4-6-30 is what I put on mine. Avoid putting much nitrogen(assuming they were innoculated or you had beans on it in the last few years), it will only slow the formation of the nitrogen fixing nodules that will provide most of the 300 units/acre of nitrogen required for a decent crop. You might need more phoshorus than I did, soil test shows plenty for me. Soybeans need a good amount of potash to make a decent crop. I put 80 units/acre on mine, and probably could have used more. A decent soybean crop will use 50-60 units of potash.