What you're doing looks good, but I'm not farming so take that for what it's worth!

Before you sell any copies, take a long, hard look at yourself and decide whether you want to make the transition to supporting and developing for someone else. I deal in the spreadsheet world and only develop for myself, my boss, and our sales crew. If it takes one hour to do something for me, it will take 2 hours to do it to the level needed by my boss, and 10 hours to be good enough to support the salespeople. A big part of developing for others is understanding what they really want.

If I run into a problem using my own spreadsheet, it's not a big deal. I see the problem and can easily fix it on my own schedule. If a salesman has a problem, I need to spend additional time troubleshooting it, and fixing it, then verifying I didn't break something, then making sure I can get the latest copy rolled out to everyone. Do that a couple times in one day, and people will start wondering about your application.

Even bigger than support would be deciding what to work on. It won't take long before someone asks for a feature that sounds good but won't work unless you redesign the program. "4 crops? But I need five. Can you do that for me?" After upping this to seven crops, you finally decide to make this a relational table thing with unlimited crops. Oh crap, now the printed page formats don't work anymore. Or, "my business name ('Father and Son Farming Illinois, Indiana and Every Other State Starting with "I"') won't fit in the title section." Or, "I want to be able to download the records to my iPhone and update them there. Can you do that?"

I'm not trying to discourage you. I'm just suggesting you take a look and decide if you have the patience to deal with the needs and limitations of others using your program. If you're able to do that, you've got a great head start!

What you have developed looks like a neat program.  I agree with what Omar said on the business side of things.  My previous experience dealing with gis software support is it is very hard for people to grasp things over the phone especially when they have limited experience with the program.  Obviously there are programs that allow someone to take over another users computer but then the end user doesn't learn anything on how to think through the problem on their own when the next issue arises.  Unfortunately sometimes it is easier to keep things that you develop to yourself unless there are the necessary resources to have your sideline business.  Its really cool that you developed that program on your own.