Topdressing Turf with Composted Manure Improves Soil Quality and Protects Water Quality

Compost can improve soil properties when incorporated into soil; however, little information is available regarding impacts of compost topdressing. Objectives of this study were to evaluate the effects that topdressing composted dairy manure onto Kentucky bluegrass (Poa pratensis L.) has on: (i) soil physical properties, (ii) soil chemical properties, (iii) soil nitrate (NO3–N) and P concentrations below the rootzone, (iv) total runoff and sediment losses, and (v) N and P concentrations in runoff. Plots were topdressed with compost at 0, 33, 66, and 99 m3 ha−1 Saturated hydraulic conductivity, bulk density, water retention, and soil nutrient levels were measured. A rainfall simulation was conducted, and runoff was collected and analyzed for total nitrogen (TN), nitrate nitrogen (NO3–N), ammonium nitrogen (NH4–N), total phosphorus (TP), total dissolved P (TDP), and ortho‐phosphate (OP). Compost application of 99 m3 ha−1 reduced bulk density, and increased water retention and P, K, Fe, and Mn concentrations in the surface soil. Compost applications of 66 m3 ha−1 or greater raised soil electrical conductivity (EC); however, this increase in soil EC did not negatively impact turf quality. Rates of runoff and erosion and concentrations of TN, NO3–N, TP, TDP, and OP in runoff were not different among treatments. However, all compost treatments did increase NH4–N concentrations in runoff. There were no differences in soil NO3–N or available P levels below the root zone. Topdressing composted manure onto established turf improved soil physical properties and nutrient concentrations without increasing nutrient runoff, with the exception of increased NH4–N levels in runoff.