N-丁基硫代磷酰三胺对淹水土壤脲酶动力学特征的影响

研究了淹水状态下脲酶抑制剂N-丁基硫代磷酰三胺(NBPT)对东北4种典型土壤(黑土、白浆土、棕壤、褐土)脲酶动力学参数的影响。结果表明,NBPT对土壤脲酶动力学参数的作用程度受土壤类型、培养时间及其交互作用的显著影响。与对照相比,NBPT使土壤脲酶米氏常数(Km)增加,最大反应速率(Vmax)和Vmax/Km降低,表明NBPT对土壤脲酶的作用机理属于典型的混合型抑制。随培养时间延长,土壤脲酶Km降低,Vmax和Vmax/Km升高,表明NBPT对脲酶的抑制效力逐渐减弱。黑土、白浆土脲酶Km值小于棕壤和褐土,而Vmax则大于棕壤和褐土,表明土壤肥力水平能够影响土壤脲酶的动力学参数。相关分析表明,土壤脲酶Km与粘粒和粉粒含量呈显著正相关关系,与pH值呈显著负相关关系;而Vmax和Vmax/Km的相关性则正好与此相反。     

Enhanced-efficiency nitrogen fertilizers reduce winter losses of nitrous oxide,but not of ammonia,from no-till soil in a subtropical agroecosystem

Nitrogen (N) gas losses can be reduced by using enhanced-efficiency N (EEN) fertilizers such as urease inhibitors and coating technologies. In this work, we assessed the potential of EEN fertilizers to reduce winter losses of nitrous oxide (N₂O-N) and ammonia (NH₃-N) from a subtropical field experiment on a clayey Inceptisol under no-till in Southern Brazil. The EEN sources used included urea containing N-(n-butyl) thiophosphoric triamide (UR+NBPT), polymer-coated urea (P-CU) and copper-and-boron-coated urea (CuB-CU) in addition to common urea (UR) and a control treatment without N fertilizer application. N₂O-N and NH₃-N losses were assessed by using the static chamber method and semi-open static collectors, respectively. Both N₂O-N and NH₃-N exhibited two large peaks with an intervening period of low soil moisture and air temperature. Although the short-term effect was limited to the first few days after application, UR + NBPT urea decreased soil N₂O-N emissions by 38% relative to UR. In contrast, urease inhibitor technology had no effect on NH₃-N volatilization. Both coating technologies (CuB-CU and P-CU) were ineffective in reducing N losses via N₂O production or NH₃ volatilization. The N₂O emission factor (% N applied released as N₂O) was unaffected by all N sources and amounted to only 0.48% of N applied—roughly one-half the default factor of IPCC Tier 1 (1%). Based on our findings, using NBPT-treated urea in the cold winter season in subtropical agroecosystems provides environmental benefits in the form of reduced soil N₂O emissions; however, fertilizer coating technologies provide no agronomic (NH₃) or environmental (N₂O) advantages.     

Effect of N-(n-butyl) thiophosphoric triamide on hydrolysis of urea by plant,microbial, and soil urease

Summary Comparison of the effects of N-(n-butyl) thiophosphoric triamide (NBPT) and phenylphosphorodiamidate (PPD) on hydrolysis of urea by plant (jackbean), microbial (Bacillus pasteurii), and soil urease showed that whereas NBPT was considerably more effective than PPD for inhibiting hydrolysis of urea added to soil, it was much less effective than PPD for inhibiting hydrolysis of urea by plant or microbial urease. Studies to account for this observation indicated that NBPT is rapidly decomposed in soil to a compound that is much more effective than NBPT for inhibition of urease activity and that this compound is N-(n-butyl) phosphoric triamide.     

Nitrogen Fertilization of Soybean Affects Root Growth and Nodulation on Two Soil Types in Mississippi

Greenhouse studies were conducted to evaluate the influence of nitrogen (N) sources [urea + ?N-(n-butyl) thiophosphoric triamide, NBPT (urease inhibitor) and polymer-coated urea (PCU)] and rates on soybean root characteristics, nodule formation, and biomass production on two soil types (silt loam and clay) commonly cropped to soybean in Mississippi. About 15% less belowground biomass was produced in clay soil than in silt loam soil directly corresponding to all other root parameters including root length, root area, root diameter, and nodule number. Pooled across N rates, N additions resulted in 19% and 52% decrease in belowground biomass and number of nodules, respectively, across soils compared to soybean receiving no N. The N rate was the most critical factor as it influenced all root growth parameters. Number of nodules were 24% greater with PCU than urea + NBPT. Nitrogen additions and clay soil negatively impacted soybean root growth, nodulation, and belowground biomass production.

Abbreviations: Polymer-coated urea, PCU; N-(n-butyl) thiophosphoric triamide, NBPT     

Effects of the urease inhibitor N-(n-butyl)phosphorothioic triamide in low concentrations on ammonia volatilization and evolution of mineral nitrogen

Laboratory incubation experiments were conducted to study the influence of increasing concentrations of N-(n-butyl)phosphorothioic triamide (NBPT) on NH₃ volatilization and rate of urea hydrolysis and evolution of mineral N in Ozzano, Rimini and Carpi soils with different physicochemical characteristics. Low concentrations of NBPT reduced NH₃ losses due to volatilization after urea fertilization and the effectiveness of the inhibitor was related to the soil characteristics (e.g. high concentrations of organic C and sand). After 15 days of incubation, no significant reductions of losses were found for any of the NBPT concentrations employed in Rimini soil. The application of NBPT led to a considerable reduction of the formation of nitrite. This process was completely annulled with the highest dose of NBPT (0.5% w/w_urea) in the Carpi soil after 15 days. In Rimini soil, however, the use of NBPT was less effective in influencing nitrite formation. The use of NBPT favoured accumulation of nitrate proportional to the NBPT concentration employed while it had no influence on the NH _inf4 ^sup+ fixation by 2:1 layer silicates. The data obtained support previous evidence that NBPT is effective in reducing the problems encountered in using urea as fertilizer. However, environmental conditions and soil physicochemical characteristics may have an important influence on the effectiveness of NBPT.     

Rate and mode of application of the urease inhibitor N-(n-butyl) thiophosphoric triamide on ammonia volatilization from surface-applied urea

A laboratory study evaluated the effect of rate (0, 100, 250, 500, 750 or 1000 mg/kg) and mode of application of the urease inhibitor N -( n -butyl) thiophosphoric triamide (nBTPT) (coating the urea granule, adding to the urea melt or adding to urea ammonium nitrate (UAN) solutions) on NH₃ volatilization from urea, at three temperatures (5, 15 and 25 °C), with four contrasting soil types. Daily ammonia loss was measured for up to 21 days after surface N application, using ventilated soil enclosures. Ammonia loss from unamended urea varied with soil type and temperature and ranged from 8.2 to 31.9% of the N applied. nBTPT was highly effective in lowering NH₃ volatilization from urea and in delaying the time of maximum rate of loss. The average % inhibition over all soils, temperatures and formulations was 61.2, 69.9, 74.2, 79.2 and 79.8% for the 100, 250, 500, 750 or 1000 mg/kg nBTPT concentration, respectively. The % inhibition with nBTPT was lower at 15 °C compared with at 5 or 25 °C and was lower in UAN solutions than in granular products. There was little difference between the melted and coated granular products in lowering NH₃ loss or in soil N transformations. The stability of nBTPT in urea products was dependent on its mode of application and on the storage temperature. Incorporating nBTPT in the urea melt produced a more homogeneous product with superior stability than coating the urea granule.     

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

Summary 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 g 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.     

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.     

土壤温度和含水量互作对抑制剂抑制氮素转化效果的影响

为比较生化抑制剂组合对土壤氮素转化的抑制效果,揭示不同土壤温度和含水量互作对尿素水解抑制效应的影响。该文采用室内模拟培养方法,研究土壤含水量(60%和80%田间最大持水量,water holding capacity,WHC)和土壤温度(15、25和35℃)互作对生化抑制组合[N-丁基硫代磷酰三胺(N-(n-butyl)thiophosphoric triamide,NBPT)、N-丙基硫代磷酰三胺(N-(n-propyl)thiophosphoric triamide,NPPT)和2-氯-6(三氯甲基)吡啶(2-chloro-6(trichloromethyl)pyridine,CP)在黄泥田土壤中抑制氮素转化效果的影响。结果表明:土壤温度和含水量对生化抑制组合在黄泥田土壤中抑制尿素水解效应显著,以土壤温度影响更大。随着土壤温度增加,尿素水解转化增强,有效作用时间降低,硝化作用增强,脲酶和硝化抑制效应减弱;随着土壤含水量降低,尿素水解转化缓慢,有效作用时间延长,硝化作用减弱,脲酶和硝化抑制效应增强。不同土壤温度和含水量条件下,NBPT/NPPT或配施CP处理有效抑制黄泥田土壤脲酶活性,延缓尿素水解;CP或配施NBPT/NPPT处理有效抑制NH4+-N向NO_3~--N转化,保持土壤中较高NH_4~+-N含量长时间存在。新型脲酶抑制剂NPPT单独施用及与CP配施的土壤尿素水解抑制效果与NBPT相似。黄泥田土壤中生化抑制组合应用最佳的土壤温度和含水量分别为25℃和60%WHC。总之,针对不同土壤温度和含水量条件,在黄泥田土壤中应采用脲酶抑制剂与硝化抑制剂相结合的施肥方式。     

Effect of methods of application on the efficiency of urea broadcast onto lowland rice (Oryza sativa L.)

Summary We evaluated the effect of different methods of application on the efficiency of urea broadcast at a rate of 100 kg N ha^-1 onto lowland rice (Oryza sativa L. var. SPR 60) in a field experiment conducted on a Phimai soil (Fluvic Tropaquepts) during the dry season of 1989. Analysis of the floodwater on the first day after the fertilizer application showed a high initial concentration of urea-N. Addition of the urease inhibitor N-(n-butyl) thiophosphoric triamide (nBTPT), broadcast with the urea into the floodwater, caused an apparent reduction in the rate of urea disappearance and a subsequent accumulation of NH₃–N in the floodwater; this ureas inhibitor also suppressed the rise in floodwater pH, with a resultant reduction in the partial pressure of ammonia (pNH₃) compared with the unamended urea application. The use of nBTPT did not decrease the N loss from broadcast urea not did it increase the grain yield. Among the different methods of applying broadcast urea that we tested, the broadcast application of granular urea onto drained soil shortly after removing floodwater followed by flooding 2 days later appeared to be a good N management practice, offering considerable potential for improving the efficiency of urea applied to lowland rice crops.     

Urea N uptake efficiency of ryegrass (Lolium perenne L.) in the presence of urease inhibitors

Summary A greenhouse experiment was conducted to study the comparative efficiency of urea as an N fertilizer with and without the addition of different urease inhibitors. Ryegrass (Lolium perenne L.) was used as the test plant and the N balance technique with ¹⁵N was applied. Three urease inhibitors, hydroquinone, phenyl phosphorodiamidate (PPDA), and N-(n-butyl) phosphorothioic triamide (NBPT), were evaluated for their effects on urea-N uptake as well as on grass yield. The addition of urease inhibitors, except for hydroquinone in the later growth period, did not significantly influence the dry matter weight. Throughout the whole growth period, only NBPT significantly increased the total urea-N uptake. In the uninhibited system, the major fertilizer N loss occurred during the first period of grass growth, presumably via NH₃ volatilization, since the environment did not favour the other pathways of N loss. However, an appreciable amount of urea N was lost during the later growth period in all inhibited systems, especially in the hydroquinone-treated system. This indicates that the application of urease inhibitors could not eliminate the urea N loss. The greater N loss in the hydroquinone-treated soil appears to be related to the inhibition by hydroquinone of nitrification.