Destructive typhoons sometimes develop over the South China Sea during hot weather. Mean annual rainfall ranges from 1300 to 2300 mm. Rainfall is usually evenly distributed in June to October or November. October is the wettest month of the year. Total labor force is 35 million, with about 20 million engaged in agriculture.
Rice is the single most important crop.
In 1981, Vietnam departed from the collective agricultural production system by introducing the group-oriented contract system of production. That was changed to the individual contract, beginning in 1986. In 1989, Vietnam became a net rice exporter. Food grain production amounted to about 26.1 million t in 1995, of which rice accounted for 24.7 million t. There is a trend toward planting modern varieties, which offer high yield and are better adapted to the environment.