Addition Of N-butyl) Thiophosphoric Triamide Research Articles

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

AbstractMid‐ 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.

Alternatives to regular urea for abating N losses in lettuce production under sub-tropical climate

Alternative fertilization practices are needed for reducing gaseous and leaching N losses at high urea application rates. The objective of this study was to compare gaseous N emissions (N2O and NH3) and NO3 − concentrations in the soil solution during two successive lettuce cropping seasons under contrasting fertilization practices. Treatments were fertilization with regular urea (U), urea treated with urease [N-(n-butyl) thiophosphoric triamide (NBPT)] and nitrification [dicyandiamide (DCD)] inhibitors (UIs), non-acidified pig slurry compost (PSC), acidified pig slurry compost (APSC), and an unfertilized control (C). Acidification of pig slurry during composting had no impact on soil cumulative N2O emissions during the cropping seasons. The use of composts resulted in emission factors (EFs) (PSC, 0.09% of applied N; APSC, 0.16%) an order of magnitude smaller than with regular urea (1.63%). Similarly, adding NBPT and DCD to urea reduced the N2O EF from 1.63 to 0.37% of applied N and fertilizer-induced NH3 emissions from 30.2 to 3.4% of applied N. Composts and UI resulted in yield-scaled N2O emissions that were 33 to 49% lower than the unfertilized control and 64 to 73% lower than the regular urea estimates, indicating a greater efficiency of supplied N with composts and UI. Nitrate concentration of the soil solution (at 0.1 and 0.3 m) in PSC, APSC, and UI plots was similar to the control and up to 17 times lower than with regular urea, indicating reduced risks for leaching losses. We conclude that, as compared to regular urea, the use of composted pig slurry, with and without acidification, and the addition of NBPT and DCD inhibitors to urea are good practices to reduce environmental N losses from lettuce production under sub-tropical climate.

Late‐Fall, Winter and Spring Broadcast Applications of Urea to No‐Till Winter Wheat I. Ammonia Loss and Mitigation by NBPT

Core Ideas Urea volatility was greater following late‐fall and winter applications to cold soils compared with spring applications to warmer soils. NBPT reduced cumulative NH3 loss from urea by 66%. Urea applications in the late‐fall and winter resulted in prolonged periods of NH3 flux. Surface urea applications in the late‐fall, winter, or early‐spring are common in Montana, but N applied at these timings is susceptible to volatilization. This study was conducted to quantify and contrast ammonia (NH3) loss from urea and urea plus N‐(n‐butyl) thiophosphoric triamide (NBPT) following late‐fall, winter, and spring applications (100 kg N ha–1). Experiments were run over 3 yr in farmer‐cooperator fields (>60 ha) under no‐till winter wheat (Triticum aestivum L.)–chemical fallow management. Ammonia emissions were quantified by the integrated horizontal flux method with samplers placed on a mast in the center of circular plots (20‐m radius). Prolonged periods of modest NH3 flux (≤33 g N ha–1 h–1) were found following late‐fall (87–106 d) and winter (48–62 d) urea applications before flux fell to nominal levels (≤3 g N ha–1 h–1). In contrast, NH3 flux following spring urea was generally lower in intensity (≤7 g N ha–1 h–1) and shorter in duration (14–30 d). Cumulative NH3 loss (% applied N) from urea was greater (P < 0.05) for late‐fall (16.4%) and winter (11.4%) than for spring (2.0%) applications. The weather pattern of light (≤6 mm), scattered precipitation events from December throught March vs. larger precipitation events (≥12 mm) in April and May was an important factor which helped explained this response. Addition of NBPT (1 g kg–1) to urea reduced cumulative NH3 loss by 65.6%. Urea applications during the over‐winter period (December–March) should be avoided, in favor of spring applications to minimize NH3 loss.

INFLUENCE OF HIGH TEMPERATURE AND UREA FERTILIZATION WITH N-(N-BUTYL) THIOPHOSPHORIC TRIAMIDE AND DICYANDIAMINDE ON COTTON GROWTH AND PHYSIOLOGY

The objective of this growth chamber study was to evaluate the effect of adding N-(n-butyl) thiophosphoric triamide (NBPT) and dicyandiaminde (DCD) to urea fertilizer, on the physiology and growth of cotton (Gossypiumhirsutum L.) under normal and high temperatures. Treatments consisted of two day temperature regimes, 30°C and 38°C, and five nitrogen fertilization applications: unfertilized control, 125 kg ha−1 of urea, 93 kg ha−1 of urea, 93 kg ha−1 urea + NBPT, and 93 kg ha−1 urea + NBPT + DCD. The addition of NBPT to urea fertilizer had positive effects on leaf chlorophyll, leaf area, dry matter, nitrogen (N) uptake, and N use efficiency. The absence of a significant interaction effect indicated that N fertilization was not influenced by temperature. Deficiency of N significantly decreased leaf chlorophyll, increased glutathione reductase, decreased protein and increased leaf nitrate reductase. Physiological changes under high temperature included increased plant N uptake, glutamine synthetase, leaf chlorophyll, protein content, plant height and leaf area were due to high N uptake and utilization.

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

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 .

A Comparison of a Maleic‐Itaconic Polymer and N‐(n‐butyl) Thiophosphoric Triamide as Urease Inhibitors

A maleic‐itaconic polymer (MIP) is claimed to inactivate soil urease by nickel removal from the enzyme. Four studies were conducted to compare the urease inhibition properties of two commercial formulations of MIP with a commercial formulation of N‐(n‐butyl) thiophosphoric triamide (NBPT). In the first study, addition of MIP at 1, 5, or 50 mg kg–1 provided 0 to 2% inhibition of urea hydrolysis, averaged across three soils. At 500 mg kg–1, MIP inhibited urea hydrolysis by 7 to 9%, averaged across three soils. By contrast, addition of NBPT at 1 or 5 mg kg–1 inhibited urea hydrolysis by an average of 64 and 72%, respectively. In a second study, 13 carboxylic acids of known nickel sequestration properties, two MIP formulations, and NBPT were evaluated as soil urease inhibitors. Averaged across three soils, MIP and the other carboxylic acids provided &lt;5% inhibition of urea hydrolysis when applied at 50 mg kg–1. Addition of NBPT at 1 and 5 mg kg–1 provided an average of 62 and 72% inhibition. In two additional studies using purified jackbean [Canavalia ensiformis (L.) DC.] urease in the absence of soil, NBPT provided complete inhibition at a concentration of 1 mg L–1 in the reaction mixture. Adding MIP at rates up to 100 mg L–1 either did not inhibit urease, or stimulated urea hydrolysis. It was concluded that MIP was not an effective inhibitor of soil or jackbean urease. It was also concluded that nickel sequestration by carboxylic acids is an unlikely mode of action for soil urease inhibition.

Inhibition of urease activity in flooded soils: Effect of thiophosphorictriamides and phosphorictriamides

The effectiveness of two thiophosphorictriamides, [N-(n-butyl)thiophosphorictriamide (NBPT) and thiophosphoryltriamide (TPT)], and three phosphorictriamides, [N-(n-butyl)phosphorictriamide (NBPTO), phosphoryltriamide (PT) and cyclohexylphosphorictriamide (CHPT)], to inhibit urease activity in flooded soils in the presence or absence of photosynthetic algae was evaluated in laboratory experiments. Both TPT and its oxygen analogue PT were poor inhibitors of urease activity in these flooded soils in the presence or absence of algae. In the absence of photosynthetic algae, the rate of urea hydrolysis was retarded slightly by the addition of NBPT. However, in the presence of algae the capacity of NBPT to inhibit urease activity was enhanced considerably. It appears that the oxygen produced by the photosynthetic algae resulted in more rapid conversion of the pro inhibitor NBPT to NBPTO, which is the effective urease inhibitor. The phosphorictriamides CHPT and NBPTO were significantly better than the other compounds for retarding urease activity, and CHPT ranked above NBPTO as a urease inhibitor. In the presence of photosynthetic algae the effectiveness of these inhibitors appears to be reduced, and this seems to be related to algal uptake of nitrogen and more rapid volatilization of ammonia and nitrification. The results suggest that the phosphorictriamides CHPT and NBPTO in conjunction with an algicide, to control the growth of floodwater algae, have the potential to considerably reduce ammonia loss from flooded rice soils.

Effects of phosphoroamides on ammonia volatilization and nitrite accumulation in soils treated with urea

We compared the effects of N-(n-butyl) thiophosphoric triamide (NBPT), N-(diaminophosphinyl)-cyclohexylamine (DPCA), phenylphosphorodiamidate (PPD), and hydroquinone on transformations of urea N in soils. The ability of these urease inhibitors to retard urea hydrolysis, ammonia volatilization, and nitrite accumulation in soils treated with urea-decreased in the order NBPT > DPCA ≫ PPD > HQ. When five soils were incubated at 30°C for 14 days after treatment with urea (1 mg urea N g−1 soil), on average, the gaseous loss of urea N as ammonia and the accumulation of urea N as nitrite were decreased from 52 to 5 % and from 11 to 1%, respectively, by addition of NBPT at the rate of 10 μg g−1 soil (0.47 parts of NBPT per 100 parts of urea). The data obtained support previous evidence that NBPT is more effective than PPD for reduction of the problems encountered in using urea as a fertilizer and deserves consideration as a fertilizer amendment for retarding hydrolysis of urea fertilizer in soil.