I'm Using Mapshot's AgStudio. I write seeding, fertilizer, and lime prescriptions with it based on yield data, soil tests, crop removal, etc. My subscription with the options I have runs about $1300/year. But if you just want to use the agronomy side of it, it's quite a bit cheaper. I looked at SMS but i didn't like the layout and it didn't deal with the business part of the farm real well