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.