Irrigated corn yield and soil phosphorus response to long‐term phosphorus fertilization

Long‐term experiments can help to understand soil phosphorus (P) dynamics and improve nutrient management strategies. This research evaluated long‐term (2002–2021) soil P dynamics and yield response to a range of P fertilizer rates in a continuous high‐yielding irrigated corn ( Zea mays L.) experiment with low initial soil phosphorus test (SPT, 10.5 mg kg −1 ). The experiment was established near Clay Center, NE, and five P rates (0, 10, 20, 39, and 59 kg P ha −1 ) were evaluated. Soil samples at 20‐cm depth were collected in eight cropping seasons. Yield response to P fertilizer increased after 20 years from 0.64 to 2.79 Mg ha −1 . The application of 39 kg P ha −1 year −1 increased soil Bray‐1 P to 19.5 mg kg −1 , outyielded all other P treatments, and resulted in a positive relative P balance. Over 20 years, 0 kg P ha −1 year −1 decreased Bray‐1 P from 10.5 to 5.5 mg kg −1 . Annual P rates of 0, 10, and 20 kg P ha −1 produced a negative relative P balance and SPT below the critical soil test value (CSTV). The CSTV was 22.2 mg kg −1 for a continuous irrigated corn cropping system. A 53% increase in the P fertilizer rate (from 39 to 59 kg P ha −1 year −1 ) produced a threefold increment in the soil test P build‐up rate. High‐yielding irrigated continuous corn production systems (>14 Mg ha −1 ) are required to apply at least 39 kg P ha −1 year −1 to maintain SPT and a positive relative P balance over years.