Carbon Dioxide Fluxes In Biosolid-Amended Soils During Turfgrass Establishment.

Biosolids additions to soil may enhance the sustainability of sod production and offset fertilization needs during turfgrass establishment. The effect of biosolids additions on CO2 flux during turf establishment is unknown, and information on CO2 flux of turf systems may be important for C cap-and-trade systems. The objective of our study was to determine the effects of biosolid additions on soil C-flux during turfgrass establishment. A randomized block design with five replications was used to test four rates of biosolids (0, 100, 200, 400 kg Plant Available N ha-1) incorporated into silt loam soil. PVC cylinders containing soil substrates were maintained in greenhouse conditions; half were sown with Kentucky bluegrass (Poa pratensis L.). Carbon dioxide flux was measured at two week intervals using an infra-red gas analyzer for 16 weeks. Repeated measures analysis was used to determine treatment effects. Biosolids rates did not affect gross photosynthesis (Pg), net photosynthesis (Pn), or dark respiration (Rd). Gross photosynthesis and Rd rates increased as bluegrass biomass increased over 16 weeks. Vegetation more than doubled Rd rates compared to non-vegetated treatments, increasing from 2.6 umol m-2s-1 on day 27 of the study to 6.5 umol m-2s-1 on day 119 of the study. Net photosynthesis was only positive during a two week period mid-way through the study, after which increasing Rd reduced Pn to negative values, likely due to increasing temperatures. Biosolids additions to soils should have no practical impact on CO2 flux during turf establishment.