Agricultural production has entered a stage of moderate expansion.

During the period from 2004 to 2010, China's economy completed the leap to the turning point of Lewis (the turning point from surplus to shortage of labor). After a country's economy crosses the Lewis turning point, the relative scarcity relationship between capital and labor will change fundamentally, an important manifestation is that capital replaces labor more and more. In agriculture, where the labor force is relatively surplus, with the massive outflow of rural labor force, the resource endowment structure of agricultural production has also changed in recent years. In traditional agricultural production, the organization mode of replacing capital with labor has been gradually replaced by capital instead of labor, and has become an irreversible trend.

In this process, there is a problem that requires special attention. In agricultural production, the substitution of capital for labor does not necessarily lead to the improvement of labor productivity. On the contrary, if the capital inflow is not accompanied by the corresponding expansion of production scale, the substitution of capital for labor will lead to the waste of resources in the process of agricultural production. Specifically, the restriction of too small production scale on agricultural development is mainly shown in the following two aspects:

First, it restricts the application of advanced technology and the development of modern agriculture. In the actual production, there is a scale critical point in the application of agricultural technology. when the production scale of farmers is small, according to the principles of economy and rationality, farmers do not tend to adopt new technology, or even can not adopt "large-scale technology" alone. Therefore, under the condition that the scale of agricultural production remains unchanged, especially under the condition of agricultural production based on small farmers, the substitution of capital for labor is mainly manifested in the purchase of low-tech agricultural machinery, as well as the high-dose use of production factors such as pesticides, chemical fertilizers and herbicides. This still belongs to the extensive mode of agricultural production, which not only restricts the application of advanced technology and the improvement of agricultural production level, but also increases the possibility of agricultural production pollution.

Second, it has a negative impact on the structure of agricultural labor force. The scale of agricultural production is too small, it is difficult to improve agricultural production efficiency, agricultural efficiency is low, the ability, knowledge and young labor force will choose to leave the agricultural field and enter the secondary and tertiary industries. This makes the structure of agricultural labor force show the trend of aging and low skills. The development of modern agriculture needs corresponding modern agricultural production organizations and producers. In order to change the mode of agricultural production, we must first change the mode of agricultural production organization, cultivate and develop new types of agricultural operators, such as family farms, professional large households, farmers' cooperatives, leading enterprises and agricultural socialized service organizations, so as to form a new agricultural production service system. The aging and low-skilled agricultural labor force structure is obviously not conducive to agricultural development, especially to the market development of agricultural products and the use of new technologies, new varieties and new means of production. If the structure of agricultural labor force is not improved, the extensive mode of production of agriculture will be difficult to change, and the decline of agriculture and the decline of rural areas will be inevitable.

Therefore, the appropriate expansion of the scale of agricultural production is the key to ensure food security and achieve the healthy development of agriculture after crossing the Lewis turning point. To appropriately expand the scale of agricultural production is not to change the rural land contract relationship, nor to expand the scale of agricultural production blindly, but on the basis of natural economic conditions, the transfer of rural labor, the level of agricultural mechanization and other factors, reasonably determine the scale of agricultural production. On the basis of implementing the registration and certification work of confirming the right of land contractual management, through the orderly transfer of land management rights, the fine plots are concentrated in the hands of professional large households and other new types of agricultural operators to achieve appropriate scale of agricultural production. In our investigation, we found that once an appropriate scale of agricultural production is achieved, farmers' demand for fertilization technology, matching of improved varieties, cultivation techniques and advanced agricultural machinery and equipment will increase, and pollution sources such as chemical fertilizers, pesticides and plastic film will be more controllable. the unit cost of agricultural non-point source pollution will be reduced. This can not only improve the efficiency of the use of agricultural land, but also ensure that the income of large grain growers is basically the same as that of urban residents, increase farmers' income and attract more capable people to engage in agricultural production. With the realization of moderate scale operation of land and agricultural production, the social division of labor and specialized production will naturally develop, and a series of specialized production bases will be formed, which will further lay the foundation for increasing investment in science and technology and realizing standardized ecological production. form a virtuous circle of modern agricultural production.