214' clone under several management regimes and land availability scenarios, and to determine its future contribution to Spanish energy demands. Empirical models were fitted to the data from a network of 144 plots located at 12 sites in the continental Mediterranean climatic regions of the Iberian Peninsula, in which yield was related to climate and soil, as well as to plantation management variables. Four models were developed considering average maximum temperature of the hottest month (T-MAXH, degrees C), length of drought (A, months), intensity of drought (K, unitless) and soil pH. Predictions were made for the irrigated agricultural land (IAL), where the value of the independent variables were within the validity range, and for two management scenarios. Energy production capacity was evaluated by considering the alternatives for transforming poplar SRC biomass: heat, bio-ethanol and electricity. The results indicated a mean productivity for the Spanish Iberian peninsula of between 15.3 and 10.9 Mg ha(-1) yr(-1) for the standard management scenario and the poorly irrigated and weeded management scenario respectively. Two IAL scenarios were considered for the calculation of biomass production potential: all IAL for which it was possible to make predictions is made available for poplar SRC (TP, maximum hypothetical production capacity), and another in which only unproductive IAL is available for poplar SRC (RP, production capacity without constricting agricultural production). The TP scenario contributes up to 6.8-9.6% of total energy demands, and the RP scenario 0.7-0.9%, depending on plantation management.