2017 ASHS Annual Conference

Compost, a stabilized form of organic matter derived from the biological decomposition of plant, animal, or human waste, has been traditionally used for purposes of fertilization and soil amelioration. Biochar is produced through anaerobic heating of plant biomass to produce extremely stable carbon in the form of amorphous graphene sheets. Both technologies increase soil organic matter (SOM), which can convey improvements in soil water and nutrient retention, and soil structure. Biochar is more highly resistant to degradation and recent work has suggested a synergistic effect between biochar and compost materials. A field study was conducted at University of California Riverside in 2014 and a greenhouse replication in 2015 to evaluate the effects of compost, biochar, and combined biochar and compost amendments on the establishment rate of tall fescue (Schedonorous arundinaceous). Biochar and compost amendments were incorporated on 16 April 2014 while tall fescue was seeded on 5 May 2014. The study was replicated in the greenhouse beginning 13 May 2015, when pots were seeded. Field plots were amended to a depth of 15 cm with either greenwaste compost (5.1 or 10.2 cm), biosolids compost (5.1 cm), biochar (2.2, 11.2, or 22.4 t ha^-1), or combinations of biochar and greenwaste compost (5.1 cm compost, 11.2 t ha^-1biochar). The greenhouse study used identical amendments and rates, but included an additional treatment combining biosolids compost with biochar as biosolids compost was shown to most negatively impact turfgrass establishment, most likely due to high salinity levels (20 dS/m). Seedling density was measured biweekly, subjected to Digital Image Analysis (DIA), and used to construct sigmoidal regression comparing establishment rates, turf cover at 50 and 75 days after seeding (DAS), and final cover at each study’s conclusion. Compost-amended soils resulted in slower establishment measured as reductions in live turf cover. Combining greenwaste compost with biochar did not improve performance compared to compost alone, but the combined addition of biosolids compost with biochar resulted in improved establishment rates compared to biosolids alone. While soils amended only with biosolids compost reduced establishment rates compared to controls, including biochar in the amendment increased establishment rates, making them comparable to controls. These results suggest that combining biochar with compost amendments in turfgrass culture can reduce negative impacts of compost amendments on turfgrass establishment.