Potassium Fertility in 2010

Shifting crop rotations and nutrient removal rates, along with unprecedented fertilizer prices have resulted in a deficit in potassium levels in many fields in the state.  The road to this deficit is understandable; high fertilizer prices did not fit into the bottom line the past two years.  Soybeans and wheat have traditionally not been high input crops and good yields in these crops have lowered field reserves.  Going into next year, it will be very important to recognize that good yields in all crops require adequate potassium fertility.  Crops differ in the amount of potassium utilized during the growing season and in the amount that is removed with harvest.  Cotton and soybeans provide a good example.  Cotton is traditionally known as a crop that requires high potassium fertility levels.  According to the Potash & Phosphate Institute, a cotton crop yielding 750 lbs./acre and a soybean crop yielding 30 bushels/acre both utilize 105 lbs./acre of K₂O during the growing season.  With cotton harvest, 30 lbs./acre of K₂O is removed; with soybean harvest, 42 lbs. K₂O is removed.  While both crops need good potassium levels for growth and development, soybeans actually remove more per acre in relation to crop uptake.