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 (NO 3 –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 m 3 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 (NO 3 –N), ammonium nitrogen (NH 4 –N), total phosphorus (TP), total dissolved P (TDP), and ortho‐phosphate (OP). Compost application of 99 m 3 ha −1 reduced bulk density, and increased water retention and P, K, Fe, and Mn concentrations in the surface soil. Compost applications of 66 m 3 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, NO 3 –N, TP, TDP, and OP in runoff were not different among treatments. However, all compost treatments did increase NH 4 –N concentrations in runoff. There were no differences in soil NO 3 –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 NH 4 –N levels in runoff.