The most obvious data sources cover the basics. Oryza lists rice price quotes for multiple qualities and grain types, useful for importers and exporters who traffic in specific lines and must account for logistics. NASDAQ's quote only lists one price for CBOT rough rice, which is probably sufficient for US-based producers but insufficient for analysts tracking global rice production. The UN's FAO reports regular prices for multiple foodstuffs, including the world rice price. IFPRI's Food Security Portal defines the world rice price as "the monthly average of weekly prices for White Broken Rice, Thai A1 Super, and FOB Bangkok." Now we're getting to a broad, singular metric. Aggregate market data is available in the FAO Rice Market Monitor (RMM), FAO Rice Price Update, and USDA Farm Service Agency "Rice Reports" (check the website's Food Grains Analysis section).
A quick perusal of Google search results related to rice farming reveals the ability to flood a field as a crucial input. Cold weather can prevent timely flooding. No farmer wants a frozen rice paddy. I don't recall seeing any rice fields whenever I visited Wisconsin, but that cold state does have plenty of cranberry bogs. I expect California's continuing drought to seriously harm water-intensive crops like rice. The microeconomics of farm management is beyond the scope of my blog.
There is no pure-play tradeable security covering only the rice subsector of agribusiness. Commodity ETFs and agribusiness sector ETFs have only limited rice exposure. Adventurous rice investors may look to CME Group's Rough Rice Futures for contract exposure. Rough rice futures can be a hedge for farmers, traders and others who are directly exposed to US rice production and NASDAQ's price quote, but these futures do not necessarily correspond to FAO's world rice price. Arbitrage is only possible when the same commodity has a different price in two markets. The US rice price and the world rice price are not the same thing, just as the WTI oil price is not the Brent price. Perhaps the rice price spread between the US and the world can tell us as much about production and distribution costs as the WTI-Brent crude spread.
I have noted that other commercial data services exist to track the rice business, but they mostly repeat the free data anyone can get from the USDA and FAO. The analyst community needs more than price knowledge to track the rice ROI. Weather, logistics, soil quality, and regulation all matter. Energy utilization also matters; fertilizer needs ammonia and natural gas, and pesticides need petroleum. The very divergent prices for rice make farming a challenge. I am glad to be an analyst, and not a rice farmer.
Full disclosure: No exposure to rice-related financial instruments at this time. The author does frequently eat rice, and has a few bags of the stuff at home.