Nitrogen Release from Poppy Waste and Biosolids at Low Temperature

An incubation experiment was conducted over 56 days at 12.5° C and constant soil moisture to compare nitrogen mineralisation between organic soil amendments available to the agricultural industry in Tasmania. Treatments incorporated with soil were poppy mulch (PM, seed head and stem residues after alkaloid extraction), poppy seed waste (PSW, seed residue after oil extraction), anaerobically digested biosolids (ADB), lime amended biosolids (LAB), lime and an unamended control. At day 28, mineralisation of the total nitrogen applied in the ADB, PSW and LAB treatments was 29%, 36% and 44% respectively. Values increased to 35%, 48% and 62% respectively at day 56. However, the PM treatment (and to a lesser extent the lime and control treatments) exhibited a drawdown of nitrate over the same period.