Environmental impact of different agricultural production systems

ABSTRACT The efficient use of natural resources in production systems is essential for achieving ecological balance and sustainability in these systems. Current agricultural production systems have intensified the use of fertilisers and pesticides that contribute to an increase in energy flow, accelerating the process of degradation. The aim of this study was to evaluate, using emergy analysis, the environmental performance of different irrigated production systems for different sources of water, energy and fertiliser, and of rainfed systems under different types of soil preparation. The irrigated systems were studied in the experimental area of the Sewage Treatment Station (ETE) in Tianguá, Ceará (CE), and the rainfed models at the Fazenda Normal Farm in Quixeramobim, CE. Emergy analysis basically consists of three stages: construction of the systemic energy flow diagram, elaboration of the emergy evaluation table, and calculation of the emergy indicators. A mean value of 0.04 was found under the rainfed production systems, which shows less environmental stress compared to the irrigated systems, 0.30. The influx of economic resources into agricultural systems increases the environmental load and reduces renewability. Treated domestic effluent and photovoltaic solar energy afforded an increase in emergy yield and in the environmental sustainability of the production models.

摘要 生产系统中自然资源的高效利用，是实现此类系统生态平衡与可持续发展的核心前提。当前农业生产系统过度使用化肥与农药，导致能流攀升，加速了生态退化进程。本研究旨在通过能值分析（emergy analysis），评估不同水源、能源与化肥配置下的各类灌溉生产系统，以及不同整地模式下雨养农业系统的环境表现。灌溉系统的试验研究设于巴西塞阿拉州（Ceará, CE）蒂瓜市的污水处理站（Sewage Treatment Station, ETE）试验区，雨养农业模式的试验则在该州奎克萨莫比姆的法曾达常规农场（Fazenda Normal Farm）开展。能值分析主要包含三个步骤：构建系统能流图、编制能值评估表以及计算能值指标。研究结果显示，雨养农业系统的平均能值指标为0.04，相较于灌溉系统的0.30，其面临的环境压力更低。农业系统中经济资源的流入会提升环境负荷并降低系统可再生性。生活污水处理后出水与光伏太阳能的应用，可提升生产模式的能值产出与环境可持续性。