Why does China spend so much on agricultural/farming subsidies? I use the OECD's Total Support Estimates (TSE), which I think is a proper measure of total agricultural subsidies (but correct me if I'm wrong). 

China's TSE is by far the largest at \$239B in 2017 and even its per-capita TSE (PPP*) is higher than the US's.



Here are some explanations I have come across for why agriculture is heavily subsidized in the rich democracies:


Rural voters wield disproportionate power.
The costs (of the subsidies) are diffuse and so no single voter has much incentive to organize/lobby against the subsidies.
Voter inattention: The voters who pay for the subsidies are simply unaware that they are doing so.


However, China is not a democracy and so it would seem that the above explanations do not apply. So what explains China's large agricultural subsidies? 



*I think (but am not sure) the TSEs given by the OECD have not been corrected for PPP. And so, I have taken the liberty of converting them.

Google spreadsheet with data and sources.
The first thing that comes to mind is food security. China has a large population to feed and does not want to depend on foreign nations for its food. 

A (speculative)  second reason may be prevention of domestic unrest. The largest share of China's population still lives in rural areas, and by supporting farmers they may silence protests. 

A recent article analysing the drivers of China's agricultural policies by Lopez et al., including the fairly recent shift from taxes to subsidies can be found here: 
https://www.sciencedirect.com/science/article/pii/S0305750X1630211X