INFLUENCE OF PHOSPHORUS AND NITROGEN ON ANNUAL BLUEGRASS ENCROACHMENT IN A CREEPING BENTGRASS PUTTING GREEN

摘要

Annual bluegrass (Poa annua L.) encroachment into newly established creeping bentgrass (Agrostis stolonifera L.) putting greens is a concern for golf course turfgrass managers attempting to maintain uniform and consistent putting surfaces.A 2-yr field study was conducted at the Joseph Valentine Turfgrass Research Center (University Park,PA USA) on a 2-yr-old sand-based ‘Penn A-4’ creeping bentgrass putting green to determine the influence of phosphorus (P) on changes in annual bluegrass cover and to identify soil and tissue P concentrations associated with limited annual bluegrass encroachment.Treatments were the factorial combination of four nitrogen (N) rates (195,293,391,and 488 kg N ha-1) and four P rates (0,43,86,and 129 kg P ha-1 yr-1).Treatments ≥ 43 kg P ha-1 yr-1 resulted in an increase in annual bluegrass cover compared to treatments with no P applied,but annual bluegrass cover was not affected as rates of P increased above 43 kg P ha-1 yr-1.Annual bluegrass cover in 0 kg P ha-1 yr-1 plots decreased by 2% over the 2-yr experiment; whereas,cover increased from ~3 to 7 % in plots receiving 43 to 129 kg P ha-1 yr-1.After 2-yr of treatments,soil Mehlich 3-P concentrations were positively correlated with changes in annual bluegrass cover; treatments producing concentrations >13 mg kg-1 had greater annual bluegrass cover than those measuring < 13 mg kg-1.Tissue P concentrations were significantly correlated with changes in annual bluegrass cover on all evaluation dates during this 2-yr study.Treatments producing tissue P concentrations ranging from 4.0 to 5.5 g P kg-1 had less annual bluegrass cover than treatments producing tissue concentrations > 5.5 g P kg-1.Nitrogen had no effect on annual bluegrass encroachment and no N-by-P treatment interaction occurred during the study.