A farmer drives a tractor to plant corns in the field in Shuangcheng District of Harbin, northeast China's Heilongjiang Province, April 20, 2020. Spring sowing in Heilongjiang Province has started recently. (Xinhua/Wang Song)

A farmer drives a tractor to plant corns in the field in Shuangcheng District of Harbin, northeast China's Heilongjiang Province, April 20, 2020. Spring sowing in Heilongjiang Province has started recently. (Xinhua/Wang Song)

Farmers drive tractors to plant corns in the field in Shuangcheng District of Harbin, northeast China's Heilongjiang Province, April 20, 2020. Spring sowing in Heilongjiang Province has started recently. (Xinhua/Wang Song)

A tractor plants corns in the field in Shuangcheng District of Harbin, northeast China's Heilongjiang Province, April 20, 2020. Spring sowing in Heilongjiang Province has started recently. (Xinhua/Wang Song)

A farmer drives a tractor to plant corns in the field in Shuangcheng District of Harbin, northeast China's Heilongjiang Province, April 20, 2020. Spring sowing in Heilongjiang Province has started recently. (Xinhua/Wang Song)

Farmers drive tractors to plant corns in the field in Shuangcheng District of Harbin, northeast China's Heilongjiang Province, April 20, 2020. Spring sowing in Heilongjiang Province has started recently. (Xinhua/Wang Song)