Efficacy of a new<i>N</i>-(<i>n</i>-butyl) thiophosphoric triamide formulation in reducing ammonia volatilization from urea-based fertilizers

Kumaragamage

2020

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The addition of nitrification inhibitor (NI) with a urease inhibitor, N-(n-butyl) thiophosphoric triamide (NBPT), has been reported to offset the reduction of ammonia volatilization by NBPT. An incubation study was conducted to investigate the interaction between NBPT and NI (3,4-dimethyl pyrazole phosphate) on hydrolysis of urea in five soils with a range of physico-chemical properties. Untreated urea (UR), NBPT treated urea (UR NBPT), or NBPT+NI treated urea (UR DI) were surface-applied (250 kg N ha −1) to each soil. The soils were incubated (21 • C) and destructively sampled nine times during a 22-day period. Urea hydrolysis rate (k; d −1) was measured by the disappearance of urea with time and modeled with a first-order kinetic. The value of k was in the order of UR (0.321) > UR DI (0.183) > UR NBPT (0.151) across the five soils. While the urease inhibitor, NBPT, significantly reduced k in each soil, the addition of a NI with NBPT significantly decreased the ability of NBPT to inhibit urea hydrolysis by an average of 21% across the soils. We found that NI significantly reduced the half-life of urea by about 1 d when compared with NBPT alone. Principal component analysis showed that k did not depend on any of the soil properties, rather, it depended on the type of treatment. Net nitrification rate constant was significantly greater in UR than UR NBPT in loam and clay soils but not different in sandy loam soils. We conclude that the often-reported increase in ammonia volatilization with the double inhibitor relative to NBPT alone may not only be due to the persistence of ammonium but may also be due to an increased rate of urea hydrolysis in the presence of a NI. 1 INTRODUCTION Globally, urea accounts for about 50% of nitrogen (N) fertilizers that are applied to agricultural and horticultural Abbreviations: DI, double inhibitor; NBPT, N (n-butyl) thiophosphoric triamide; NI, nitrification inhibitor; UR DI , double inhibitor treated urea; UR NBPT , NBPT treated urea. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Section: Resultssupporting

confidence: 78%

Section: Urea Hydrolysis Rate Constantcontrasting

confidence: 51%

Section: Methodsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Nitrification inhibitor reduces the inhibitory effect of N‐(n‐butyl) thiophosphoric triamide (NBPT) on the hydrolysis of urea

Kumaragamage

2020

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“…To reduce ammonia volatilization from surface‐applied urea‐based fertilizers, farmers have the option to coat their urea with urease inhibitors such as NBPT. The urease inhibitor NBPT is known to reduce ammonia volatilization effectively under different soil and environmental conditions (Lasisi et al., 2019; Modolo, da‐Silva, Brandão, & Chaves, 2018; Sigurdarson, Svane, & Karring, 2018). In addition to coating urea with NBPT, farmers may also use a NI along with the NBPT to inhibit nitrification.…”

Section: Introductionmentioning

confidence: 99%

Efficiency of fall versus spring applied urea‐based fertilizers treated with urease and nitrification inhibitors II. Crop yield and nitrogen use efficiency

Kumaragamage

2021

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The urease inhibitor [N‐(n‐butyl) thiophosphoric triamide (NBPT)] and the nitrification inhibitor (NI) 3,4‐dimethyl pyrazole phosphate have been reported to conserve urea‐based N fertilizers by reducing N losses. However, their effects on crop yield and N uptake are inconsistent and fall‐applied N fertilizers are usually less efficient than spring applications. We conducted a 2‐yr field study on contrasting soils [Carman sandy loam (CSL) and Portage clay loam (PCL)] on the effects of NBPT with and without NI on grain yield, grain N removal, and crop N uptake from fall and spring surface‐applied urea‐based fertilizers. Fertilizer treatments (75 or 100 kg N ha−1) were urea and urea ammonium nitrate (UAN) with and without NBPT or NBPT + NI. Canola (Brassica napus L.) and wheat (Triticum aestivum L.) yield, N removal, and N uptake were not consistently greater for urea and UAN treated with inhibitors than for untreated urea and UAN. The inhibitors’ effect on yield and N uptake was observed in urea treated with NBPT in CSL but not PCL. Although agronomic efficiency was significantly greater for spring‐applied untreated urea or UAN than fall‐applied urea or UAN with and without inhibitors in PCL, no significant difference appeared between fall‐applied urea or UAN treated with inhibitors and spring‐applied untreated urea or UAN in CSL. The N conserved by the inhibitors did not appear in the soil as nitrate‐N. Although inhibitors may reduce N losses, their use to increase yield and bridge the efficiency gap between fall‐ and spring‐applied urea‐based fertilizers may be site‐specific.

Efficiency of fall versus spring applied urea‐based fertilizers treated with urease and nitrification inhibitors I. Ammonia volatilization and mitigation by NBPT

Qiang

et al. 2020

Mid‐ or late‐fall N fertilization is usually recommended on the Canadian prairies to reduce N losses from fall‐applied N. Yet, N fertilizers are less efficient when applied in mid‐ or late fall than in spring on crop yield. Ammonia volatilization from N fertilizers is one of the reasons for the low N use efficiency. We conducted a 2‐yr study to quantify and contrast the efficacy of a urease inhibitor, N‐(n‐butyl) thiophosphoric triamide (NBPT), with and without a nitrification inhibitor, 3,4‐ dimethylpyrazole phosphate (NI), in reducing NH3 volatilization from fall‐ and spring‐applied urea‐based fertilizers in two contrasting soils. Treatments consisted of surface‐applied urea and urea–NH4NO3 (UAN) with and without NBPT or NBPT + NI (double inhibitor, DI). We measured NH3 volatilization with acid‐charged disks during 21 (fall) or 28 (spring) d. Total NH3 volatilization (percentage of applied N) from untreated urea and UAN across sites ranged from 7 to 22% with fall application and from 3 to 29% with spring application. Addition of NBPT only or DI to urea or UAN reduced NH3 volatilization by 61 to 74% in the fall and 4 to 69% in the spring across site‐years. We found that the reduction of NH3 volatilization by NBPT was significantly greater in the fall (65%) than in the spring (40%) and with urea (61%) than with UAN (43%). Our study showed that (a) significant NH3 volatilization could occur from surface‐applied urea‐based fertilizers even under late‐fall temperatures and (b) NBPT reduced NH3 volatilization from fall‐ as well as spring‐applied urea‐based fertilizers. Therefore, farmers are encouraged to treat their urea‐based fertilizers with NBPT when considering surface application.