Influence of temperature on mineralization kinetics with a nitrification inhibitor (mixture of dicyandiamide and ammonium thiosulphate)

Summary The influence of temperature on the action of a dicyandiamide nitrification inhibitor was studied during a laboratory incubation after the addition of ammonium sulphate labelled with ¹⁵N. In the control treatment, nitrification was only slightly affected by temperature and was rapid; on the 42nd day, two-thirds of the ¹⁵N was incorporated into the nitrate fraction while no further tracer was found in ammoniacal form. With the addition of dicyandiamide, the process was slowed down considerably when the temperature was maintained at 10°C, and only about 10% of the ¹⁵N was nitrified in 6 months. After 1 month of incubation at 10°C, a temperature increase to 15°C for 4 weeks modified the nitrification kinetics only slightly. However, as soon as the temperature reached 20°C, the beginning of dicyandiamide decomposition and an increase in the quantity of NO ₃ ^- -N was observed. The inhibition was measured by the nitrification index, which was greater than 80% as long as the temperature did not exceed 15°C, and decreased to 10% after 6 months; this value was reached only after 1 year in soil maintained at 10°C. The half-life of the NH ₄ ⁺ was decreased by raising the temperature. In the experimental conditions described, nitrification was inhibited by the dicyandiamide for at least 6 months provided the temperature did not exceed 15°C.     

Estimation of simultaneous nitrification and denitrification in grassland soil associated with urea-N using 15N and nitrification inhibitor

 A low efficiency of use of N fertilisers has been observed in mid-Wales on permanent pasture grazed intensively by cattle. Earlier laboratories studies have suggested that heterogeneity in redox conditions at shallow soil depths may allow nitrification and denitrification to occur concurrently resulting in gaseous losses of N from both NH₄ ⁺ and NO₃ ^–. The objective of the investigation was to test the hypothesis that both nitrification and denitrification can occur simultaneously under simulated field capacity conditions (∼5 kPa matric potential). Intact soil cores were taken from grassland subjected to both grazing and amenity use. The fate of applied NH₄ ⁺ was examined during incubation. ¹⁵N was used as a tracer. Nitrapyrin was used as a nitrification inhibitor and acetylene was used to block N₂O reductase. More than 50% of N applied as NH₄ ⁺ disappeared over a period of 42 days from the soil mineral-N pool. Some of this N was evolved as N₂O. Accumulation of NO₃ ^––N in the surface 0–2.5 cm indicated active nitrification. Addition of nitrapyrin increased N recovery by 26% and inhibited both the accumulation of NO₃–N and emission of N₂O. When intact field cores were incubated after addition of ¹⁵N-urea, all of the N₂O evolved was derived from added urea-N. It was concluded that nitrification and denitrification do occur simultaneously in the top 7.5 cm or so, of the silty clay loam grassland topsoils of mid-Wales at moisture contents typical of field capacity. The quantitative importance of these concurrent processes to N loss from grassland systems has not yet been assessed. Received: 15 December 1998     

采用15N同位素稀释法研究不同层次土壤氮素总转化速率

采用15N同位素稀释方法,开展短期(7天)室内培养实验,估算了一水稻土0~20、20~60和60~90 cm土层土壤主要N素转化过程的总转化速率,结果表明,标记N溶液加入后2 h内各土层土壤的总矿化、硝化、固定速率显著高于其他时间段(p<0.01)。2 h后,矿化速率在小范围内起伏。0~20 cm土层土壤N素的硝化速率随培养时间延长而降低,另外两层土壤则基本保持稳定,硝化速率的变化与硝化作用底物NH4+-N浓度的变化呈显著正相关。值得注意的是,外源无机N溶液加入后2 h内,大量NH4+-N和NO3--N被固定,并认为N素的非生物固定起主导作用。2 h后,出现了N素在固定与再矿化间反复转换的现象。实验结果表明,与净转化速率相比总转化速率能更好地描述单个N素转化过程,但由于外源N加入对N素转化的影响、再矿化作用以及忽略了N素转化过程中的气体损失、DNRA(硝态氮异化还原为铵)过程等,本研究结果与真实值间存在一定差异。     

Influence of nitrification inhibitors on nitrification and nitrous oxide (N2O) emission from a clay loam soil fertilized with urea

Laboratory incubation experiments were conducted to compare the effects of the nitrification inhibitors 3,4-dimethylpyrazole phosphate (DMPP) and 2-Chloro-6-(trichloromethyl)-pyridine (N-serve) on nitrification and nitrous oxide (N₂O) emission from a Vertosol from southern Australia, under controlled moisture and temperature. Nitrification rates in the control soil were strongly influenced by the temperature and moisture, increasing by a factor of 3.6 for each 10 °C increase between 5 and 25 °C. DMPP inhibited nitrification effectively for 42 days at 5-15 °C and 40-60% water filled pore space (WFPS). DMPP also slowed nitrification appreciably at 25 °C when the soil was at 40% WFPS, but was less effective at 60% water filled pore space. N-serve inhibited nitrification effectively for 42 days under all test conditions. Emissions of N₂O from the urea treatment (no inhibitors) significantly increased with increasing temperature and moisture. The ratio of total N₂O emission to total nitrification was not constant and varied from around 0.03% at 5 °C and 40% WFPS to 0.12% at 25 °C and 60% WFPS. DMPP and N-serve reduced cumulative N₂O emission over 42 days by more than 65% under all the imposed conditions.     

Effects of concentration,incubation temperature,and repeated applications on degradation kinetics of dicyandiamide (DCD) in model experiments with a silt loam soil

Summary The kinetics of dicyandiamide (DCD) decomposition were studied (at 80% water-holding capacity) in pretreated and non-pretreated soils, using model experiments. DCD was added in different concentrations (6.7, 16.7, and 33.3 g DCD-N g^–1 dry soil) and incubated at various temperatures (10°, 20°, and 30°C). Additionally, DCD decomposition was examined in sterile soil (with or without Fe₂O₃) after inoculation with a DCD-enrichment culture. In the sterile variant, (30°C)the applied dicyandiamide concentration remained constant, even after 36 days. In the sterilized and reinoculated variant, DCD disappeared within 7 days. Addition of Fe₂O₃ powder to the sterilized soil had no effect on DCD degradation. In the pretreated soils, DCD mineralization started immediately at all temperatures and concentrations without a lag phase. A temperature increase of 10°C doubled the mineralization rate. The mineralization rates were independent of the initial concentrations. In the non-pretreated soils (except at 30°C with 16.7 and 33.3 g DCD-N g^–1 dry soil) DCD decreased only after a short (30°C) or a long (10°C) lag phase. These results suggest that an inducible metabolic degradation occurred, following zeroorder kinetics.     

Effects of trampling of a wet dairy pasture soil on soil porosity and on mitigation of nitrous oxide emissions by a nitrification inhibitor,dicyandiamide

Urine patches in dairy pastures are major sources of nitrous oxide (N₂O). Wet winters result in compaction damage to pastures because of animal trampling. The nitrification inhibitor, dicyandiamide (DCD), is effective at reducing N₂O emissions from urine patches. Here, we assessed the extent of damage to the physical quality of the soil by trampling and whether this influenced the ability of DCD to mitigate N₂O emissions. A field experiment was conducted where a sandy loam soil was trampled by a mechanical hoof just before urine and DCD application. Trampling reduced air permeability and pore continuity, but this had no effect on bulk density. Urine appeared to have contributed to pore collapse and blockage. Trampling increased average cumulative N₂O emissions from 1.74 to 4.66% of urine‐N applied. This effect was attributed to increased water‐filled pore space, aggregate destruction and suppression of grass growth. DCD was highly effective in reducing N₂O emissions, with the N₂O emission factor of the urine‐N being decreased by 58–63%. Trampling did not significantly affect the effectiveness of DCD in reducing N₂O emissions.     

pH 升高对红壤硝化过程产生 N2O 的影响

对红壤添加NaOH培养获得不同pH系列的土壤.通过室内培养试验.研究了3种pH条件下土壤的N_2O排放和无机N的变化情况.结果表明:硝化活性随土壤pH升高而增强:pH升高增加了土壤N_2O的释放;纯化学过程对N_2O散发的贡献随pH的升高而降低;Nitrapyrin在pH 4.8和pH 6.0时表现山硝化抑制作用,在pH 8.5时抑制效果不明显,且提高了培养期间pH8.5土壤N_2O的释放量.     

Anthracene influence on (15NH4)2SO4 fertilization of wheat seedlings

The influence of the addition of anthracene (1 μg anthracene g^?1 soil) in N transformations following (¹⁵NH₄)₂SO₄ fertilization (200 mg N g^?1 soil) was investigated in wheat pots by quadrapole mass-spectrometry. The dry matter yield at harvesting (after 16 days) was not statistically affected (P=0.05) by anthracene addition. The total amount of N from the fertilizer taken up by wheat seedings in 16 days was 29 and 26.8% of the added N in the absence and in the presence of anthracene, respectively, but the difference was not significantly different at level P=0.05. In order to investigate more deeply the effect of anthracene on the N cycle in the soil-plant system, the first-order rate constants of N mineralization, N immobilization, nitrification and N plant uptake have been determined according to a ¹⁵N + ¹⁴N soil-plant model. The comparison of the constants showed that organic N mineralization, nitrification and plant uptake proceeded at the same rate, while a small different rate (P=0.05) was shown by N immobilization. In fact, the N immobilization constant increased from 0.14±0.012 to 0.21±0.014 day^?1 as a consequence of anthracene addition.     

Impact of urease and nitrification inhibitor on NH4+ and NO3− dynamic in soil after urea spring application under field conditions evaluated by soil extraction and soil solution sampling

The application of mineral nitrogen (N) fertilizers is one of the most important management tools to ensure and increase yield in agricultural systems. However, N fertilization can lead to various ecological problems such as nitrate () leaching or ammonia and nitrous oxide emissions. The application of N stabilizers (i.e., inhibitors) combined with urea fertilization offers an effective option to reduce or even prevent N losses due to their regulatory effect on ammonium () and release into the soil. The present field experiment therefore aimed at soil N speciation dynamics after urea spring fertilization (225 kg N ha^?1) in the presence of a urease inhibitor (UI), a nitrification inhibitor (NI), both inhibitors (UI+NI) or when no inhibitor was applied at all. The study focused on the distribution of N species among soil matrix and soil solution. Plant cultivation was completely omitted in order to avoid masking soil N turnover and speciation by plant N uptake and growth dynamics. Application of UI clearly delayed urea hydrolysis in the top soil, but a complete hydrolysis of urea took place within only 10 days after fertilization (DAF). Nitrification was significantly reduced by NI application, leading to higher and lower concentrations in treatments with NI. Due to sorption of to the soil matrix a significantly larger fraction of was always detected in the soil extracts compared to soil solution. However, while in soil extracts the impact of NI application was less apparent and delayed, in soil solution a quick response to NI application was observed as revealed by significantly increased soil solution concentrations of . Because of the “asymmetric” soil phase distribution soil solution was predominant over only initially after fertilization even in inhibitor treatments (≈ 8 to 10 DAF). Nevertheless, inhibitor application tended towards closer ratios of to concentration in soil solution and hence, might additionally affect concentration dependent processes like plant N uptake and root development. Despite cold spring conditions urea application along with UI and/or NI did not indicate a limited supply of plant available and .     

三种硝化抑制剂在石灰性土壤中的应用效果比较

在人工气候室内采用25℃黑暗培养法研究双氰胺(DCD)、3,4-二甲基吡唑磷酸(DMPP)及2-氯-6-三氯甲基吡啶(Nitrapyrin)在石灰性土壤中的硝化抑制效果。结果表明:施用DCD、DMPP、Nitrapyrin的土壤NH4+-N含量较单施硫酸铵的土壤(对照)分别提高228.45~244.85 mg/kg(砂土)、209.75~254.79 mg/kg(黏土),NO3--N含量较对照分别降低93.85%~94.99%(砂土)、91.82%~95.38%(黏土)。表观硝化率随培养进程增加缓慢,培养期间只增加了1.28%~2.09%(砂土)、2.72%~8.40%(黏土),而对照增加了86.00%(砂土)、80.89%(黏土)。3种硝化抑制剂均显著抑制了石灰性土壤中硫酸铵水解铵硝化作用的进行,并且在砂土中的硝化抑制率高于黏土,硝化抑制效果最好的为DMPP处理,0.54%Nitrapyrin处理次之但用量最小,0.27%Nitrapyrin和10.8%DCD处理抑制效果相对较弱。     

Effects of the nitrification inhibitor dicyandiamide on soil mineral N, pasture yield, nutrient uptake and pasture quality in a grazed pasture system

Recent lysimeter studies have demonstrated that the nitrification inhibitor, dicyandiamide (DCD), can reduce nitrate (NO) leaching losses from cow urine patches in grazed pasture systems. The objective of this study was to quantify the effects of fine particle suspension (FPS) DCD on soil mineral N components, pasture yield, nutrient uptake and pasture quality under grazed pasture conditions. A field study was conducted on the Lincoln University dairy farm, Canterbury, New Zealand, from 2002 to 2006. FPS DCD was applied to grazed pasture plots at 10 kg ha^?1 in early May in addition to applied cow urine patches at a nitrogen (N) loading rate of 1000 kg N ha^?1, with DCD reapplied in early August. Soil mineral N levels in the urine patches were monitored. Pasture yield, N and cation concentrations and uptake were measured in treatment urine patches and inter‐urine areas of the pasture. Comparisons were made with control plots which did not receive DCD. NO levels under the DCD‐treated urine patches (0–7.5 cm) were in the order of 10 kg N ha^?1 compared with 40–80 kg N ha^?1 under untreated patches, and soil ammonium (NH) levels were consistently higher under the DCD‐treated patches. The DCD significantly and consistently increased pasture yield in both the urine patches, and inter‐urine areas of the pasture in all 4 years of the trial. Mean annual dry matter (DM) yields over 4 years were inter‐urine areas, 10.3; inter‐urine + DCD, 12.4; urine, 12.4 and urine +DCD 16.0 t DM ha^?1, representing an average DM yield increase of 20 and 29% in inter‐urine and urine patch areas, respectively. On a whole paddock basis, the increase in annual DM yield resulting from DCD application was estimated to be 21%. N, calcium (Ca), magnesium (Mg) and potassium (K) concentrations in pasture were unaffected by treatment with DCD; however, total annual uptake of these nutrients by pasture was significantly higher in all years where DCD had been applied. Pasture DM, protein, carbohydrate, metabolizable energy and fibre levels and sward clover content were not affected by treatment with DCD. The results demonstrate the agronomic value of the DCD treatment in addition to the environmental benefits in a grazed pasture system.     

Nitrogen cycling in two Norway spruce (Picea abies) ecosystems and effects of a (NH4)2SO4 addition

Nitrogen cycling in two Norway spruce (Picea abies (L.) Karst.) ecosystems in the ARINUS experimental watershed areas Schluchsee and Villingen (Black Forest, SW Germany) and initial effects of a (NH₄)₂SO₄ treatment are discussed. Although N reserves in the soils are similar and atmospheric N input is the same low to moderate level characteristic for many forested areas in SW Germany, N export by both seepage and streamwater differs considerably. At Villingen, deposited N is almost totally retained in the ecosystem, whereas at Schluchsee N export is the order of the input. This is explained by differences in forest management history. The Villingen site had been subject to excessive biomass export (e.g., litter raking) leading to unfavorable microbial transformations in the soil. In contrast, as a ‘relic’ of the former beech stand, the Schluchsee site is characterized by high biological activity in the soil with vigorous nitrification despite low pH values. Accordingly, the two ecosystems responded differently to the additional N input (150 kg NH₄ ⁺ -N ha^?1 as (NH₄)₂SO₄). Nitrification starting immediately in the Schluchsee soils led to continued Al mobilization and leaching of basic cations and NO₃ ^?. The availability of Mg, already deficient before treatment, further decreased due to Mg leaching and marked N uptake by the stand. In contrast, most of the added N in Villingen was immobilized in the soil. Hence, uptake by the stand and leaching of NO₃ ^? and cations was correspondingly lower than at Schluchsee. The results emphasize the problems associated with the definition of generally applicable values for ‘critical loads’ of N deposition.     

不同肥力农田和不同林型林地红壤总硝化特征研究

在3种不同肥力的农田和3种不同林型林地红壤上利用原状土心-15N库稀释技术原位测定了其总硝化率。结果表明:不同肥力农田和不同林地红壤的总硝化速率在N7.29～23.50μg/(g·d)间波动,总体来说,农田土壤的总硝化速率大于林地土壤。在不同肥力的农田间,施肥处理的总硝化率显著高于不施肥处理(p<0.05)。在不同植被类型林地间,湿地松林地的总硝化率比木荷和混交林林地分别提高了24.8%和66.9%。总硝化包括净硝化和NO3--N的消耗部分。本试验农田NO3--N的消耗速率比林地大,与总硝化率的变化趋势类似。在同一利用方式的不同处理中,NO3--N含量的变化趋势与总硝化速率的变化趋势相类似。     

施氮及添加硝化抑制剂对苜蓿草地N2O排放的影响

为探究旱作紫花苜蓿(MedicagosativaL.)栽培草地氧化亚氮(N_2O)排放对施氮水平及添加硝化抑制剂的响应特征,采用传统静态箱法研究了不同施氮水平[0kg(N)·hm~(-2)(N0)、 50kg(N)·hm~(-2)(N50)、 100kg(N)·hm~(-2)(N100)和150kg(N)·hm~(-2)(N150)]以及添加硝化抑制剂双氰胺(DCD)150kg(N)·hm~(-2)(N150+DCD)对陇东苜蓿草地N_2O排放特征的影响。结果显示,监测期内N0、N50、N100和N150处理N_2O平均排放速率分别为3.5μg·m~(-2)·h~(-1)、4.1μg·m~(-2)·h~(-1)、5.0μg·m~(-2)·h~(-1)和6.1μg·m~(-2)·h~(-1),随着施氮梯度的增加, N_2O排放速率呈增加趋势。添加硝化抑制剂DCD对N_2O排放产生明显的抑制作用。与N150处理相比, N150+DCD处理下苜蓿草地N_2O平均排放速率下降50.7%, N_2O累计排放量显著降低61.6%(P0.05)。施氮对苜蓿产量没有显著影响,而N0、N50、N100和N150处理下单位苜蓿产量N_2O排放量随氮肥梯度的增加而增加,各处理分别为6.5 mg·kg~(-1)、7.8 mg·kg~(-1)、11.3 mg·kg~(-1)和12.5 mg·kg~(-1)。N_2O排放受土壤含水量影响深刻,生长季N_2O排放通量与土壤水分呈显著正相关关系(P0.05),而与土壤温度无显著相关性(P0.05)。综上,旱作紫花苜蓿栽培草地N_2O排放通量随施氮水平的增加明显增加,在相同施氮水平下添加硝化抑制剂DCD能显著抑制N_2O排放。相关研究结果对于该区域苜蓿草地合理施肥以及N_2O减排具有一定的实践指导意义。     

Evaluation of 3,4-dimethylpyrazole phosphate as a nitrification inhibitor in a <Emphasis Type="Italic">Citrus</Emphasis>-cultivated soil

 The objectives of this work were to evaluate the inhibitory action on nitrification of 3,4-dimethylpyrazole phosphate (DMPP) added to ammonium sulphate nitrate [(NH₄)₂SO₄ plus NH₄NO₃; ASN] in a Citrus-cultivated soil, and to study its effect on N uptake. In a greenhouse experiment, 2 g N as ASN either with or without 0.015 g DMPP (1% DMPP relative to NH₄ ⁺-N) was applied 6 times at 20-day intervals to plants grown in 14-l pots filled with soil. Addition of DMPP to ASN resulted in higher levels of NH₄ ⁺-N and lower levels of NO₃ ^–-N in the soil during the whole experimental period. The NO₃ ^–-N concentration in drainage water was lower in the ASN plus DMPP (ASN+DMPP)-treated pots. Also, DMPP supplementation resulted in greater uptake of the fertilizer-N by citrus plants. In another experiment, 100 g N as ASN, either with or without 0.75 g DMPP (1% DMPP relative to NH₄ ⁺-N) was applied to 6-year-old citrus plants grown individually outdoors in containers. Concentrations of NH₄ ⁺-N and NO₃ ^–-N at different soil depths and N distribution in the soil profile after consecutive flood irrigations were monitored. In the ASN-amended soil, nitrification was faster, whereas the addition of the inhibitor led to the maintenance of relatively high levels of NH₄ ⁺-N and NO₃ ^–-N in soil for longer than when ASN was added alone. At the end of the experiment (120 days) 68.5% and 53.1% of the applied N was leached below 0.60 m in the ASN and ASN+DMPP treatments, respectively. Also, leaf N levels were higher in plants fertilized with ASN+DMPP. Collectively, these results indicate that the DMPP nitrification inhibitor improved N fertilizer efficiency and reduced NO₃ ^– leaching losses by retaining the applied N in the ammoniacal form. Received: 31 May 1999     

Effectiveness of dicyandiamide as a nitrification inhibitor in biochar-amended soil

Overuse of nitrogen (N) fertilizers may lead to many environmental issues via N leaching into groundwater and agricultural runoff into surface water. Biochar, a sustainable soil amendment agent, has been widely studied because of its potential to retain moisture and nutrients. However, recent studies have shown that biochar has a very limited ability to improve the retention of negatively charged nitrite (NO₂^-) or nitrate (NO₃^-). Although positively charged ammonium (NH₄⁺) can be better held by biochar, it is usually susceptible to nitrification and can be easily transformed into highly mobile NO₂^-and/or NO₃^-. In practice, dicyandiamide (DCD) has been used to inhibit nitrification, preserving N in its relatively immobile form as NH₄⁺. Therefore, it is likely that the effects of DCD and biochar in soils would be synergistic. In this study, the influences of biochar on the effectiveness of DCD as a nitrification inhibitor in a biochar-amended soil were investigated by combining the experimental results of incubation, adsorption isotherm, and column transport with the simulated results of different mathematical models. Biochar was found to stimulate the degradation of DCD, as the maximum degradation rate slightly increased from 1.237 to 1.276 mg kg^-1 d^-1 but the half-saturation coefficient significantly increased from 5.766 to 9.834 mg kg^-1. Considering the fact that the availability of DCD for nitrification inhibition was continuously decreasing because of its degradation, a novel model assuming non-competitive inhibition was developed to simulate nitrification in the presence of a decreasing amount of DCD. Depending on the environmental conditions, if the degradation of DCD and NH₄⁺ in biochar-amended soil is not significant, improved contact due to the mitigated spatial separation between NH₄⁺ and DCD could possibly enhance the effectiveness of DCD.     

菜地氮肥用量与N2O排放的关系及硝化抑制剂效果

通过连续种植四季蔬菜近一年的大田试验,探究高施氮水平和低氮肥利用率的蔬菜生产系统中,N2O排放量与氮肥施用量之间的定量关系及其机理,并研究硝化抑制剂减少菜地N2O排放的效果.结果表明,在氮肥施用水平为N 0～1 733 kg hm-2a-1间,无论氮肥中是否添加硝化抑制剂,N2O总排放量与氮肥施用量均呈指数函数关系,即氮肥施用量高时,N2O排放率也高.在各氮肥水平处理下,硝化抑制剂均能降低N2O排放,抑制率为8.75％ ～ 25.28％,且这种减排效果随着施氮量增加而增加.在氮肥施用量为N 300或400 kg hm-2季-1时,施用硝化抑制剂减少N2O排放所带来的效益略高于其成本,因此,即使不考虑氮肥利用率的提高等因素,施用硝化抑制剂仍是一种有利的选择.     

Effect of organic matter and urease inhibitors on urea hydrolysis and immobilization of urea nitrogen in an alkaline soil

Summary Laboratory incubation experiments with ¹⁵N-labelled urea were conducted on a Aquic Udifluvent Belgian soil amended with barley straw, in, order to study the influence of three urease inhibitors, hydroquinone, phenyl phosphorodiamidate and N-(n-butyl) phosphorothioic triamide on urea hydrolysis and N transformations. The results demonstrated that the urea was hydrolyzed more rapidly when the soil was amended with ground barley straw. A pronounced inhibition of urease inhibitors occurred with the urea hydrolysis, but it was decreased by increasing the soil organic C content. A severe N immobilization (about 82–100% of the applied urea) occurred in soil samples that were rich in organic C. The addition of urease inhibitors increased urea-N immobilization by 5–30%. N-(n-butyl) phosphorothioic triamide had a stronger effect than the other two inhibitors when they were applied at the rate of 1%. However, the inhibitors decreased N immobilization when the soil was amended with barley straw.