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Interpretive Summaries:
2003 - Potassium Needs of High-yielding Alfalfa in Colorado
2002 - Potassium Needs of High-yielding Alfalfa on the West Slope of Colorado
2001 - Potassium Needs of High-Yielding Alfalfa on the West Slope of Colorado
2000 - Potassium Needs of High-Yielding Alfalfa on the West Slope of Colorado
Potassium Needs of High-Yielding Alfalfa in Colorado, 2003
Most of the soils in crop production in Colorado test high in potassium (K). In fact, a 2001 PPI soil test survey estimated that only 10% of soils in Colorado test medium or lower in K. Therefore, K fertilizer is seldom recommended by the state soil testing laboratory. In spite of this, some producers and ag professionals have reported profitable response to K application to alfalfa. The objective of this project is to evaluate the impact of K fertilizer on alfalfa yields in on-farm trials in different locations across Colorado.
Application of K to three study sites in Colorado was continued in 2003. The sites were located in central Colorado (San Luis Valley), northeastern Colorado (Eaton), and another in the Arkansas River Basin (Rocky Ford). Irrigation problems arose at the Eaton site. Consequently, 2003 yield data at this site were not obtained. All sites tested high in K, hence no K fertilizer would have been recommended for these fields. Potassium fertilizer was applied to each site in the fall of 2002. Treatments included rates of 0, 40, 80, and 180 lb K2O/A.
As in the 2002 season, no response to K fertilizer was observed at either location in 2003. Alfalfa showed significant response to K fertilizer on previous sites (1999 and 2000) in this study on the western slope of the Colorado Rocky Mountains. No response has been observed in central or eastern Colorado. This inconsistency is likely due to differences in soil chemistry and/or mineralogy. This was the final year of funding for the study. CO-10F
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