Comparing the effectiveness and longevity of the urease inhibitor N-(2-nitrophenyl) phosphoric triamide (2-NPT) with N-(n-butyl) thiophosphoric triamide (nBTPT) in reducing ammonia emissions from cattle urine applied to dairy-grazed pasture soils

Abstract

The objective of this laboratory incubation study was to assess the effectiveness and longevity of urease inhibitor N-(2-nitrophenyl) phosphoric triamide (2-NPT), along with the commonly used N-(n-butyl) thiophosphoric triamide (nBTPT), in reducing ammonia (NH3) emissions from cattle urine applied to pasture soils. It was hypothesised that 2-NPT would be effective as a longer-lasting inhibitor to reduce emissions after the deposition of urine during multiple grazing events. Two dairy-grazed pasture soils (Fluvisol, Rangitikei loamy sand (RLS) and Andosol, Egmont black loam (EBL)) with contrasting organic carbon levels and urease activity were used. The following treatments were applied to the soils at the start of the experiment: no inhibitor, nBTPT-low, 2-NPT-low, 2-NPT-medium and 2-NPT-high. Urine-N was applied to all the treatments at four stages: immediately before inhibitor application (Stage A), 29 days after inhibitor application (Stage B), 56 days after inhibitor application (Stage C) and 29 days and again 60 days after inhibitor application (Stage D); NH3 emissions were measured up to Day 31 after each urine application. The low, medium and high application rates of inhibitors were determined based on achieving 0.025%, 0.050% and 0.075% of quantity of urine-N applied in Stage A respectively. For the no inhibitor treatment, the proportion of total applied N in urine that was emitted as NH3 for the different stages ranged from 35.8% to 50.5% for RLS soil and from 14.2% to 26.7% for EBL soil. For Stage A, both inhibitors equally reduced NH3 emissions from applied urine in both soils (23.7–27.3% for the RLS and 20.6–27.2% for the EBL). For Stage B, significant reductions (4.2–13.4%) in NH3 emitted was observed only from RLS soil, with there being a significantly greater reduction from 2-NPT than from nBTPT, and 2-NPT continued to reduce NH3 emissions at Stage C (5.6–7.4%). There was no reduction in emissions during Stage D by either of the inhibitors. The results of this study suggest that 2-NPT can extend the longevity of urease inhibition and reduce NH3 emissions compared with the more commonly used inhibitor nBTPT in dairy-grazed pasture soils.

Three-dimensional dynamics of nitrogen from banded enhanced efficiency fertilizers

“…While rapid leaching was unlikely in this low permeability soil, it is clear that at least some urea-N had moved into layers below the fertilizer band by 21 DAF. The relative immobility of banded NBPT in soils of high-clay and OM content has been recently identified by Janke (2020) and is likely a dominant factor in the rapid 'loss-of-function' observed in this and other studies (Watson et al 1994;Adhikari et al 2019). Soluble urea-N may diffuse and/ or move with mass flow, creating an asynchrony of inhibitor and substrate location that reduces the effectiveness of NBPT.…”

Potential application of urease and nitrification inhibitors to mitigate emissions from the livestock sector: a review

“…The application of NPT has been shown to lower NH3 volatilization by 89% after 19 days of incubation [39], and depending on the soil characteristics, it also has greater longevity than NBPT [40]; therefore, the inhibitory effect of 2-NPT may last longer than that of NBPT. However, currently, 2-NPT is still on a laboratory-scale production; therefore, it is not easily available in the market and for field purposes.…”

Controlled-release N fertilizer to mitigate ammonia volatilization from double-cropping rice

“…-N) in floodwater, soil pH, and temperature (Liu et al 2007;Tian et al 2001). A recent study by Adhikari et al (2019) observed high pH buffering capacity of soil with higher organic matter content and vice versa, suggesting influence of organic matter on NH 3 emissions. Thus, investigation of the behavior of NH 3 volatilization under different environmental conditions is vital to increase N use efficiency and to reduce the environmental pollution specially for paddy fields conditions (Liu et al 2015).…”