Emergy analysis of vegetable ecosystem in Pei County, Jiangsu Province

The theory of emergy analysis is based on the premise that all forms of energy are from the sun. Different and incomparable forms of energy are therefore unifiable into solar emjoules. In this study, environmental resources and economic characteristics of vegetable ecosystems in Pei County (one of the main production bases of vegetable in Jiangsu Province) were quantitatively analyzed using the theories and methods of ecosystem emergy analysis. A series of emergy indices were developed for evaluating the environment resources and development characters of the vegetable ecosystem in Pei County. These indices simultaneously provided scientific basis for sustainable development of vegetable industry in Pei County. The study showed that: in 2007, vegetable emergy input in Pei County was 1.22×10²¹ sej. Industrial auxiliary energy input was 7.18×10²⁰ sej, accounting for 58.85% of the total vegetable ecosystem emergy, which suggested that the development of vegetable industry in Pei County relied mainly on industrial auxiliary energy, and had developed beyond traditional agriculture relied mainly on natural conditions. Vegetable ecosystem output in Pei County was 3.20×10²¹ sej, accounting for 39.65% of total agriculture emergy yield, indicating that vegetable industry was one of the strongest pillars of industries in Pei County. Emergy outputs from solanaceous fruits and roots, tuber vegetables were relatively higher, accounting for 35.63% and 23.63% of total vegetable emergy yield, respectively. Foreign exchange earning vegetables such as burdock and Chinese yam accounted for 18.61% of total vegetable emergy yield. Emergy self-sufficiency ratio of vegetable ecosystem in Pei County was 2.67%, which was lower than that of arable land ecosystems of Jiangsu Province (10.12%), illustrating that environmental resources were no longer the main determinants of vegetable development. The resistance of vegetable ecosystem in Pei County to natural disasters was sufficiently strong. The proportion of industrial auxiliary emergy of vegetable ecosystem in Pei County was 58.85%, which was lower than that of arable land ecosystems in Jiangsu Province (73.16%). There was a huge consumption of chemical fertilizers in vegetable production in Pei County, accounting for 69.42% of industrial auxillary emergy. This was considered unfavorable to sustainable development of vegetable industry in the county. Organic auxiliary emergy ratio of vegetable ecosystem in Pei County was 38.61%, which was higher than that of arable land ecosystems of Jiangsu Province (16.72%). Purchased emergy ratio of vegetable ecosystem in Pei County was 97.54%, which was higher than that of arable land ecosystems of Jiangsu Province (89.88%), suggesting that the development of vegetable industry in Pei County almost totally depended on buying emergy of the socio-economic system. The high emergy purchase promoted rapid development of vegetable industry in Pei County. Emergy investment ratio of vegetable ecosystem in Pei County was 36.61 and that of arable land ecosystems in Jiangsu Province was 8.88. This further suggested a rapid development of vegetable industry in Pei County. However, net emergy output ratio of vegetable ecosystem in Pei County was only slightly higher than that of arable land ecosystems in Jiangsu Province. This was due to insufficient promotion of high output new technologies. Environmental loading ratio of vegetable ecosystem in Pei County was 1.43, which was lower than that of arable land ecosystems in Jiangsu Province (2.83). Pesticide input only accounted for 0.21%, indicating that vegetable industry in Pei County was strongly sustainable with a high development potential. Further strengthening of vegetable industry infrastructure would enhance comprehensive benefit and sustainable development of county-level vegetable industry. It was also recommended that the development of vegetable processing industry and popularization of science and technology should be enhanced, which could benefit emergy output increase of vegetable ecosystem in Pei County.