Reducing NH3, N2O and % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX!% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaeOtaiaab+% eadaqhaaWcbaacbaGaa83maaqaaiabgkHiTaaaaaa!3967! $${\text{NO}}_3^ - $$ –N losses from a pasture soil with urease or nitrification inhibitors and elemental S-amended nitrogenous fertilizers

Abstract

A 3-month field experiment comparing nitrogen (N) losses from and the agronomic efficiency of various N fertilizers was conducted on a sandy loam (Typic Hapludand) soil at Ruakura AgResearch farm, Hamilton, New Zealand during October to December 2003. Three replicates of seven treatments: urea, urea + the urease inhibitor N-(n-butyl) thiophosphoric triamide (trade name Agrotain), urea + Agrotain + elemental sulphur (S), urea + double inhibitor [DI; i.e., Agrotain + dicyandiamide (DCD)], diammonium phosphate (DAP), DAP + S, each applied at 150 kg N ha−1, and control (no N). After fertilizer application, soil ammonium ( $$ \operatorname{NH} ^{ + }_{4} $$ ) and nitrate ( $$ \operatorname{NO} ^{ - }_{3} $$ ) concentrations (7.5-cm soil depth), ammonia (NH3) volatilization, nitrate ( $$ \operatorname{NO} ^{ - }_{3} $$ ) leaching, nitrous oxide (N2O) emission, pasture dry matter, and N uptake were monitored at different timings. Urea applied with Agrotain or Agrotain + S delayed urea hydrolysis and released soil $$ \operatorname{NH} ^{ + }_{4} $$ at a slower rate than urea alone or urea + DI. Urea applied with DI increased NH3 volatilization by 29% over urea alone, while urea + Agrotain and urea + Agrotain + S reduced NH3 volatilization by 45 and 48%, respectively. Ammonia volatilization losses from DAP were lower than those from urea with or without inhibitors. Total reduction in $$ \operatorname{NO} ^{ - }_{3} $$ leaching losses for urea + DI and urea + Agrotain compared to urea alone were 89% and 47%, respectively. Application of S with urea + Agrotain reduced $$ \operatorname{NO} ^{ - }_{3} $$ leaching losses by an additional 6%. Nitrous oxide emissions were higher from the DAP and urea alone treatments. Urea applied with DI and urea + Agrotain reduced N2O emissions by 37 and 5%, respectively, over urea alone. Compared to urea alone, total pasture production increased by 20, 17, and 15% for urea + Agrotain + S, urea + Agrotain, and urea + DI treatments, respectively, representing 86, 71, and 64% increases in N response efficiency. Total N uptake in urea + Agrotain, urea + Agrotain + S, and urea + DI increased by 29, 22, and 20%, respectively, compared to urea alone. These results suggest that the combination of both urease and nitrification inhibitors may have the most potential to reduce N losses and improve pasture production in intensively grazed systems.