Cycling of composted biosolids through turfgrass sod enhances sustainability across agricultural and urban landscapes

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Commodities

• Additional Plants: ornamentals

Practices

• Crop Production: municipal wastes, nutrient cycling
• Farm Business Management: agricultural finance
• Sustainable Communities: community development, urban/rural integration

Municipal programs promoting composted municipal biosolids (CMB) as soil amendments for turfgrass establishment recommend large volume-based application rates. Turfgrass establishment practices were compared to evaluate impacts of volume-based rates of contrasting CMB sources on runoff water quality. Sod transplanted from Tifway bermudagrass [Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt-Davy, var. Tifway] turf topdressed with a 1.2-cm depth of two CMB sources was compared to Tifway sprigged in soil mixed with 12.5% and 25% by volume of each CMB during eight natural rain events. The two CMB comprised High (9500 mg P/kg) and Low (5800 mg P/kg) concentrations of total P. Sod grown with High-P and Low-P CMB, sprigged plots amended with the two rates of High-P and Low-P CMB, and an established bermudagrass control made up seven treatments that were replicated three times on an 8.5% slope. Runoff was sampled after each of eight natural rain events and soil was sampled to a 5-cm depth after the eighth event. Topdressing or incorporation of a 1.2-cm depth of CMB supplied 280 kg/ha of total P from Low-P CMB and 599 kg/ha of total P from High-P CMB. Although import of CMB in transplanted sod limited sediment loss, sod transplanted from turf top-dressed with the 1.2-cm depth of High-P CMB contributed to greater soil and runoff concentrations and mass loss of total N and P than the same depth incorporated to a 5-cm soil depth before sprigging. Incorporation of CMB in soil minimized differences in mass loss of total N and P in solution and sediment among volume-based CMB rates applied to sprigged treatments and the control. Regression analysis indicated concentrations of extractable P in soil amended with CMB were directly and positively related to concentration and mass loss of dissolved P in runoff.

Introduction

Many municipalities and associated industries produce and market composted municipal biosolids (CMBs) as soil amendments for vegetation establishment, including turfgrass, on commercial and residential landscapes (City of Austin, 2001; Dickerson, 1999; Milwaukee Municipal Sewerage District, 2004). Recycling CMB across urban landscapes diverts waste streams from landfills and facilitates nutrient and carbon cycling. Historically, the use of CMB in turfgrass management systems focused on plant responses to amended soils (Schlossberg and Miller, 2004; Loschinkohl and Boehm, 2001; O’Brien and Barker, 1995; Flanagan et al., 1993). The CMB amendments decreased incidence of disease, enhanced color, reduced establishment time, and delayed water stress of turfgrass established on disturbed urban soils and sod production fields (Boulter et al., 2002; Loschinkohl and Boehm, 2001; Garling and Boehm, 2001; Smith, 1996; Murray et al., 1980).
Depth- and volume-based CMB application rates are promoted through municipal programs. For example, the City of Austin, Texas recommends incorporation of 25% by volume of CMB into a 15-cm depth of soil or topdressing of a 0.6-cm depth of CMB (City of Austin, 2001). Similarly, evaluations of CMB amendments for turfgrass have included large, volume-based CMB rates to enhance soil physical properties during establishment on poor quality soils (Landschoot, 1995; Cisar, 1994, Angle, 1994). Yet, little information concerning nutrient losses in surface runoff from soils amended with the large volume-based CMB rates is available.
Line et al. (2002) identified compost and mulches among factors that contributed to nutrient loss in runoff water from urban construction sites. Nutrient losses in runoff water from amended soil and turf are expected to increase as nutrient concentrations in soil increase, whether applied as inorganic or organic fertilizer sources (Easton and Petrovic, 2004; Vietor et al., 2004; Gaudreau et al., 2002). The nutrient loads in urban runoff are considered a major source of non-point surface water pollution (Carpenter et al., 1998).
Large, volume-based applications of CMB to soil need to be evaluated to quantify nonpoint-source nutrient losses in surface runoff from urban landscapes. In addition, the traditional approach of mixing CMB with urban soils prior to sprigging or seeding of turfgrass needs to be compared to the practice of importing CMB in sod transplanted for turfgrass fields grown with CMB (Vietor et al., 2004). A previous study indicated transplanted sod delayed runoff of simulated rain more than wood or fiber blankets applied to 8% or larger slopes on simulated construction sites (Krenitsky et al., 1998). A comparison of runoff losses from CMB-amended soil and CMB-amended sod will contribute to optimal practices for minimizing sediment and nutrient losses during vegetation establishment and soil stabilization at urban construction sites.

The objectives of this study were: (i) quantify and compare export of total and extractable P and N in sod harvests among turfgrass sources produced with inorganic fertilizer and two sources and rates of composted municipal biosolids (CMB), (ii) quantify and compare P and N runoff losses between sod transplanted from CMB-produced turfgrass and turfgrass sprigged in CMB amended soil, and (iii) relate runoff concentrations and mass losses of P to extractable soil P concentrations of turf establishment treatments.