Effect of biological additives to a putting green with low plant‐available phosphorus

Abstract The use of phosphorus fertilizers on managed turf has become discouraged, if not restricted, in many places because of the risk of pollution of surface waters posed by excessive phosphorus application. Therefore, nontraditional options to increase phosphorus availability to turf are worthy of investigation. The objectives of this study were to evaluate the effect of additions of arbuscular mycorrhizal fungi and an N‐fixing bacterium, Methylobacterium symbioticum , on the nutritional status of a mature bentgrass putting green on a sand root zone with low plant‐available phosphorus status. The biological amendments were added at various intervals after aerification, and turfgrass responses were recorded over two field seasons. Mycorrhizae did not result in increased turfgrass visual quality, clipping yield, or clipping P content. Additions of the N‐fixing bacterium resulted in increased mid‐season clipping N content and increased visual turfgrass quality, but the overall effect was relatively small. It appears that applications of M. symbioticum to turfgrass hold promise for improving nutrient use efficiency and visual turfgrass quality and deserve future exploration.