By the time you have this information and are reasonably act on it, it has already been priced in by participants with deeper pockets, better access, and rapid processing of relevant information sources.
Also, the situation is very dynamic with an unknown and very large number of variables, even with something as seemingly simple as a crop failure. Such as such as a countries deciding to ban exports to secure food security, lack of access to fertilizer due to sanctions against major fertilizer producers in wheat producing countries, the politics of national and local water rights.
All these factors have parties with inside information acting on them (see members of congress trading stocks) which no player with big pockets will have access to but is all reflected in the price.