Relating energy performance and water productivity of sprinkler irrigated maize, wheat and sunflower under limited water availability

The energy potential of a crop may be evaluated through life cycle assessment methodologies. These refer to the computation of the crop’s energy balance and related indicators, such as the energy efficiency. This study concerns sprinkler irrigated sunflower, wheat and maize crops using data relative to the campaign of 2008. It is applied to selected farms in the Vigia Irrigation District, Alentejo, using pressurised water distribution systems. A model was developed and various scenarios were considered in order to assess the impacts on the crops’ energy balance of (1) full and deficit irrigation, (2) climatic demand scenarios, and (3) upgrading irrigation systems performance. The model allows the energy efficiency and the energy balance of the three referred crops using centre-pivot and solid set sprinkler systems to be computed. The different irrigation scenarios and crop yield thresholds were defined in a previous study (Rodrigues & Pereira, 2009). The modelling results lead to the conclusion that the maize crop is the most efficient in producing energy and wheat is the least for all the alternative scenarios considered. The results of full irrigation scenarios present higher energy performance than deficit irrigation because it depends greatly on the yields achieved. Weak relationships were found when relating energy efficiency and water productivity (WP) because while the first mainly depends upon yields, the second is highly influenced by water use. Results also show that improving irrigation systems performance has little impact on energy performance, which contrasts with WP.