Problem with Plantation Management: Tending Fields

I've seen no one mention this issue, so I'm going to assume I'm making a silly mistake:
I've recent acquired plantation management. With an iron hoe, I tended a few fields and noted that the upkeep did not reduce whatsoever and remained at 50%. I made certain that the tending action had completed on these fields and verified that the "tend" option no longer appeared when I clicked on them. These fields were in stage 1 of cotton. Uncertain if it makes a difference, but I had planted the crops before acquiring plantation management. I harvested one of the fields to see if it would magically reduce afterward, but this did not happen. If anyone has some guidance, I'd greatly appreciate it. Thanks!
I've recent acquired plantation management. With an iron hoe, I tended a few fields and noted that the upkeep did not reduce whatsoever and remained at 50%. I made certain that the tending action had completed on these fields and verified that the "tend" option no longer appeared when I clicked on them. These fields were in stage 1 of cotton. Uncertain if it makes a difference, but I had planted the crops before acquiring plantation management. I harvested one of the fields to see if it would magically reduce afterward, but this did not happen. If anyone has some guidance, I'd greatly appreciate it. Thanks!