Abstract: Cultivated land is fundamental to the sustainable development of Chinese agriculture, society and economy. Rapid industrialization and urbanization has worsened the situation of the scarce cultivated land resources. It's therefore very important for agricultural ecological civilization and sustainable development based on the evaluation on cultivated land use efficiency. Energy provides a new measure for evaluating environment, resources, human services, information, and alternatives for development. In this paper, taking cultivated land in Wuxue as an example, the calculating method and spatio-temporal varyingn characteristics of utilization efficiency for cultivated land were built and analyzed based on the connotation defining of efficiency of cultivated land and Energy Theory provided by H. T. Odum. The results showed that: 1)The input and output energy of cultivated land were on the rise in the 10 years during 2002-2011 and the growth rate reached 58.17% and 62.19% respectively. Among the various parts of inputs energy, industrial energy accounted for the largest (more than 70% of the total), even increased by 82.17% in 2011. 2) Cultivated land eco-economic system in Wuxue was cost-efficient and the degree of land use intensity was increasing every year. The degree of input energy density was 2.35×10¹⁶ sej/hm² in 2011, being much higher than in 2002, but the output-input ratio based on energy took on the trend increased first (2002-2005) and decreased afterwards (2006-2011). Energy-based resource and environmental loading index of cultivated lands was on the rise from 2.88 to 4.61 in 10 the years during (2002-2011), the deteriorating quality of cultivated land threatens ecological environment, food security and sustainable agricultural development. 3) The energy per farmer was increasing year by year from 2002 to 2011. In 2011, the energy per farmer reached 6.08×10¹⁵ sej, increased by 53.92%, indicating a greatly improved living index of farmer. The growth rate of the energy per farmer year on year was however unstable. The output of energy density presented an inverted "V" shape as a general from 2002 to 2011. There has been a slowly declining trend since 2008, indicating a serious problem of grain security. 4) The results Moran's I indicated that the input and output energy for unit area of cultivated land in Wuxue has a gathereing characteristics. From the results, it is expected to provide a reference for optimizing the input structure in agricultural production and the further improvement to develop sustainable productivity of cultivated land.

Key words: utilization efficiency, spatio-temporal characteristic, emergy analysis, cultivated land