The difference is that oil is a money maker for Russia, grains and fertilizer are not so much (and are likely subsidized as part of an effort to exert influence

The difference is that oil is a money maker for Russia, grains and fertilizer are not so much (and are likely subsidized as part of an effort to exert influence). Russia has little problem withholding food resources as a way of forcing cooperation. If the US can actually get Russia to agree to play their best card in exchange for almost nothing, it could be an overall win.