好氧条件下两种水稻土的氮素总转化速率比较

Although to date individual gross N transformations could be quantified by ~(15)N tracing method and models,studies are still limited in paddy soil.An incubation experiment was conducted using topsoil(0-20 cm) and subsoil(20-60 cm) of two paddy soils,alkaline and clay(AC) soil and neutral and silt loam(NSL) soil,to investigate gross N transformation rates.Soil samples were labeled with either ~(15)NH4_NO_3 or NH_4~(15)NO_3,and then incubated at 25 °C for 168 h at 60%water-holding capacity.The gross N mineralization(recalcitrant and labile organic N mineralization) rates in AC soil were 1.6 to 3.3 times higher than that in NSL soil,and the gross N nitrification(autotrophic and heterotrophic nitrification) rates in AC soil were 2.4 to 4.4 times higher than those in NSL soil.Although gross NO_3~- consumption(i.e.,NO_3~- immobilization and dissimilatory NO_3~- reduction to NH_4~+ rates increased with increasing gross nitrification rates,the measured net nitrification rate in AC soil was approximately 2.0 to 5.1 times higher than that in NSL soil.These showed that high NO_3~- production capacity of alkaline paddy soil should be a cause for concern because an accumulation of NO_3~- can increase the risk of NO_3~- loss through leaching and denitrification.     

Nitrapyrin effectiveness in reducing nitrous oxide emissions decreases at low doses of urea in an Andosol

In the tropics,frequent nitrogen(N)fertilization of grazing areas can potentially increase nitrous oxide(N₂O)emissions.The application of nitrification inhibitors has been reported as an effective management practice for potentially reducing N loss from the soil-plant system and improving N use efficiency(NUE).The aim of this study was to determine the effect of the co-application of nitrapyrin(a nitrification inhibitor,NI)and urea in a tropical Andosol on the behavior of N and the emissions of N₂O from autotrophic and heterotrophic nitrification.A greenhouse experiment was performed using a soil(pH 5.9,organic matter content 78 g kg^-1,and N 5.6 g kg^-1)sown with Cynodon nlemfuensis at 60%water-filled pore space to quantify total N₂O emissions,N₂O derived from fertilizer,soil ammonium(NH₄⁺)and nitrate(NO₃^-),and NUE.The study included treatments that received deionized water only(control,NI).No significant differences were observed in soil NH₄⁺content between the UR and UR+NI treatments,probably because of soil mineralization and NO₃^-produced by heterotrophic nitrification,which is not effectively inhibited by nitrapyrin.After 56 d,N₂O emissions in UR(0.51±0.12 mg N₂O-N concluded that the soil organic N mineralization and heterotrophic nitrification are the main processes of NH₄⁺and NO₃^-production.Additionally,it was found that N₂O emissions were partially a consequence of the direct oxidation of the soil's organic N via heterotrophic nitrification coupled to denitrification.Finally,the results suggest that nitrapyrin would likely exert significant mitigation on N₂O emissions only if a substantial N surplus exists in soils with high organic matter content.     

Organic nitrogen stimulates the heterotrophic nitrification rate in an acidic forest soil

Many previous studies have demonstrated that heterotrophic nitrification processes play an important role in the production of NO₃⁻ in acidic soils. However, it is not clear whether a low concentration of nitrogenous organic compounds support heterotrophic nitrification processes in natural soils. In this study, we performed an ¹⁵N tracer experiment with a glycine concentration gradient (20, 40, 80, and 160 mg N kg⁻¹) to investigate the effect of the organic nitrogen concentration on the heterotrophic nitrification rate and its relative contribution to the total nitrification of the studied acidic forest soil. This experiment demonstrated that ¹⁵N–NO₃⁻ accumulated over time with all nitrogen treatments in the presence of acetylene, confirming that heterotrophic nitrification occurred even at a low organic nitrogen concentration (20 mg kg⁻¹) in the studied acidic forest soil. In the presence of acetylene, the ¹⁵N–NO₃⁻ concentration in the 20 and 40 mg kg⁻¹ glycine-N treatments was significantly lower than in the 80 and 160 mg kg⁻¹ glycine-N treatments (p < 0.05), indicating that a high organic nitrogen concentration stimulated the heterotrophic nitrification rate. There was no significant difference in the average contribution of heterotrophic nitrification to total nitrification among the different nitrogen treatments, suggesting that the organic nitrogen concentration did not affect the relative contribution of heterotrophic nitrification to total nitrification in the studied acidic soil. Our results confirmed that a low concentration of organic N (20 mg kg⁻¹) supported heterotrophic nitrification in the studied soil. The organic nitrogen concentration stimulates the heterotrophic nitrification rate, but does not affect the relative contribution of heterotrophic nitrification to total nitrification in the studied acidic soil.     

亚热带松林中强酸性土壤自养和异养硝化作用的研究

The occurrence of nitrification in some acidic forest soils is still a subject of debate. Identification of main nitrification pathways in acidic forest soils is still largely unknown. Acidic yellow soil (Oxisol) samples were selected to test whether nitrification can occur or not in acidic subtropical pine forest ecosystems. Relative contributions of autotrophs and heterotrophs to nitrification were studied by adding selective nitrification inhibitor nitrapyrin. Soil NH₄⁺-N concentrations decreased, but NO₃^--N concentrations increased significantly for the no-nitrapyrin control during the first week of incubation, indicating that nitrification did occur in the acidic subtropical soil. The calculated net nitrification rate was 0.49 mg N kg^-1 d^-1 for the no-nitrapyrin control during the first week of incubation. Nitrapyrin amendment resulted in a significant reduction of NO₃^--N concentration. Autotrophic nitrification rate averaged 0.28 mg N kg^-1 d^-1 and the heterotrophic nitrification rate was 0.21 mg N kg^-1 d^-1 in the first week. Ammonia-oxidizing bacteria (AOB) abundance increased slightly during incubation, but nitrapyrin amendment significantly decreased AOB amoA gene copy numbers by about 80%. However, the ammonia-oxidizing archaea (AOA) abundance showed significant increases only in the last 2 weeks of incubation and it was also decreased by nitrapyrin amendment. Our results indicated that nitrification did occur in the present acidic subtropical pine forest soil, and autotrophic nitrification was the main nitrification pathway. Both AOA and AOB were the active biotic agents responsible for autotrophic nitrification in the acidic subtropical pine forest soil.     

Importance of heterotrophic nitrification and dissimilatory nitrate reduction to ammonium in a cropland soil: Evidences from a 15N tracing study to literature synthesis

Future climate change is predicted to influence soil moisture regime, a key factor regulating soil nitrogen (N) cycling. To elucidate how soil moisture affects gross N transformation in a cultivated black soil, a ¹⁵N tracing study was conducted at 30%, 50% and 70% water-filled pore space (WFPS). While gross mineralization rate of recalcitrant organic N (N_rec) increased from 0.56 to 2.47 mg N kg⁻¹ d⁻¹, the rate of labile organic N mineralization declined from 4.23 to 2.41 mg N kg⁻¹ d⁻¹ with a WFPS increase from 30% to 70%. Similar to total mineralization, no distinct moisture effect was found on total immobilization of ammonium, which primarily entered the N_rec pool. Nitrate (NO₃⁻) was mainly produced via autotrophic nitrification, which was significantly stimulated by increasing WFPS. Unexpectedly, heterotrophic nitrification was observed, with the highest rate of 1.06 mg N kg⁻¹ d⁻¹ at 30% WFPS, contributing 31.8% to total NO₃⁻ production, and decreased with WFPS. Dissimilatory nitrate reduction to ammonium (DNRA) increased from near zero (30% WFPS) to 0.26 mg N kg⁻¹ d⁻¹ (70% WFPS), amounting to 16.7–92.9% of NO₃⁻ consumption. A literature synthetic analysis from global multiple ecosystems showed that the rates of heterotrophic nitrification and DNRA in test soil were comparative to the forest and grassland ecosystems, and that heterotrophic nitrification was positively correlated with precipitation, soil organic carbon (SOC) and C/N, but negatively with pH and bulk density, while DNRA showed positive relationships with precipitation, clay, SOC, C/NO₃⁻ and WFPS. We suggested that low pH and bulk density and high SOC and C/N in test soil might favor heterotrophic nitrification, and that C and NO₃⁻ availability together with anaerobic condition were crucial for DNRA. Overall, our study highlights the role of moisture in regulating gross N turnover and the importance of heterotrophic nitrification for NO₃⁻ production under low moisture and DNRA for NO₃⁻ retention under high moisture in cropland.     

Evidence of carbon stimulated N transformations in grassland soil after slurry application

High nitrification rates which convert ammonium (NH₄⁺) to the mobile ions NO₂⁻ and NO₃⁻ are of high ecological significance because they increase the potential for N losses via leaching and denitrification. Nitrification can be performed by chemoautotrophic or heterotrophic organisms and heterotrophic nitrifiers can oxidise either mineral (NH₄⁺) or organic N. Selective nitrification inhibitors and ¹⁵N tracer studies have been used in an attempt to separate heterotrophic and autotrophic nitrification. In a laboratory study we determined the effect of cattle slurry on the oxidation of mineral NH₄⁺-N and organic-N by labelling the NH₄⁺ or NO₃⁻ pools separately or both together with ¹⁵N. The size and enrichment of the mineral N pools were determined at intervals. To calculate gross N transformation rates a ¹⁵N tracing model was developed. This model consists of the three N-pools NH₄⁺, NO₃⁻ and organic N. Sub-models for decomposition of degradable carbon in the soil and the slurry were added to the model and linked to the N transformation rates. The model was set up in the software ModelMaker which contains non-linear optimization routines to determine model parameters. The application of cattle slurry increased the rate of nitrifcation by a factor of 20 compared with the control. The size and enrichment of the mineral N pools provided evidence that nitrification was due to the conversion of NH₄⁺ to NO₃⁻ and not the conversion of organic N to NO₃⁻. There was evidence that slurry-enhanced oxidation of NH₄⁺ to NO₃⁻ was due to a combination of autotrophic and heterotrophic transformations. Slurry application increased the mineralisation rate by approximately a factor of two compared with the control and the rate of immobilisation of NH₄⁺ by approximately a factor of three.     

Conversion of forest to agricultural land affects the relative contribution of bacteria and fungi to nitrification in humid subtropical soils

Land-use and management practices can affect soil nitrification. However, nitrifying microorganisms responsible for specific nitrification process under different land-use soils remains unknown. Thus, we investigated the relative contribution of bacteria and fungi to specific soil nitrification in different land-use soils (coniferous forest, upland fields planted with corn and rice paddy) in humid subtropical region in China. ¹⁵N dilution technique in combination with selective biomass inhibitors and C₂H₂ inhibition method were used to estimate the relative contribution of bacteria and fungi to heterotrophic nitrification and autotrophic nitrification in the different land-use soils in humid subtropical region. The results showed that autotrophic nitrification was the predominant nitrification process in the two agricultural soils (upland and paddy), while the nitrate production was mainly from heterotrophic nitrification in the acid forest soil. In the upland soils, streptomycin reduced autotrophic nitrification by 94%, whereas cycloheximide had no effect on autotrophic nitrification, indicating that autotrophic nitrification was mainly driven by bacteria. However, the opposite was true in another agricultural soil (paddy), indicating that fungi contributed to the oxidation of NH₄⁺ to NO₃^?. In the acid forest soil, cycloheximide, but not streptomycin, inhibited heterotrophic nitrification, demonstrating that fungi controlled the heterotrophic nitrification. The conversion of forest to agricultural soils resulted in a shift from fungi-dominated heterotrophic nitrification to bacteria- or fungi-dominated autotrophic nitrification. Our results suggest that land-use and management practices, such as the application of N fertilizer and lime, the long-term waterflooding during rice growth, straw return after harvest, and cultivation could markedly influence the relative contribution of bacteria and fungi to specific soil nitrification processes.     

应重视硝态氮同化过程在降低土壤硝酸盐浓度中的作用

在保证生产力条件下,采取合理的氮肥管理措施降低土壤硝态氮浓度对降低氮污染至关重要。当前,应用硝化抑制剂能够有效延缓铵态氮的硝化速率,进而降低土壤硝态氮淋溶损失和氮氧化物排放,但是其缺点显而易见:促进氨挥发并引起硝化抑制剂污染。好氧条件下,土壤硝态氮净变化量取决于产生(硝化)和消耗(硝态氮同化)的量。但是,一直以来,受微生物优先利用铵态氮这一传统观点的影响,人们普遍认为农田土壤微生物较少利用硝态氮,很大程度上忽视了对硝态氮同化过程的研究。该过程独具优势,它将硝态氮转变为微生物生物量氮进行短期储存并发生再矿化,具有保氮功能且环境友好。加入特定的碳源可以提高硝态氮同化这已是不争的事实,未来应加强硝态氮同化降低土壤硝酸盐累积方面的研究:(1)外源碳影响硝态氮同化的微生物驱动机制是什么?(2)怎样才能操控硝态氮同化和再矿化过程,使得作物氮需求和土壤氮供应相匹配,进而降低氮损失?(3)在碳源充足的条件下,反硝化作用亦会增强,如何才能做到在提高硝态氮同化的同时避免反硝化氮损失?     

Effect of tebuthiuron on soil N mineralization and nitrification

Abstract

Herbicides have potential for economical and efficient site preparation following timber harvest. The effects of tebuthiu‐ron, one of the herbicides approved for this use, on soil nitrogen (N) mineralization and nitrification were determined in laboratory incubations. Tebuthiuron was added at rates from 0 to 1000 μg g^‐1 to three soils. There was no effect of tebuthiuron additions of less than 1 μg g^‐1 on soil N mineralization and nitrification. Tebuthiuron reduced nitrification in all soils at 1000 μg g^‐1 and in two of the soils at 100 μg g^‐1 . All soils had increased net mineralization with tebuthiuron added at 100 and 1000 μg g^‐1. The addition of 50 μg NH⁺ ₄‐N and 1000 μg tebuthiuron g^‐1 resulted in increased net mineralization in the three soils. Nitrification was affected differently in each of the three soils by the addition of both NH⁺ ₄‐N and tebuthiuron. The added NH⁺ ₄‐N either removed the inhibition of nitrification by the herbicide or had no effect on the inhibition in two of the soils. In the third soil, nitrification was reduced by the addition of NH⁺ ₄‐N.

The presence of NO^‐ ₃‐N in these acid soils and the effects of added NH⁺ ₄‐N on NO^‐ ₃‐N production suggest that heterotrophic nitrification occurs in at least two of the soils. The findings of this study indicate that any effects of tebuthiuron on N mineralization and nitrification at the currently recommended application rates are likely to be transient and localized.     

烤烟钾素库源关系生理调控措施研究

在大田生产条件下 ,采用单株挂牌设置处理的研究方法 ,研究涂抹生长素与其它不同生长调节剂和烟株顶端调控等措施对烤烟钾吸收及其在库源中再分配的影响。结果表明 ,现蕾后不打顶或打顶结合生长素处理茎断面均有利于不同部位叶片含钾量的提高 ,以打顶结合涂抹生长素效果更好 ;内源生长素和外源生长素都有利于烟株体内的钾素向叶片中分配 ,其中外源生长素的活性更强 ,能更有效地提高烟株叶片的含钾量 ,且涂抹 2次比涂抹 1次的效果好 ,但涂抹次数间差异不显著。     

Heterotrophic nitrification is the predominant NO3 − production pathway in acid coniferous forest soil in subtropical China

To date, occurrence and stimulation of different nitrification pathways in acidic soils remains unclear. Laboratory incubation experiments, using the acetylene inhibition and ¹⁵N tracing methods, were conducted to study the relative importance of heterotrophic and autotrophic nitrification in two acid soils (arable (AR) and coniferous forest) in subtropical China, and to verify the reliability of the ¹⁵N tracing model. The gross rate of autotrophic nitrification was 2.28 mg?kg^?1?day^?1, while that of the heterotrophic nitrification (0.01 mg?kg^?1?day^?1) was negligible in the AR soil. On the contrary, the gross rate of autotrophic nitrification was very low (0.05 mg?kg^?1?day^?1) and the heterotrophic nitrification (0.98 mg?kg^?1?day^?1) was the predominant NO₃ ^? production pathway accounting for more than 95 % of the total nitrification in the coniferous forest soil. Our results showed that the ¹⁵N tracing model was reliable when used to study soil N transformation in acid subtropical soils.     

Effect of reforestation on turnover of 15N-labelled nitrate and ammonium in relation to changes in soil microflora

The effects of incubation time, vegetation type (represented by a pine plantation, a protected and a periodically burnt eucalypt forest), lime and finely ground pine needles on the transformation of (¹⁵NH₄)₂SO₄ and K¹⁵NO₃ were studied in incubation experiments with a sandy lateritic podzolic soil from south-east Queensland. Microorganisms were counted so as to relate N transformations to particular groups of microorganisms.The heterotrophic miroflora utilized NH⁺₄ as a source of N in preference to NO^?₃, and autotrophic nitrifiers seemed to be weak competitors for NH⁺₄. Lime caused a slight loss of NO^?₃ and this was accompanied by an increase in the population of denitrifying bacteria.Lime promoted immobilization of NH⁺₄ by heterotrophic bacteria and subsequent mineralization by nitrifying bacteria, but when pine needles were also added the nitrifiers were suppressed and immobilization by heterotrophic bacteria dominated. Pine needles alone stimulated fungi to immobilize NH⁺₄.While reforestation with exotic pines caused a loss of total-N there was evidence of increased turnover, i.e. more rapid immobilization and nitrification, in pine plantation soils. Prescribed burning also promoted nitrification while reducing total-N.     

Mechanisms behind soil N dynamics following cover restoration in degraded land in subtropical China

Purpose

Nitrogen (N) is an important nutrient for re-vegetation during ecosystem restoration, but the effects of cover restoration on soil N transformations are not fully understood. This study was conducted to investigate N transformations in soils with different cover restoration ages in Eastern China.

Materials and methods

Soil samples were collected from four degraded and subsequently restored lands with restoration ages of 7, 17, 23, and 35 years along with an adjacent control of degraded land. A ¹⁵N tracing technique was used to quantify gross N transformation rates.

Results and discussion

Compared with degraded land, soil organic carbon (SOC) and total N (TN) increased by 1.60–3.97 and 2.49–5.36 times in restoration land. Cover restoration increased ammonium and nitrate immobilization, and dissimilatory nitrate reduction to ammonium (DNRA) by 0.56–0.96, 0.34–2.10, and 0.79–3.45 times, respectively, indicating that restoration was beneficial for N retention. There were positive correlations between SOC content and ammonium and nitrate immobilization and DNRA, indicating that the increase in soil N retention capacity may be ascribed to increasing SOC concentrations. The stimulating effect of SOC on ammonium immobilization was greater than its effect on organic N mineralization, so while SOC and TN increased, inorganic N supply did not increase. Autotrophic and heterotrophic nitrification increased with increasing SOC and TN concentrations. Notably, heterotrophic nitrification was an important source of NO₃^??N production, accounting for 47–67% of NO₃^??N production among all restoration ages.

Conclusions

The capacity of N retention was improved by cover restoration, leading to an increase in soil organic carbon and total N over time, but inorganic N supply capacity did not change with cover restoration age.

     

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.     

Nitrification potential of marsh soils from two natural saline–alkaline wetlands

Few studies have been carried out on nitrification potential of marsh soils in natural saline wetlands with high alkalinity. The nitrification potentials of a closed wetland and an open wetland were monitored by an aerobic incubation at 25°C for 28 days. The relative nitrification index ( RNI,\frac\textNO₃^- \text - NNO₃^- - N + NH₄⁺ - N ) \left( {{\hbox{RNI,}}\frac{{{\text{NO}}_3^{-} {\text{ - N}}}}{{{\hbox{NO}}_3^{-} {\hbox{ - N}} + {\hbox{NH}}_4^{+} {\hbox{ - N}}}}} \right) rapidly increased with time in both wetlands and decreased with depth in soil profiles in both wetlands within the first 21 days. Nitrification proceeded much faster in the closed wetland than in the open wetland. The higher rate of nitrogen removal in closed wetlands than open wetland was probably due to the fast nitrification followed by denitrification or leaching loss.     

Heterotrophic nitrification is the predominant NO<Stack><Subscript>3</Subscript><Superscript>−</Superscript></Stack> production mechanism in coniferous but not broad-leaf acid forest soil in subtropical China

A study was carried out to investigate the potential gross nitrogen (N) transformations in natural secondary coniferous and evergreen broad-leaf forest soils in subtropical China. The simultaneously occurring gross N transformations in soil were quantified by a ¹⁵N tracing study. The results showed that N dynamics were dominated by NH₄⁺ turnover in both soils. The total mineralization (from labile and recalcitrant organic N) in the broad-leaf forest was more than twice the rate in the coniferous forest soil. The total rate of mineral N production (NH₄⁺ + NO₃⁻) from the large recalcitrant organic N pool was similar in the two forest soils. However, appreciable NO₃⁻ production was only observed in the coniferous forest soil due to heterotrophic nitrification (i.e. direct oxidation of organic N to NO₃⁻), whereas nitrification in broad-leaf forest was little (or negligible). Thus, a distinct shift occurred from predominantly NH₄⁺ production in the broad-leaf forest soil to a balanced production of NH₄⁺ and NO₃⁻ in the coniferous forest soil. This may be a mechanism to ensure an adequate supply of available mineral N in the coniferous forest soil and most likely reflects differences in microbial community patterns (possibly saprophytic, fungal, activities in coniferous soils). We show for the first time that the high nitrification rate in these soils may be of heterotrophic rather than autotrophic nature. Furthermore, high NO₃⁻ production was only apparent in the coniferous but not in broad-leaf forest soil. This highlights the association of vegetation type with the size and the activity of the SOM pools that ultimately determines whether only NH₄⁺ or also a high NO₃⁻ turnover is present.     

华北平原农田生态系统土壤C、N净矿化及尿素转化研究

以华北平原区4个农田生态系统[京郊蔬菜大棚(GH)和河北栾城(LF)、河北南皮(NF)、山东惠民(HF)3个粮田]为研究对象,采用室内好气、恒温、避光条件下培养30.d,对比研究了不同海拔和不同农业扰动强度下的农田生态系统中耕层(020.cm)土壤的净N矿化、净硝化、净C矿化以及尿素的转化,旨在探索人类农业扰动强度和地理海拔对土壤供N潜力和尿素N转化的影响。结果表明,4个地区的土壤供N潜力分别为:14.4、13.2,17.7和16.5.mg/kg,说明高度熟化的华北区农田土壤供N潜力相对稳定。以施用有机肥为主的蔬菜大棚和以施用化肥为主的粮田对土壤供N没有显著影响。农田土壤净矿化后的供N形式主要是NO3--N。以施用有机肥为主的蔬菜大棚积累了较高的土壤有机质和全N,但是土壤净C矿化以及施用尿素后CO2的排放量均低于以施用化肥为主的粮田。尿素在各区域农田土壤中水解转化后均主要以NO3--N形式存在,NO3--N占尿素水解后无机N增量的98%9～9%;华北平原农田生态系统施入尿素态N.30d后,水解成有效态无机N的转化率为63.4%8～3.2%,即每克尿素态N在京郊蔬菜大棚(GH)、栾城高产农田(LF)、南皮农田(NF)和惠民农田(HF)土壤中转化为NO3--N的量分别为0.69、0.82、0.64和0.63.g/kg,同时可使相应区域农田的CO2排放量分别增加CO21.20、1.360、.67和1.58.g/kg。     

Evaluation of nitrification inhibitors for use under tropical conditions

Abstract

Six simple chemical compounds were evaluated for inhibition of nitrification. The compounds of o‐nitroaniline, m‐nitroaniline, o‐nitrophenol, benzotriazole, and 2,4,6‐trinitrophenol were compared with dicyandiamide by adding 10 μg inhibitor/g of a sandy loam soil, incubating for 30 days at 30°C and analyzing for NH⁺ ₄, NO^‐ ₂, and NO^‐ ₃ formation. The results indicated that benzotriazole, o‐nitrophenol, and m‐nitroaniline were very effective nitrification inhibitors.     

生物硝化抑制剂——一种控制农田氮素流失的新策略

农业生产中氮肥的施用是影响全球氮素循环的一个重要因素,在促进作物增产的同时,也对生态环境产生了重要的影响。由于铵态氮肥在旱地中很容易经过硝化作用转变为硝态氮,其中一小部分为植物所吸收,而大量的硝态氮被淋失,或经反硝化作用进入大气,造成土壤氮素严重损失。自然界中一些植物的根系能够分泌抑制硝化作用的物质,被称为生物硝化抑制剂,因而可以显著提高土壤氮素利用率。本文阐述了有关生物硝化抑制剂的由来、分泌调节、作用机制及其应用潜力,并探讨了其在农业生产中氮素高效管理等方面的应用前景。     

Low soil C:N ratio results in accumulation and leaching of nitrite and nitrate in agricultural soils under heavy rainfall

Nitrate (NO^-₃) and nitrite (NO₂^-) leaching threatens groundwater quality.Soil C:N ratio,i.e.,the ratio of soil organic carbon to total nitrogen,affects mineralization,nitrification,and denitrification;however,its mechanism for driving soil NO^-₃ and NO^-₂ accumulation and leaching remains unclear.Here,a field investigation in a fluvo-aquic soil and a soil column experiment were performed to explore the relation...