The development of agriculture in South China in Song Dynasty?

During the Song Dynasty, northerners moved south, bringing a large number of labor and advanced production technology. The rapid development of agricultural production in South China benefits from the improvement of farm tools in paddy fields, the maturity of agricultural farming techniques and the popularization of rice-wheat rotation. The pressure of population growth has promoted the reclamation of a large number of cultivated land, and people have opened polder fields, sand fields and terraces according to local conditions. The area of rice fields has increased rapidly.