Beneficial Reuse of Biosolids for Kentucky Bluegrass Sod Production

Linking sod production to waste management via land application of municipal biosolids can lead to beneficial disposal of nutrient rich waste. Biosolids may also mitigate the loss of soil from sod fields during harvest operations. The objective of this study is to increase the profitability and sustainability of sod production by developing a biosolids-based sod production system in Wisconsin. Four replications of seven treatments were arranged in a randomized complete block design at a sod production farm in Marshall, WI on a Dodge silt loam (Fine-silty, mixed, superactive, mesic Typic Hapludalfs). Plot size was 25 m by 8 m, and all operations were performed using farm equipment. Two biosolids materials were utilized from the Madison Metropolitan Sewage District (dewatered class B biosolids cake and cake mixed with sand and sawdust), and were applied at three rates based on their estimated supply of plant available nitrogen. The final treatment was a control which mimicked conventional sod maintenance techniques including synthetic nitrogen fertilizer. Biosolids were incorporated to a depth of 5 cm and plots were seeded with Kentucky bluegrass (Poa pratensis). Stand density, turf color, and soil volumetric moisture content were measured weekly during establishment in 2009 and 2010. Once turf established measurements included turf quality, turf color, clipping yield, soil moisture, and sod tensile strength. Soil coring to a 30 cm depth in 10 cm increments was performed prior to treatment application and again one year after biosolids were applied to track the annual change in soil elemental composition. Data show that all rates and sources of biosolids result in similar establishment as the standard sod production practice, which consisted of inorganic fertilizer applied annually at 250 kg N ha^-1. Turf quality and color increased with N fertility and were greatest when cake was applied at 500 or 1000 kg ha^-1 of plant available N, though not statistically different than the standard practice. Sod strength increased with decreasing nitrogen fertility and was greatest for the 250 kg N ha^-1 application of cake and mix. Preliminary soil testing results show that increases in soil P may limit the application rate of biosolids. These results suggest that biosolids-based sod production can meet or exceed current agronomic goals for sod production in Wisconsin.