Relationship of traditional parameters of compost stability to turfgrass quality

Abstract

A preliminary study was conducted to assess the relationship of traditional operational parameters of wastewater sludge composting (such as C: N ratio, and respiration rate) to the quality of established turfgrass following compost application. Compost was sampled at five different stages of an in‐vessel process, and applied at two rates (9700 and 4850 kg ha^‐1) to established tall fescue and also to a mixed sward of perennial ryegrass and Kentucky bluegrass. Surprisingly, no phytotoxicity was observed in any of the turfgrasses at either rate of application, even for the wastewater sludge which had only been composting for approximately 11 days. In all treatments, positive effects of increased growth and enhanced green colour were observed following compost application. The field data suggest a quick nitrogen release effect from the applied compost. Visual difference between treated and non‐treated plots were nearly indistinguishable 32 days after application. These observations suggest that compost may be applied to established turfgrass after undergoing a relatively short high rate phase of composting. Traditional parameters suggested that the sludge was approaching maturity as it went along the length of the composting bay, however a delayed or secondary stage of oxidation was observed in this study when additional moisture was added to the compost mixture. This observation further emphasizes the need for careful moisture management.