Potassium Leaching As Affected by K Source.

Leaching of potassium (K) in sand-based putting greens is possible, and use of slow-release K fertilizers may help slow this downward movement of K.  The objective of this project was to evaluate K leaching as affected by K source.  Conducted in the greenhouse, the study consisted of 2 repetitions of the following K treatments, with 5 replications of each:  1) potassium chloride, 2) potassium sulfate, 3) resin-coated potassium sulfate, 4) an experimental methylene urea containing K, and, 5) an unfertilized control.  In each experiment 6.4 cm diam. cores of 'Penn G-2' creeping bentgrass (Agrostis stolonifera L.) were removed from a 3 yr old putting green and moved to the greenhouse, where roots were trimmed and each core placed in a 30 cm long cylinder filled with sand.  After 3 wk of fertilization via a 0 K Hoaglands solution the K treatments were applied.  Potassium was applied at 168 kg ha^-1, following soil-test recommendations.  Each week for 10 weeks cores were leached, and resultant leachate collected and analyzed for K.  Additional data included clipping yield, clipping K content, root mass at experiment end, and final K content in soil.  At the end of 10 weeks a portion of the resin-coated K was still in the fertilizer prill, and had not yet been released into the soil.  There were significant differences in K leaching and uptake due to K source, with significantly more K leached from cores fertilized with potassium chloride and potassium sulfate than from the resin-coated K source.