Why is China's triple superphosphate (TSP) capacity concentrated in Yunnan and what drives its export orientation?

Why is China's triple superphosphate (TSP) capacity concentrated in Yunnan and what drives its export orientation?
China's effective TSP capacity stands at about 2.9 million tonnes, with Yunnan accounting for over 75% of the total. Leading producers include Chuan Jinnuo and Yunnan Xiangfeng, with Chuan Jinnuo running at over 180% of its 290,000-tonne design capacity. Roughly half of China's TSP output is exported, primarily to Indonesia, Australia, Japan, Brazil, and New Zealand. Domestic consumption of TSP is less than 10% of total phosphate fertilizer use, as Chinese farmers prefer ammonium phosphates. The product's high P2O5 content (40-50%) and low heavy metal levels make it competitive globally. The domestic-export price gap has been extreme, with Moroccan FOB prices exceeding RMB 7,000/tonne versus around RMB 3,200/tonne domestically, incentivizing producers to prioritize overseas sales.