Dicyandiamide slows nitrification in dairy cattle urine patches: effects on soil solution composition, soil pH and pasture yield

Decreasing the production of nitrate-N (NO3--N) in cattle urine patches may reduce the environmental impacts of pastoral agriculture. This paper reports the effects of the nitrification inhibitor dicyandiamide (DIDIN) on No-3(-)-N and ammonium-N (NH4+-N) production, soil pH and pasture yield in urine-amended and control soil under field conditions. In control plots, DIDIN application did not affect NO3--N, NH4+-N, pH or pasture yields. In urine-amended plots, DIDIN application significantly (P < 0.05) reduced peak NO3--N concentrations, the amount of NO3--N leached, hence decreasing the potential for denitrification losses. Conversely, soil NH4+-N concentration decreased more gradually when urine was amended DIDIN which increased the opportunity for greater immobilization to occur. Differences in NO3--N and NH4+-N concentrations between urine-amended treatments were also reflected by increases in soil pH but not pasture yields. (C) 2002 Elsevier Science Ltd. All rights reserved.