Effect of potassium application rate and timing on alfalfa yield and potassium concentration and removal in Tennessee
¹University of Tennessee, Department of Plant Sciences, West Tennessee Research and Education Centre, 605 Airways Blvd., Jackson, TN 38301-320, USA
²University of Tennessee, Department of Biosystems Engineering and Soil Science, 2506 E J. Chapman Dr, Knoxville, TN 37996, USA
³University of Tennessee, Department of Biosystems Engineering and Soil Science, West Tennessee Research and Education Centre, 605 Airways Blvd., Jackson, TN 38301-320, USA
Alfalfa (Medicago sativa L.) is the most important forage crop in the world and potassium plays a significant role in achieving high yields. A field experiment was conducted during the 2012–2014 growing seasons at the University of Tennessee in Springfield. The experimental design was a split-split plot that included four levels of potassium (K) application rates (0, 67.25, 134.50, and 269.00 kg K2O ha-1) as the main plots and two K application times (green-up and split) as the subplots, and harvest dates as sub-subplots. The results demonstrated that the dry matter yield (DM) increased significantly with each increment in K application rate up to 134.50 kg K2O ha-1; however, the highest K fertilizer application (269 kg K2O ha-1) did not result in a significant yield increase relative to 134.50 kg K2O ha-1, because some luxury consumption of K occurred at the highest rate due to yield leveling off while K2O uptake continued to rise. Potassium concentration and K removal increased with K fertilizer at rates beyond those that maximized yield, indicating luxury consumption of K. The greatest K concentration and removal were recorded at 269 kg K2O ha-1 in all harvest months. The split application was more beneficial than applying full K at the time of green-up due to higher dry matter, K concentration, and K removal in alfalfa. In conclusion, 134.50 kg K2O ha-1 is adequate for maximizing alfalfa yield; split application of K is sometimes superior to the single dose of K fertilizer in alfalfa production.