Sowing date of soybean (solar term)

There is a proverb in agriculture, "Before and after Qingming Festival, point melons and plant beans". Sowing date of soybean in spring mainly depends on soil temperature. Generally, sowing can be carried out when the soil temperature in 5cm is stable at 10- 12℃. April 5th is the Tomb-Sweeping Day in the twenty-four solar terms. When the sun moves to the longitude of the Yellow River 15 degrees, Tomb-Sweeping Day Qi begins. At this time, except the northeast and northwest regions, the average daily temperature in most parts of China has risen above 12℃, which is suitable for planting crops.