Potassium fertilizer influences on coastal bermudagrass yield and nutrient uptake and on available soil potassium levels

Abstract

Coastal bermudagrass yields were increased by 3.1 Mg ha^‐1 with K applications of 300 kg ha^‐1 yr^‐1 in a 7‐year study on Olivier silt loam at Baton Rouge, but available soil K depletion occurred even though K applications exceeded K removal in the forage. At lower rates of K application, K removal exceeded K applications, causing severe depletion of available soil K. Applying 600 kg of K ha^‐1 exceeded both the crop K requirement and K removal in the forage, resulting in increased levels of available soil K. Ninety percent of the maximum yield was obtained at about 100 kg of K ha^‐1. Potassium concentrations in the forage averaged 9.2 and 13.4 g kg^‐1 at K rates of 100 and 300 kg ha^‐1, respectively. Apparent recovery of fertilizer K decreased from 53 to 47% as K applications increased from 37 to 300 kg ha^‐1. The Olivier silt loam supplied 105 kg of K ha^‐1 annually where no K was applied. The study indicates that K applications must be sufficient to produce yields very near the maximum yield in order to avoid depletion of available soil K by high‐yielding Coastal bermudagrass.