Glyphosate production is an integral cog in the economic engine of Chinas crop protection manufacturing base. The number and breadth of industries both foreign and international involved in its productions, distribution and transport cannot be understated, and for this reason the Chinese government is understandably protective of its interests.
Treading a dangerous line between outright anticompetitive behaviors and protection of its indigenous markets, the Chinese government has adjusted the export tax rebate on N-phosphonomethyl aminodiacetic acid (PMIDA), an important precursor chemical of glyphosate. The removal of the 13% rebate was pitched as an environmental initiative to protect Chinas phosphorus resources. But an ulterior motive for this move has a hugely significant and surely intended corollary effect: promoting the Chinese glyphosate industry.
http://www.farmchemicalsinternational.com/crop-inputs/why-glyphosate-prices-are-rising/
Glyphosate is Round Up. It is the chemical that strains of GMO corn are genetically modified to withstand. So China sell us tons of glyphosate then bans the importation of certain glyphosate dependent crops.
In a related story, the huge corn crop this year and being shut out of some export markets has driven US corn prices to record lows which will trigger US government subsidies to GMO farmers of up to $8 bil USD for this year.