The outbreak and continuation of the COVID-19 pandemic have affected the trade policies of various countries and influenced global food security. This paper aims to use U.S. major grain commodity futures price and trade policy uncertainty (TPU) index data to examine the impact of TPU on the volatility of U.S. grain futures prices under the GARCH-MIDAS framework. The in-sample estimates confirm the impact of TPU on the volatility of US grain commodity futures prices. Out-of-sample testing further reveals that considering TPU could improve predictions of future price fluctuations for different grain commodities. Finally, we also consider other uncertainty indices. Since the grain market is often used as a tool to hedge financial risks, this article can provide some advice for investors in times of policy instability and especially trade policy uncertainty.

COVID-19大流行的爆发和持续影响了各国的贸易政策，影响了全球粮食安全。本文旨在利用美国主要粮食商品期货价格和贸易政策不确定性（TPU）指数数据，在GARCH-MIDAS框架下考察TPU对美国粮食期货价格波动的影响。样本内估计证实了 TPU 对美国粮食商品期货价格波动的影响。样本外测试进一步表明，考虑 TPU 可以改善对不同谷物商品未来价格波动的预测。最后，我们还考虑了其​​他不确定性指标。由于粮食市场经常被用作对冲金融风险的工具，