A long term evaluation of differential potassium fertilization of a creeping bentgrass putting green

Abstract

Aims: The objective of this research was to evaluate bentgrass quality, growth, and disease incidence over a range of soil and tissue potassium levels. Methods: ‘Penn A4’ creeping bentgrass (Agrostis stolonifera L.) on a sand root zone was maintained as a putting green. The treatments included four levels of liquid potassium sulfate, ranging from 0 to 249 kg ha−1 yr.−1 K and one level of granular gypsum at a rate of 100 kg ha−1 yr.−1 Ca. Results: No differences in vegetative or quality parameters were observed over the 6 year study period. Tissue K, Mehlich-3 extractable K, and Microdochium patch infection were all affected by treatment, with high-K treatments being greater than control and Ca treatments in all three instances. Near-daily turfgrass harvest resulted in much greater K removal than was estimated to be available from the pools extracted by Mehlich-3 and 1 M HNO3, suggesting that K became plant-available from more recalcitrant pool. Conclusion: Traditional soil testing methods may be inadequate for determining plant-available K in sand root zones. Total soil K analysis of the 0-K treatment indicated an increase in K during the study period, likely as a result of regular additions of sand via topdressing. Weathering of mineral K likely provided sufficient K to compensate for the lack of fertilizer.