Millions of migrant workers streaming back to China's industrial heartland after the long lunar New Year break face an uncertain future as smaller factories in particular struggle to cope with anaemic orders and rising inventories.

In the Pearl River Delta, the "world's workshop" in southern Guangdong province that accounts for around a quarter of China's exports, workers and business owners say production lines have been slower than usual to restart after the annual two-week holiday.

At the Xicheng industrial park in Hengli, several factories lay gutted with broken machines strewn outside, while plots of land earmarked for industrial use were being used by villagers to grow vegetables, a sign of the weak demand for Chinese goods that is forcing business closures and putting pressure on wages.