Effects of a urease inhibitor and aluminium chloride alone or combined with a nitrification inhibitor on gaseous N emissions following soil application of cattle urine

Abstract

Addition to soil of separated cattle-urine obtained from housing with urine-faeces segregation systems is an important source of gaseous nitrogen (N) emissions. This study aimed to evaluate the effect of adding different concentrations of the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) and aluminium chloride (AlCl 3 ), alone or combined with the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP), on gaseous N losses and N transformations in soil amended with cattle-urine. Using laboratory incubations soil was amended with cattle-urine (200 kg total N ha −1 ) containing NBPT (0.1 or 1.0%) or AlCl 3 (0.5 or 1.0%) either as a single additive or combined with 0.5% DMPP. Three additional treatments were included: soil only (Control), soil amended only with cattle-urine and soil amended with cattle-urine and DMPP. The addition of NBPT at 1% significantly delayed urea hydrolysis during the first 4-d after urine application comparatively to treatments receiving AlCl 3 . Nitrification was inhibited by addition of DMPP, with no further effect ( P > 0.05) when DMPP was combined with NBPT or AlCl 3 . The AlCl 3 treatment had no effect on urea hydrolysis or nitrification. The combination of DMPP with NBPT or AlCl 3 increased ( P < 0.05) NH 3 emissions and reduced ( P < 0.05) NO and N 2 O emissions compared with urine alone. It was concluded that NBPT was more effective at reducing gaseous N emissions from cattle-urine applications than AlCl 3 , and that NBPT alone was more effective than NBPT combined with DMPP. No advantages were gained from the combination of one of these additives with DMPP on total gaseous N emissions. • The effects of NBPT or AlCl 3 alone or combined with DMPP on emissions were evaluated. • DMPP with either NBPT or AlCl 3 had the same effect on nitrification as DMPP alone. • Increasing the concentration of NBPT or AlCl 3 did not significantly reduce gaseous N emissions. • DMPP with either NBPT or AlCl 3 increased NH 3 emissions and reduced NO and N 2 O emissions. • NBPT, with or without DMPP, was more effective at reducing gaseous N emissions than AlCl 3 .