Balanço emergético de diferentes sistemas de produção agrícola na região nordeste do Brasil

Abstract

The resources water and energy are factors fundamental in the development of agricultural production systems. The use efficient of these resources is crucial to achieving the ecological balance and sustainability of the productive system. Current production systems have intensified the use of fertilizers, pesticides, fuels and mechanization, which contributes to increased energy flow, accelerating the degradation process. The aim of this study was to evaluate the emergy balance of different irrigated production systems in function of different sources of water, energy and fertilizing compared to different production models in the rainfed. The study of irrigated production models was conducted in the experimental area of the Sewage Treatment Station (ETE) in Tianguá - CE and the Curupati Irrigated Perimeter in Jaguaribara - CE. The alternative production models proposed for rainfed agriculture the research was carried out at the Normal Farm EMATERCE in Quixeramobim - CE. The emergy analysis consists basically of three steps: construction of the systemic diagram, elaboration of the table of evaluation of emergy and the calculation of the emergy indicators. The rainfed production system showed an emergy value of 1.06E+16 seJ ha-1 year-1, being lower than in the irrigated system 1.69E+17 seJ ha-1 year-1. It was verified that the systems of production with wastewater and photovoltaic solar energy (S2A0, S2A1 and S2A2) presented better rates of emergy yield in relation to the conventional irrigated systems (S1A0, S1A1, and S1A2) and in comparison to the crops in the rainfed (T-PC, T-ESS, T-CSS and T-CCO). The conventional irrigated agricultural systems and the rainfed production system shown highly dependent on economic resources (materials and services). The rainfed production systems presented better emergy balance in relation to irrigated crops. The input of resources from the economy into agricultural systems increases the environmental impact and reduces renewability. The renewable production systems showed better performance in all components of cowpea production and the use of treated sewage in irrigated crops can satisfactorily replace the mineral fertilizing of the crop.