Effect of temperature on dicyandiamide (DCD) longevity in pastoral soils under field conditions

Abstract Data were analysed from five trials begun in autumn at a field site and a relationship between time for concentration of the nitrification inhibitor dicyandiamide (DCD) in soil to halve ( t ½ , days) and the mean soil temperature ( T , °C) was developed: t ½  = 54–1.8  T . For example, when T was 8 and 16 °C, t ½ was 39 ± 6 and 25 ± 3 days (±95% confidence limit), respectively. Previously, under laboratory conditions at equivalent temperatures, the corresponding values of t ½ were 86 ± 31 and 44 ± 24 days. Thus, the proportional responses of t ½ to increasing T from 8 to 16 °C were similar, but under field conditions t ½ was about half that under laboratory conditions.