Alfalfa hay production removes large amounts of phosphorus (P) and potassium (K) from soils. Because of this, there is always interest in the reduction of soil test phosphorus (STP) and soil test potassium (STK) levels by high-yielding alfalfa. Periodic soil sampling for 2 years during an on-farm· fertilizer study on a high yielding alfalfa field provided an insight into this.
Wells, Kenneth L. and Dollarhide, James E., "Drawdown of Soil Test Phosphorus and Potassium levels by Alfalfa" (2000). Soil Science News and Views. 131.