I would take a soil sample for $13. You may even have a low PH that you were not aware of because of the two crops you had, Rye and Oats, do grow in acidic soils. In addition, as Jack mentioned, I would go with an annual clover versus a perennial clover if your going to disk the field each year. Again, take a soil sample as it is cheap and can save you $$ and aggravation. You might have already, but if not, try to get your PH in 6.5 range. Soil sample also tells you how much fertilizer you need. Without the soil sample, the 13-13-13 sounded fine. I'm really picky with my plots and PH's, but others may not be. If you like great plots, get PH at a good range. Good luck.