The Effect of Biosolids On Kentucky Bluegrass Sod Production In Wisconsin.

The land application of municipal biosolids can provide turfgrass with essential nutrients, reducing or even replacing the need for synthetic fertilizer. Incorporation of biosolids may also mitigate the loss of soil from fields during sod 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 N. The final treatment was a control which mimicked conventional sod maintenance techniques including synthetic fertilizer applied at 265 kg N ha^-1 cycle^-1. Biosolids were incorporated to a depth of 5 cm and plots were seeded with Kentucky bluegrass (Poa pratensis). The experiment was first performed in 2009 and repeated again in 2010 on a second set of plots which had already gone through one full biosolids-based sod production cycle. Biosolids did not reduce turf establishment density compared to the control in 2009 or 2010. Season long turf visual quality was similar for biosolids cake applied at an estimated 500 kg N ha^-1 and the synthetic control. At the time of sod harvest no statistical difference in sod tensile strength was found between cake and the synthetic control. Results show that standard sod production and harvest resulted in soil removal of 78 Mg ha^-1. Biosolids applied at a rate of 500 kg N ha^-1 reduced soil loss to 72 and 33 Mg ha^-1 for the cake and mix, respectively. These results suggest that biosolids-based sod production has the potential to meet or exceed current agronomic goals for sod production in Wisconsin by balancing visual quality, sod strength, and environmental stewardship.