Effect of Long-term Nitrogen, Phosphorus and Potassium Fertilization of Irrigated Corn and Grain Sorghum
IPNI-1991-USA-KS23
26 Jan 2010
2009 Annual Interpretive Summary
This long-term western Kansas study was initiated in 1961 to evaluate responses of irrigated continuous corn and grain sorghum to N, P, and K fertilization. Furrow irrigation was used through 2000, and sprinkler irrigation since 2001. No yield benefit to corn from K fertilization was observed in the first 30 years and soil K levels remained high, thus the K treatment in the corn study was discontinued in 1992 and replaced with a higher P rate. Nitrogen treatments for corn and grain sorghum were 0, 40, 80, 120, 160, and 200 lb N/A. Phosphorus treatments for corn and grain sorghum were 0, 40, and 80 lb P2O5/A, and 0 and 40 lb P2O5/A, respectively. The K treatments for grain sorghum were 0 and 40 lb K2O/A.
The 2009 results of this project continue to demonstrate that fertilizer inputs are important to the production of irrigated corn and grain sorghum in western Kansas. Corn yield in the no fertilizer control was 85 bu/A in 2009. Nitrogen alone increased corn yield by as much as 70 bu/A, while co-application of N and P increased yield by over 150 bu/A. Averaged across the past 9 years, co-application of N and P increased irrigated corn yield by 139 bu/A. Application of 120 lb N/A (with P) was sufficient to produce >90% of maximum yield in 2009, which was similar to the 9-year average. Phosphorus fertilizer at the lowest P rate increased corn yield by over 85 bu/A with 120 lb N/A, and application of the highest P rate increased yield by an additional 13 bu/A. The no fertilizer treatment in the sorghum study produced 64 bu/A. Nitrogen fertilizer alone increased sorghum yield by as much as 51 bu/A, while N plus P increased yield by 75 bu/A. Application of 40 lb N/A (with P) was sufficient to produce about 85% of maximum yield in 2009, although yields continued to increase with higher N rates. Potassium fertilization had no effect on sorghum yield over the course of the study. This is one of the few continuous, long-term crop nutrition studies in the U.S. and support is planned to continue in 2010. KS-23F