Energy efficiency and water use indices for sweet potato (Ipomoea batatas L.) production under subtropical climatic conditions of Bangladesh

For estimation of energy use efficiency for sweet potato production in the riverbank areas of Bangladesh under subtropical climatic conditions, a study was conducted with sweet potato producers of the respective areas from 60 individuals (12 producers' for each sweet potato variety) by using a structural questionnaire. The results revealed that the majority of the energy input was consumed by the pre harvest activities (22,313.55 MJ ha(-1) or 90.85%), of which fertilizer application (36.84%) and irrigation (35.24%) consumed the most energy input, whereas only 9.15% (2,248.42 MJ ha(-1)) consumed by the post-harvest activity for sweet potato production. The energy input involved in the production system was similar to the direct (12,149.76 MJ ha(-1) or 49.47%) and indirect (12,412.21 MJ ha(-1) or 50.53%) sources, while it was much higher in non-renewable sources (22,884.21 MJ ha(-1) or 93.17%) with a minimum of (1,677.76 MJ ha(-1) or 6.83%) from renewable sources. The average energy use efficiency, energy productivity, specific energy, net energy, energy profitability and water-energy productivity of orange -fleshed sweet potato (OFSP) varieties 4.36, 1.22 kg MJ(-1), 0.83 MJ kg(-1), 82,511.73 MJ ha(-1), 3.36 and 1.32 g m(-3) MJ(-1), respectively. The OFSP varieties showed better performance in respect of all the energy and water use indicators.