Effect of timing of joint application of hydroquinone and dicyandiamide on nitrous oxide emission from irrigated lowland rice paddy field

Abstract

A field experiment was conducted to study the effect of timing of joint application of urease inhibitor hydroquinone (HQ) and nitrification inhibitor dicyandiamide (DCD) on N 2O emission from irrigated lowland rice paddy field. Four treatments including Treatment CK (the control with urea alone), HQ/DCD-1 (application of HQ and DCD together with fertilizer before transplanting), HQ/DCD-2 (HQ and DCD with fertilizer at tillering stage) and HQ/DCD-3 (HQ and DCD with fertilizer at panicle initiation stage) were designed and implemented separately during rice growth period. Seasonal peaks of N 2O flux occurred during midseason drainage and significant negative correlation between N 2O flux and water layer depth was observed ( r = −0.69 to −0.75, P < 0.01). Mean N 2O flux was the highest in the control with urea alone, while joint addition of HQ and DCD with urea lowered mean N 2O flux considerably ( P < 0.05). Total N 2O emission during rice growth season in Treatment CK, HQ/DCD-1, HQ/DCD-2 and HQ/DCD-3 was 3.90, 2.98, 1.73 and 3.23 kg N 2O–N ha −1, respectively. Application of HQ and DCD together with basal fertilizer, tillering fertilizer and panicle initiation fertilizer decreased the total N 2O emission by 24%, 56% and 17%, respectively, while increased grain yield by 10%, 18% and 6%, respectively. Effect of application of inhibitors on N 2O emission during the continuous period from incorporation of HQ and DCD to rice harvest was also studied, where results indicating that the highest inhibiting efficiency of inhibitors on N 2O emission was recorded when HQ and DCD applied with fertilizer at tillering stage.