Response to Phosphorus and Potassium Fertilization for Corn and Soybean Grown in Rotation in a long term experiment

PABLO A. BARBIERI; ANTONIO P. MALLARINO

Long Beach, California

Congreso; ASA, CSSA & SSSA International Annual Meetings; 2014

ASA, CSSA & SSSA

Corn and soybean crops are commonly fertilized with P and K and represent a significant cost to producers. Therefore more efficient fertilizer management strategies are necessary. The objective of this study was evaluated yields of both crops as well as changes in soil test values when P and K fertilizers were applied at various rates. Treatments were the factorial combinations of P (0, 22, and 44 kg P ha-1) and K (0, 67, and 134 kg K ha-1) annual rate on a long-term experiment, initiated in 1979 to an initially high-testing soil. The P and K treatments have affected soil-test values significantly. Soil-test P from the control plots decreased to 9.9 ppm from initial 28 ppm, and soil-test K in control plots decreased to 96 ppm from initial 170 ppm. While plots receiving P and K fertilization increased soil-test over time. These increments were from 45 to 120 ppm for 22 and 44 kg P ha-1, respectively, and from 190 to 393 ppm for 67 and 134 kg K ha-1. No significant interaction P x K on grain yield was determined. Grain yields of corn and soybean were significantly affected by either P or K fertilization. In general there were no large or consistent differences between the P and K rates. However, about 17 years after experiment began there were very small or no yield increases from P and K fertilization. Decreasing soil test-values of non-fertilized plots into the Low P and K soil-test interpretation classes explained yield response to fertilization for either crops. Gain yield from treatment that received both P and K yielded more than treatments that received either P or K alone. In conclusion, these results showed that producers can increase crop profitability production by using soil testing and applying P and K in low-testing soils.