## 5 Conclusions  
Our research showed that, in the suburbs of Shanghai, the expansion of the plot scale is restricted by various objective conditions, and the plot fragmentation pattern is inevitable and will exist for a long time. However, we are helpless in the face of large-scale farming. In fact, agricultural scale management has the characteristics of multiple spatial levels, such as the plot level, peasant household level, and city or regional level. Although we cannot realize centralized and contiguous land parcels in physical form, we can improve the degree of land parcel aggregation in property rights form by promoting the transfer of land parcel property rights to promote moderate-scale operation at the level of peasant households [85; 86], as well as to realize the centralization, intensification and specialization of regional agricultural production and management. We also found that there was an obvious trend of the dispersion of land use in the suburbs of Shanghai. From 1990 to 2018, the cultivated land area has been shrinking in suburban Shanghai, however, the agricultural households with appropriate operation scale and large-scale agricultural operation entities tend to increase in the number, show that under the background of plot fragmentation and land dispersion, moderate scale management of agriculture is still viable. In fact, there are three main ways in which to develop agricultural scale management: land centralized scale management, service centralized scale management and compound agricultural scale management [9; 10; 87]. It is difficult to eliminate the scattered and fragmented pattern of contracted land in the short term. Therefore, service scale management and compound agricultural scale management are the main remedies for future agricultural sustainable development. Future policy support should be focused on the scale of agricultural services and agricultural system innovations, strengthen the ability construction of agricultural social service systems, guide socialized service organizations to provide for pest control, fertilizer application, mechanized production, irrigation and drainage, storage and preservation services for family farms, break through the constraints of small-scale decentralized and fragmented land management on the development of modern agriculture [21; 88], develop agricultural stock cooperative systems, and promote diversification of agricultural business models. This study found that the total power of agricultural machinery is positively correlated with the cultivated land aggregation degree, but fixed asset investment, transportation construction, expansion of built-up areas, industrialization, service-oriented economy, urban population growth, economic development level, income level, and real estate development are negatively correlated with the cultivated land aggregation degree. Faced with the challenges of shrinking farmland, the ageing of the rural population and rising agricultural production costs, Shanghai should fully give play to the positive driving effect of agricultural mechanization on farmland aggregation degree, and rely on agricultural mechanization to improve the efficiency of land use; it should also encourage all kinds of talent to provide low-cost, convenient, and all-round technical services for agricultural producers and operators. It is gratifying that, under the dual strategic guidance of the strengthening of cultivated land resource protection and strict controlling urban growth boundaries, the permanent basic farmland distribution pattern in the suburbs of Shanghai will remain relatively stable, which laid a foundation for further improve the level of agricultural mechanization in Shanghai. The limitations of this study are as follows: (1) the selection of remote sensing images in different periods not only affects the accuracy of image interpretation, but also is closely related to the production cycle of crops.