The precipitation in Korea is heavily concentrated in summer. About 70% of the rain falls during the period of June through September. Annual precipitation varies from 500 mm in the northern inland to 1,400 mm on the south coast. The number of frost-free days ranges from 169 to 228 days. Climatic conditions of the Korean peninsula in general are suitable for the cultivation of soybeans. There are diversified cropping systems of soybeans in Korea like as continuous cropping, crop rotation, intercropping, relay-intercropping, alternate cropping, and border cropping. The main cropping system in 1970s was barley-soybean. Recently, the cropping systems of tobacco-soybean, onion-soybean, and garlic-soybean were increased.