CONICET | Buscador de Institutos y Recursos Humanos

The aim of this study was to evaluate the agroecosystems in the Pampa region (APR) using the energy synthesis that allows a common currency account in the consumption of goods from the economy and the environment. We analyzed two crops (maize and wheat-soybean double cropping) in three geographic areas during 2006 to 2010. Emergy indicators were calculated for 1) identifying temporal changes and 2) comparing the APR outcome with similar agro-ecosystems. The emergy synthesis showed no significant time-trend by analyzing the whole database. However, when data were analyzed by crop, the wheat-soybean showed significant increases in the use of external inputs (Pearson r = 0.55, P = 0.03) and transformity (Pearson r = 0.6, P = 0.01). Transformity is the emergy amount needed to obtain one unit of emergy product, so higher values correspond to lower emergy conversion efficiencies. When the overall performance of the APR were compared with similar agroecosystems, APR showed remarkably low value of transformity (i.e. high efficiency) which implies a nearly tenfold increase in emergy conversion efficiency compared with the less efficient system. Regarding the emergy yield return (EYR), the APR were able to capture, on average, 2.66 units of energy for every unit of energy invested, which is equivalent to 82% of what has been achieved in the agroecosystem with greater energy return system. The non-renewable to renewable emergy ratio (Environmental Loading Ratio, ELR) showed a value slightly less than 1 (0.96), being this value equivalent to 5% of the impact measured in the higher consumption of non renewable. These results suggest that APR could be considered among the more efficient and less environmental damage cropping systems of its kind. However, the wheat-soybean showed an increasing trend in the use of external inputs and decreasing efficiency (higher transformity values), which should be further monitored.