I don't know what the first few lines of your reply are supposed to mean.

Using less fertilizer because of low prices makes perfect economic sense.  The marginal return is different under different price structures.  Planting different crops because of different price relationships also makes perfect economic sense.  Refusing to plant anything only makes sense if the variable costs of planting are greater then the expected return.  As long as production exceeds variable costs, then the decision to produce is clear cut.

Economics is mathematics. There is a better and worse answer to each question.  Your fuzzy logic does not apply to mathematics.