the higher the skill the better chance of getting a higher yield at harvest(all levels were tested on cotton fields so it may differ on other crops)
* at 20 skill you will get a guaranteed 3
* at 35 23 skill you will get a chance at 4(12/28/12 on pristine (cotton))
* at 40 skill you will get a guaranteed 4 (42 for wemp)
* at 60 skill you will get a guaranteed 6