Phosphorus response and loss from cool-season turfgrass following initial establishment

Jared R Nemitz, Purdue University

Abstract

Both public and regulatory communities perceive turfgrass (e.g. lawns) to be a significant contributor to declining water quality. The primary regulatory concerns are sediment and nutrient loss, particularly phosphorus (P). Excess P in surface water results in eutrophication, a biological process by which increased phytoplankton growth may reduce water quality through fish kills and algae blooms, habitat loss and decreased dissolved oxygen levels. Therefore, understanding the extent of sediment and P loss as well as quantifying the effect of P rates during cool season establishment is important. Two greenhouse studies were conducted on a Stark (Aeric Ochraqualfs) clay-loam, calcareous sub-soil with an inherent soil P-level of 12 and 4 mg P kg-1 for the Olsen and Bray P-1 soil test, respectively, to quantify the effects of seven P-rates on seedling establishment and growth for two commonly cool-season lawn species; tall fescue [Schedonorus phoenix (Scop.) Holub; formerly known as Festuca arundinacea Schreb.; TF)] and Kentucky bluegrass (Poa pratensis L.; KBG). Additionally, the influence of TF endophyte (E) stem infection (TFE+) on establishment and rooting was assessed. In the first greenhouse study, lasting 11 wks, seven soil P-rates (0, 3, 9, 15, 25, 45 and 75 mg P kg-1) were applied to a clay loam sub-soil. Tall fescue was much quicker to establish reaching 50% turf cover 14 d quicker than KBG. Even at a rather low endophyte stem infection rate (24%), TFE+ had superior turf coverage on six of nine rating dates compared to TF without E (TFE-) during the first 8 wks of establishment. The addition of 45-75 mg P kg-1 (98-161 kg P2O 5 ha-1) to the surface soil surface optimized establishment for both species in this study. Leaf tissue P concentrations (LTP) were generally low or critical (1.6-3.8 g kg-1) for P rates ranging between 3-25 mg P kg-1 for KBG. Tall fescue produced more total dry matter yield (DMY) than KBG, while TFE+ (2,157 kg ha-1) produced more DMY than TFE- (1,745 kg ha-1). In a follow-up greenhouse study, root dry weight for TFE+ was 2.28 g pot-1 compared to TFE- that only had 2.08 g pot-1. This may partially explain why TFE+ outperformed TFE- throughout our study, perhaps contributing to greater soil nutrient acquisition. Two rainfall simulation events were conducted 14 and 42 days after planting (DAP) with a moderate intensity rainfall, ≈ 40 mm hr-1. The two simulated rainfall events quantified the potential sediment, liquid runoff volume and P losses from several common and novel cool-season turfgrass establishment methods. Turfgrass coverage ranged from 0-100% and influenced runoff and sediment losses. Bare soil resulted in sediment losses of 339 and 91 g m-2 at 14 and 42 DAP compared to sod that only lost 14 and 11 g m-2 14 and 42 DAP, respectively. During the first rainfall simulation 14 DAP, all establishment methods resulted in 57 to 81% reductions in total cumulative runoff loss compared to bare soil. The use of sod, sod buffer strips and straw blankets were highly effective in reducing sediment (13-57 g soil m-2) and runoff losses (3.6-10.4 mm water) compared to seeded treatments (78 g soil m-2) and bare soil (339 g soil m-2). The highest cumulative mass soluble P (SP) loss in runoff, however, were from sod, sod buffer strips, straw blankets and seed + low P (32 kg ha-1) treatments with concentrations ranging from 42-127 mg P for the rainfall simulation 14 DAP. However, the sod, sod buffer strip and straw blankets had the lowest cumulative total P loss due to low sediment loss from those treatments. These studies demonstrate that to minimize sediment and nutrient loss from newly seeded turfgrass ecosystems a species that establishes rapidly, such as TFE+, should be planted and adequate P-rates will speed seedling development with minimal risk of nutrient and sediment loss. Furthermore, erosion control fabrics or small sod buffer strips may help minimize runoff losses during establishment.

Degree

M.S.

Advisors

Beyrouty, Purdue University.

Subject Area

Agronomy|Soil sciences

COinS