Windrow temperatures and chemical properties during active and passive aeration composting of beef cattle feedlot manure

Windrow composting emerged in the mid-1990s as an alternative manure-handling practice in Alberta’s cattle feedlot industry. This study compared two composting methods: active (turning) and passive aeration. Temperatures were monitored over the first 90 d and chemical properties over 188 d of composting. Pre- vs. post-turning sampling of the active treatment was also compared. Mean daily temperature was warmest at the bottom windrow location (53.6ºC) and coolest at the top (46.4ºC) in the active treatment, but warmest at the top (44.1ºC) and coolest at the bottom (33.9ºC) in the passive treatment. Final compost from the passive treatment had significantly higher total N (TN), total C (TC), electrical conductivity (EC), Na, and Cl than the active treatment. There were no significant treatment effects on C:N ratio, NH 4 -N, NO 3 -N, total P (TP), Kelowna-extractable P (KEP), pH, Ca, Mg or K. Both treatments showed substantial and non-significantly different C (71–80%) and N (44–58%) losses. Pre- versus post-turning sampling showed significant differences for some compost parameters, notably soluble salts. After the thermophilic phase, the passive treatment appeared only partially composted. Additional disadvantages of the passive treatment included lower windrow temperatures, which may fail to reduce pathogens, and higher EC, which could potentially limit the end use of passively aerated compost. Key words: Cattle manure, composting, active aeration, passive aeration, nutrients