The Trump tariffs aren't the main reason for falling grain, specifically soybean, prices.
The USA has millions upon millions of tons of carryover stocks from the past few years, and this year's crop of soybeans and corn looks like a bin-buster unless we get some horrible harvest weather. As such, there will be even more excess crop around and prices aren't going to rebound until those excess stocks are used up. Couple of years at least.
Chinese tariffs have almost nothing to do with it. If the Chinese buy beans from elsewhere, then those who would have bought those beans will buy ours instead. Six of one, half dozen of another.
Any good soybean farmer contracted at least half his expected harvest already at the good prices available this spring, so they will be in okay shape. Those who don't bother contracting ahead, or are greedy and wanted to get even more, will be hurting this fall. Next spring is going to be a tough call on grain farmers, as barring a major harvest catastrophe somewhere in the world over the winter, the excess stocks aren't going to be eaten-up by anyone by next spring. Low prices should be expected.
Farmers in the USA mostly, and the good ones elsewhere in the world, are simply too good at what they do (producing lots of food). They can never create a true scarcity of supply.
