中文摘要：

尽管中国实行了世界上最严格的耕地保护制度，但耕地数量仍不断减少，并将在今后一段时间内呈减少趋势，在一定程度上威胁了我国的粮食安全。提高土地利用效率是保障我国粮食安全的一条重要途径。本文选取耕地复种指数和土地综合产出率两个指标来表示农户土地利用效率，利用江苏省南京市274个农户的实地调查数据．运用多元线性回归模型对土地细碎化、农地流转对农户土地利用效率的影响进行了实证研究。模型估算结果表明：土地细碎化导致农户复种指数的下降，并阻碍了平均土地综合产出率的提高；转出土地的农户的复种指数和平均土地综合产出率要低于没有转出土地的农户，而转入土地农户的平均土地综合产出率要高于没有转入土地的农户。因此，建议通过推进土地流转来提高土地利用效率。

英文摘要：

In recent years, China has implemented the most rigorous institutional system for protection of cultivated land in the world, but vast amounts of arable land have been used for non-agricultural purposes, and cultivated land will continue to decrease, creating a threat to food security. China must depend on its own arable land to feed its large population. In order to safeguard food security, we should take some measures to enhance land use efficiency. Land fragmentation may constitute a major obstacle to increasing land use efficiency, while land transfer can enhance farmers＇ land use efficiency. In this article, we use a multi-cropping index and data on average grain yield per unit area to characterize land use efficiency. The analysis is based on a survey of 274 rural households in three counties： Jiangning, Luhe, and Lishui, all administered by the city of Nanjing in Jiangsu Province. In these samples, there are 144 households involved in arable land transfer： 33 households rent in, and 111 households rent out their land. Land fragmentation is also very serious in the study area. This paper applied detailed household data and used multiple linear regression analysis to investigate the impact of land fragmentation and land transfer on land use efficiency. The quantitative results showed that land fragmentation had a negative impact on the multi-cropping index and average grain yield per unit area. Farmers who rent out their land had a lower multi-cropping index and average grain yield per unit area, while farmers who rent in land had a higher average grain yield per unit area. In addition, the ratio of non-agricultural income to household income was found to positively affect multi-cropping index and average grain yield per unit area. The proportion of dry land to total cropland had a negative impact on multi-cropping index, and total household income had a negative impact on average grain yield per unit area. With existing technologies, increasing the prevalence of land transfer may be an important optio