
Clarke Co, Iowa  You are not giving nearly enough information to answer your question. First how much actual P and K are you putting on per acre? Next what does a gallon of that liquid fertilizer weigh? (I think in the area of 13 pounds per gallon.) Given that each gallon has about 2and 1/3 pounds of P and K each. 50bushel beans use up 42 pounds of P and 65 pounds of K. So, it only takes about 27 gallons of 31818 to put on 65 pounds of K. Anything less and you're mining the soil.  
