Crops on barren soil should only give 1-2 produce. On low fertility soil 2-3. On medium fertility soil 3-4. On compost 4-5 and on terra preta 5-7 or 5-8.
It should also be visible when the plant is growing. For example if the plant will only give 3 produce we will only see 3 plants on that block.
And it would also look nice if the size of the crop is different dependent on how many crops grow on that block. For example barren soil will only have tiny plants
wich arent super green looking. On medium soil they are normal sized and colored. But on terra preta they are huge and super green and good looking.
It would also look cool if the crops are rotated on the field so it makes for more diverse looking field.