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1.
Ammonium (NH4+) is an important nitrogen (N) source for plant growth. Nevertheless, NH4+–N can be oxidized to nitrate (NO3?) by nitrification and then nitrate and nitrite can be leached into groundwater. The aims of this study were to investigate the effect of the water bicarbonate concentration, pH, and the presence, or not, of a nitrification inhibitor, on the nitrification process. Six treatments were established, changing the pH and the bicarbonate concentration, with or without the nitrification inhibitor. The results showed that an active nitrification process occurred in treatments with high pHs (8 and 7) and with no nitrification inhibitors. This causes an increase in the nitrate and nitrite concentration in the substrate. The use of N–NH4+ fertilizers joint to a nitrification inhibitor, especially in nutritive solutions with a high concentration of bicarbonate and a pH of 8 and 7, decreases nitrate and nitrite accumulation in substrate which can prevent nitrate and nitrite leaching.  相似文献   

2.
Abstract

A disagreement exists in the literature regarding the effect of organic matter on nitrification. Therefore, this investigation was conducted to study the effect of fulvic (FA) and humic acids (HA) on nitrification by chemical means. In part I, results of an experiment showed a general trend for nitrite production to increase with increase application of FA and HA. On the other hand, nitrate production decreased in the presence of FA and HA. Since the previous experiment was conducted in vitro without soil, a second experiment was initiated as discussed below to include the use of a Cecil and Davidson soil. Soil samples mixed with 0 to 1000 mg HA/kg were incubated for 21 days according to the Schmidt and Belser's nitrifying potential procedure, and an alternate method. Ammonium sulfate was added as the N‐source. The soils were then extracted with 2M KC1 for analysis of initial and final nitrate concentrations with which the nitrifying potential was calculated. An additional experiment was included to study nitrification in the presence of plant growth. For this purpose corn plants were grown for 25 days in pots, receiving 0 to 1000 mg HA/kg, 100 mg (NH4)2SO2/kg, and 1 ml of a mixed nitrifier extract. The soils were again extracted with 2M KCl for analysis of initial and final nitrate concentrations and the nitrifying potential. The Schmidt and Belser method yielded results indicating that the Cecil soil had a greater nitrifying potential than the Davidson soil. A tendency was noted in the Davidson soil for nitrification to decrease with added HA. The inhibitory effect of HA on nitrate production was clearly demonstrated by the alternate method, which yielded a linear decrease in nitrate concentrations with increased HA treatments. Plant growth, and humic acid treatments appeared to decrease the final nitrate concentrations in the third experiments. The effect was more pronounced in the Cecil than in the Davidson soil. The nitrifying potential of the Cecil soil under corn, ranging from 1.05 to 2.23 mg NO‐ 3‐N/kg, was three to eight times smaller than that detected in the experiments without plants. These observations are in support of results discussed in Part I.  相似文献   

3.
The activity of a purified urease, obtained from Bacillus pasteurii, was inhibited by humic and fulvic acids obtained from an agricultural soil. Enzyme kinetic studies showed that the humic substances affected the affinity of the enzyme for its substrate (Km) and the maximum velocity of the reaction (Vmax). The Vmax was inhibited to the same extent by both humic (HA) and fulvic (FA) acids, the precise effect depending on the pH and concentration of humic substance. At pH 4.0, HA concentrations of 25 pg cm?3 and 10 μg cm?3 inhibited the Vmax by 38.5% and 20% respectively. HA and FA had similar effects on the Km but in this case the lowering of the affinity of the enzyme for its substrate was not concentration dependent in the range 0–25 μg cm?3 of humic substance. Typically, the affinity was decreased from a KM of 50 mM in the control to 67 mM in the presence of HA and FA. The effects were not due primarily to the ash or N contents of the humic substances because de-ashed humic acid and synthetic model humic (made from catechol, guaiacol, pyrogallol, resorcinol and protocatechuic acid) and fulvic acid (made from polymaleic acid), containing virtually no ash or N, were equally as effective. The effect was not related to the phenolic monomers which, before polymerization, had no effect on urease activity.  相似文献   

4.
Abstract

An investigation was conducted to study the effect of humic (HA) and fulvic acid (FA) on the dissolution of aluminum phosphate (AlPO4) and iron phosphate (FePO4), to analyze the dissolution products, and assess their availability to plants. The rate of dissolution was determined by shaking 10 mg of Al‐ or FePO4 with 0 to 800 mg L‐1 of HA or FA solutions at pH 7.0 for 0 to 192 hours. The phosphorus (P) concentration was measured in the extracts by spectrophotometry, whereas the nature of P‐humic acid complexes was determined by 31P NMR analysis. Availability of dissolution products was studied by growing corn plants in aerated hydroponic solutions receiving treatments of 50 mg Al‐ or FePO4 and 0 to 800 mg L‐1 of HA or FA at pH 5.0. The results indicated that the amount of P released by HA or FA increased with time. Humic acid was more effective than FA in dissolving the metal phosphates. The 31P NMR analysis showed that the dissolution products contained free orthophosphates and minor amounts of P‐humic acid complexes. This confirms the role of HA as a powerful chelator of Al and Fe, liberating in this way the orthophosphate anions. Corn plants grown in hydroponics, with AlPO4 or FePO4 as the source of P, exhibited better growth performance when HA or FA are present.  相似文献   

5.
Abstract

The effectiveness of Stay‐N 2000 or reformulated nitrapyrin [2‐chloro‐6‐(tricholoromethyl) pyridine] was investigated in two Iowa soils representative of Clarion and Okoboji soils that differed in organic carbon, pH, and texture. A nonlinear regression was used to estimate kinetic parameters. The maximum nitrification rate (K max) and the duration of lag period (t′) were derived from the equation to characterize the nitrification process in both soils. Stay‐N 2000 appeared to be a better inhibitor than nitrapyrin to extend t′ and as effective as nitrapyrin in reducing K max. Stay‐N 2000 reduced K max an appreciable amount in the Okoboji soil at the rate of 12 µg a.i. g?1 soil or three times the recommended rate. Nitrification rates were affected by the rates of nitrogen (N) applied to both soils; the higher the N rates, the higher Kmax, and the more the nitrate (NO3 ?)‐N accumulation.  相似文献   

6.
Abstract

Heavy‐metal inhibition of nitrification in soils treated with reformulated nitrapyrin was investigated. Clarion and Okoboji soils were treated with ammonium sulfate [(NH4)2SO4] and a nitrification inhibitor. Copper(II) (Cu), Zinc(II) (Zn), Cadmium(II) (Cd), or Lead(II) (Pb) were added to each soil. A first‐order equation was used to calculate the maximum nitrification rate (K max), duration of lag period (t′), period of maximum nitrification (Δt), and the termination period of nitrification (t s). In the Clarion soil, the K max decreased from 12 mg kg?1 d?1 without the nitrification inhibitor to 4, 0.25, 0.86, and 0.27 mg kg?1 d?1, respectively, when the inhibitor and Cu, Zn, Pb, or Cd were applied. In the Okoboji soil, K max decreased from 22 mg kg?1 d?1 with no inhibitor to 6, 3, 4, and 2 mg kg?1 d?1, respectively, when an inhibitor and Cu, Zn, Pb, or Cd were added. The t′ varied from 8 to 25 d in the Clarion soil and from 5 to 25 d in the Okoboji soil, due to addition of Cu, Zn, Pb, or Cd and the inhibitor.  相似文献   

7.
Abstract

Nitrification in soil is characterized by a sigmoidal curve with a delay, maximum rate and retarded phase. A model based on the Verhulst equation describes all three phases of the nitrification process excellent. Equations to calculate the maximum nitrification rate (Kmx) and the delay period (t') exist already. Equations to calculate the approximate duration (?t) and termination (ts) of the maximal rate phase were also derived from the Verhulst equation and are reported. The duration of maximal nitrification when NH4 + is oxidized at a maximal rate is the period from the end of the delay period until the retarded phase starts. The termination of the maximal rate phase gives an approximate time of when the retarded phase, due to a depletion of HH4 +, starts. At this stage in the nitrification process additional NH4 + must be applied to prevent the minimum changes in the maximum nitrification rate of a soil. When first‐order kinetics is used, the course of nitrification can in future consequently be described quantitatively by four parameters Kmx, t’, ?t and ts. Similar parameters can also be calculated from experimental data of other biological reactions which are characterized by sigmoidal curves.  相似文献   

8.
Abstract

An investigation was conducted to determine the nature of decomposition products resulting from the interaction between humic acid and apatite and assess their availability to plant growth. Interaction analyses were performed by shaking 200 mg apatite with 0 to 800 mg/L HA or FA solutions at pH 5 or 7 for 0 to 12 hr. Phosphorus concentrations were determined in the supernatants by spectrophotometry. The nature of P‐humic acid complexes was determined by 31P NMR analysis. Availability of these dissolution products was studied by growing corn plants in aerated hydroponics to which 200 mg apatite and 0 to 800 mg/L HA were added at pH 5 or 7. The results indicated that the rate of dissolution of apatite was parabolic in regression with time, and increased by increasing the amounts of HA or FA applied from 100 to 800 mg/L The dissolution reaction was influenced by pH, because larger amounts of PO4 3‐ions were detected at pH 5 than at pH 7. 31P NMR spectroscopy indicated the presence of P‐humic acid complexes, previously believed to be humophosphate esters. The PO4 3‐ ion was complexed by HA at pH 7 or above, but PO4 3‐ appeared to be released again as adsorbed and free ions at pH <5.0. Plant performance corresponded with increased PO4 3‐concentrations at pH 5.0. No significant improvement over the control was observed in the growth of corn plants by apatite + HA treatments at pH 7. However, plant growth was increased significantly over the control by apatite + HA treatments at pH 5.0. Better growth performance of corn plants were noticed by apatite + HA than by KH2PO4 treatments at pH 5.0.  相似文献   

9.
We investigated the interacting effects of inorganic nitrogen and the main inorganic phosphorus form in dairy manure (dicalcium phosphate, CaHPO4) on growth, nutrient uptake, and rhizosphere pH of young maize plants. In a pot experiment, three levels of CaHPO4 (0, 167, and 500 mg P pot?1) were combined with nitrogen (637 mg N pot?1) applied at five NH4‐N : NO3‐N ratios (0 : 100, 25 : 75, 50 : 50, 75 : 25, and 100 : 0) and a nitrification inhibitor in a concentrated layer of a typical acid sandy soil from Denmark. 15N‐labeled NH4‐N was applied to differentiate the role of nitrification and to partition nitrogen uptake derived from NH4‐N. Among treatments including nitrogen, shoot biomass, rooting and phosphorus uptake were significantly higher at the five‐leaf stage when CaHPO4 was applied with NH4‐N : NO3‐N ratios of 50 : 50 and 75 : 25. In these treatments, rhizosphere pH dropped significantly in direct proportion with NH4‐N uptake. The fertilizers in the concentrated layer had a root‐inhibiting effect in treatments without phosphorus supply and in treatments with pure NO3‐N or NH4‐N supply. Increased nitrogen uptake as NH4‐N instead of NO3‐N reduced rhizosphere pH and enhanced acquisition of applied CaHPO4 by young maize plants, which may have positive implications for the enhanced utilization of manure phosphorus.  相似文献   

10.
N mineralization process (ammonification plus nitrification) in the surface 0-5 cm soil layers under shifting cultivation in northern Thailand was studied. Labile pool of organic matter extracted with a K2S04 solution at 1l0°C in an autoclave (fraction A) or by shaking at room temperature (fraction B) was used as factor to evaluate the N mineralization process which was examined in an incubation experiment. In the soils, in which the N mineralization pattern was fitted to a first order kinetics model, the content of (organic + NH4 +)-N in fraction B determined the initial rate of N mineralization. The soils, which showed a short lag time of less than 7 d both in the N mineralization and nitrification processes, had a high ratio of organic C to (organic + NH4 +)-N in fraction B, exceeding the value of 7. The soils, which showed a long lag time of more than 7 d only in the nitrification process, had a low pH(KCI) (less than 4.2). Thus, the rate of N mineralization was affected by the labile pool in fraction B or soil pH. On the other hand, there was a correlation between the N 0 + N max (inorganic N at 0 d + maximum amount of mineralizable N) value and the labile pool in the fraction A, suggesting that the N 0 + N max value depended on the contents of the labile pool.  相似文献   

11.
The effect of presubmergence and green manuring on various processes involved in [15N]‐urea transformations were studied in a growth chamber after [15N]‐urea application to floodwater. Presubmergence for 14 days increased urea hydrolysis rates and floodwater pH, resulting in higher NH3 volatilization as compared to without presubmergence. Presubmergence also increased nitrification and subsequent denitrification but lower N assimilation by floodwater algae caused higher gaseous losses. Addition of green manure maintained higher NH4+‐N concentration in floodwater mainly because of lower nitrification rates but resulted in highest NH3 volatilization losses. Although green manure did not affect the KCl extractable NH4+‐N from applied fertilizer, it maintained higher NH4+‐N content due to its decomposition and increased mineralization of organic N. After 32 days about 36.9 % (T1), 23.9 % (T2), and 36.4 % (T3) of the applied urea N was incorporated in the pool of soil organic N in treatments. It was evident that the presubmergence has effected the recovery of applied urea N.  相似文献   

12.
The effects of temperature and water potential on nitrification were investigated in two Iowa soils treated with Stay‐N 2000. The soils were incubated at 10, 20, and 30 °C after soil water potentials of ?1, ?10, or ?60 kPa were applied to each soil. A first‐order equation was used to calculate the maximum nitrification rate (K max), duration of lag period (t′), period of maximum nitrification (Δt), and termination period of nitrification (t s). The highest K max were 18 and 24 mg kg?1 d?1 nitrate (NO3 ?)–nitrogen (N), respectively, at 30 °C and ?10 kPa in both the Nicollet (fine‐loamy, mixed, superactive, mesic Aquic Hapludoll) and Canisteo (fine‐loamy, mixed, superactive, calcareous, mesic Typic Endoaquoll) soils and reduced to 4 and 16 mg kg?1 d?1 NO3 ?‐N when Stay‐N 2000 was added. The extension of t′ due to the addition of Stay‐N 2000 was as high as 7 d in the Nicollet soil at 10 °C and ?1 kPa and as little as 2 d in the Canisteo soil at 20 °C and ?10 kPa.  相似文献   

13.
Abstract

The effect of liming on mineralization and soil nitrifier activity (NA) was investigated with Brookston clay (pH 5.7) and Haldimand clay (pH 4.7). Liming increased the rate of mineralization in both soils but at a rate about 4‐times greater in Haldimand clay than Brookston clay. A significant increase in N mineralization due to liming occurred in both soils only when pH was raised above 6.0. The rate of mineralization was greater than nitrification in the Haldimand soil resulting in NH4 + accumulation. Nitrifier activity increased with liming of Brookston clay, but decreased in Haldimand clay after 15 days of incubation. There was a significant increase in nitrifier activity due to liming from 15 to 60 days in Haldimand clay. After 60 days nitrifier activity in limed treatments increased by five times over the unlimed control.

The nitrification of urea powder (1000 mg N.kg‐1) mixed into the soil was also studied in several soils incubated at 15°C for 28 days. There was evidence up to 14 days that nitrification of urea was correlated with initial nitrifier activity. Between 14 and 28 days, other factors such as soil pH and possible ammonia toxicity in coarser textured soils as well as nitrifier activity were important. Accumulation of nitrite occurred mainly in soils with a pH above 7.0 up to 28 days especially where nitrifier population enrichment was not done.  相似文献   

14.

Purpose

Long-term manure applications can prevent or reverse soil acidification by chemical nitrogen (N) fertilizer. However, the resistance to re-acidification from further chemical fertilization is unknown. The aim of this study was to examine the effect of urea application on nitrification and acidification processes in an acid red soil (Ferralic Cambisol) after long-term different field fertilization treatments.

Materials and methods

Soils were collected from six treatments of a 19-year field trial: (1) non-fertilization control, (2) chemical phosphorus and potassium (PK), (3) chemical N only (N), (4) chemical N, P, and K (NPK), (5) pig manure only (M), and (6) NPK plus M (NPKM; 70 % N from M). In a 35-day laboratory incubation experiment, the soils were incubated and examined for changes in pH, NH4 +, and NO3 ?, and their correlations from urea application at 80 mg N kg?1(?80) compared to 0 rate (?0).

Results and discussion

From urea addition, manure-treated soils exhibited the highest acidification and nitrification rates due to high soil pH (5.75–6.38) and the lowest in the chemical N treated soils due to low soil pH (3.83–3.90) with no N-treated soils (pH 4.98–5.12) fell between. By day 35, soil pH decreased to 5.21 and 5.81 (0.54 and 0.57 unit decrease) in the NPKM-80 and M-80 treatments, respectively, and to 4.69 and 4.53 (0.43 and 0.45 unit decrease) in the control-80 and PK-80 treatments, respectively, with no changes in the N-80 and NPK-80 treatments. The soil pH decrease was highly correlated with nitrification potential, and the estimated net proton released. The maximum nitrification rates (K max) of NPKM and M soils (14.7 and 21.6 mg N kg?1 day?1, respectively) were significantly higher than other treatments (2.86–3.48 mg N kg?1 day?1). The priming effect on mineralization of organic N was high in manure treated soils.

Conclusions

Field data have shown clearly that manure amendment can prevent or reverse the acidification of the red soil. When a chemical fertilizer such as urea is applied to the soil again, however, soil acidification will occur at possibly high rates. Thus, the strategy in soil N management is continuous incorporation of manure to prevent acidification to maintain soil productivity. Further studies under field conditions are needed to provide more accurate assessments on acidification rate from chemical N fertilizer applications.  相似文献   

15.
We studied the interacting effects on NH3 loss and grain yield of adding (1) urease inhibitors to retard the hydrolysis of urea (2) the algicide terbutryn to limit floodwater pH increases, and (3) C2H2 (provided by waxcoated calcium carbide) to prevent NH3 oxidation. The algicide treatment maintained the floodwater pH values below 8 for the first 3 days after the urea application and depressed the maximum values below 8.5 on subsequent days. As a consequence, NH3 loss was significantly (P<0.05) reduced in all treatments containing algicide. The addition of wax-coated calcium carbide effectively inhibited nitrification, as judged by the increased ammoniacal (NH3+NH4) N concentrations in the floodwater, However, these increased ammonical-N concentrations resulted in large losses of NH3. The results also showed that the effectiveness of a urease inhibitor cannot be judged solely from the ammonical-N concentrations in the floodwater of a single treatment with the inhibitor. Additional treatments with an algicide and a nitrification inhibitor are required to determine whether the low ammoniacal-N concentrations are caused by NH3 losses and nitrification. Thus N-(n-butyl)thiophosphorictriamide (NBPT) appeared to retard urea hydrolysis when judged by the low ammoniacal-N concentrations in the floodwater; however, treatments with NBPT, algicide, and C2H2 showed that the low concentrations were mainly a result of NH3 volatilization and nitrification. Even though NBPT did not completely inhibit urea hydrolysis, some treatments with this compound reduced NH3 losses and increased grain yields by up to 31%.  相似文献   

16.
Abstract

Laboratory and greenhouse experiments were conducted to determine the effects of rate of nitrapyrin and soil pH on nitrification of NH4 + fertilizer in soil, and growth and chemical composition of burley tobacco (Nicotiana tabacum L. cv. ‘KY ‐14'). Such experiments were needed to develop information for increasing efficiency of N fertilizer use and to lessen the fertilizer‐induced soil acidity and salt effects on tobacco plants.

Results for laboratory and greenhouse incubations indicated that nitrification proceeeded slowly below pH 5.0 and the nitrapyrin necessary to delay nitrification increased with both increasing soil pH and length of incubation time. Generally, nitrification could be delayed 30 days by nitrapyrin rates of 0.25 or 0.5 μg g‐1 regardless of soil pH. but rates of 1 μg g‐1 nitrapyrin or higher were required for 60 days and longer incubation times, particularly at higher soil pH.

Growth and morphology of tobacco plants were either unaffected, or affected positively, by low rates of nitrapyrin (up to 2 μg g‐1). However, rates of 4 μg g‐1 and above reduced total plant dry weight, reducing sugars and contents of mineral elements. Concentrations and content of plant NO3 ‐ N and Mn were greatly decreased by application of nitrapyrin. Values for most parameters measured increased with increasing soil pH. The data show that low rates of nitrapyrin may be used to alter the ratio of NO3 ‐ to NH4 + N absorbed by tobacco and possibly improve growth and safety of tobacco.  相似文献   

17.
胡敏酸对铵钾在粘土矿物上交互作用的影响   总被引：1，自引：0，他引：1  
Interaction of ammonium (NH+4) and potassium (K+) is typical in field soils. However, the effects of organic matter on interaction of NH+4 and K+have not been thoroughly investigated. In this study, we examined the changes in major physicochemical properties of three clay minerals (kaolinite, illite, and montmorillonite) after humic acid (HA) coating and evaluated the influences of these changes on the interaction of NH+4 and K+on clay minerals using batch experiments. After HA coating, the cation exchange capacity (CEC) and specific surface area (SSA) of montmorillonite decreased significantly, while little decrease in CEC and SSA occurred in illite and only a slight increase in CEC was found in kaolinite. Humic acid coating significantly increased cation adsorption and preference for NH+4, and this effect was more obvious on clay minerals with a lower CEC. Results of Fourier transform infrared spectrometry analysis showed that HA coating promoted the formation of H-bonds between the adsorbed NH+4 and the organo-mineral complexes. HA coating increased cation fixation capacity on montmorillonite and kaolinite, but the opposite occurred on illite. In addition, HA coating increased the competitiveness of NH+4 on fixation sites. These results showed that HA coating affected both the nature of clay mineral surfaces and the reactions of NH+4 and K+with clay minerals, which might influence the availability of nutrient cations to plants in field soils amended with organic matter.  相似文献   

18.
NH3 volatilization from surface-applied urea, diammonium phosphate (DAP), and calcium ammonium nitrate (CAN) was measured with chambers through which air was drawn continuously. Two sandy soils and two sandy loam soils, which had been treated with and without time for the last 25 years, were used for the experiments. The accumulated NH3 loss from CAN applied to an unlimed sandy soil was linearly related to time. For the other treatments the accumulated loss was exponentially related to time. The NH3 loss was exponentially related to the maximum soil pH of the fertilizer-amended soil, and was inversely related to the content of exchangeable H+. Due to the low cation exchange capacity of these light-textured soils the NH3 loss was not reduced as the soil CEC increased. The maximum pH after soil amendment was related to soil pH. Therefore, a model is proposed that relates the NH3 loss solely to fertilizers and soil pH. The NH3 loss was less than 5% from CAN, about 20% from DAP, and about 30% from urea, with the insignificant loss from urea applied to the unlimed sandy soil excluded. The NH3 loss from surface-applied DAP was related to the air flow rate and a transfer coefficient (K a) was estimated. K a increased exponentially with the flow rate. At a flow rate above 3.9 liters min–1 (20 volume exchanges min–1) no further increase was seen.  相似文献   

19.
Abstract

This trial was carried out to establish an appropriate nutrient solution for Aglaonema commutatum and to investigate the nutritional effects generated by modifications in the solution. Six treatments were tested: control (T0; pH 6.5, E.C. 1.5 dS m?1, 6 mmol L?1 NO3 ?‐N, and 6 mmol L?1 K+); high nitrogen (N) level (T1; 9 mmol L?1 6:3 NO3 ?–NH4 +); N form (T2; 6 mmol L?1 N‐NH4 +); high K+ level (T3; 12 mmol L?1 K+); high electrical conductivity (T4; E.C. 4 dS m?1, 25 mmol L?1 NaCl), and basic pH (T5; pH 8). At the end of the cultivation, leaf, shoot, and root dry weights and elemental concentrations were determined. Nutrient contents and total plant uptake were calculated from the dry weights and nutrient concentrations. Plant K+ uptake increased with application of K+ or basic nutrient solution. The uptake and transport of calcium (Ca) were enhanced by the use of NO3 ?‐N and inhibited by the presence of other cations in the medium (NH4 +, K+, Na+) and by basic pH. Magnesium (Mg) uptake increased with NO3 ?‐N application and with pH. Sodium (Na) uptake was the highest in the saline treatment (T4), followed by the basic pH treatment. Sodium accumulation was detected in the roots (natrophobic plant), where the plant generated a physiological barrier to avoid damage. Dry weight did not differ significantly (p<0.05) among treatments except in the NaCl treatment. These results may help in the formulation of nutrient solutions that take into account the ionic composition of irrigation water and the physiological requirements of plants.  相似文献   

20.
Abstract

Differences in characteristics of humic matter were investigated by solid‐state CP/MAS 13C NMR spectroscopy of whole (nontreated) materials and their extracted humic fractions. Samples used in the analysis were lignite, a commercial humate AG, and the Bh horizons of a Mascotte and a Lawnwood soil. Humic fractions were extracted by the 0.1 M NaOH or Na4P2O7 (pH 9.8) method. The humic (HA) and fulvic acid (FA) obtained were weighed and analysed for total acidity, carboxyl and phenolic‐OH group contents. Whole lignite, humate AG and soil samples, and the HA and FA fractions were analyzed by solid state CP MAS 13C NMR and infrared spectroscopy. Carbon, H, and N contents were determined by chemical analysis. NMR spectra of the combined HA+FA extracts resembled the spectra of the whole materials. No additional signals were detected, indicating that alien compounds were not produced during the extraction. The best spectra were obtained with HA samples produced by the NaOH method. These spectra closely resembled those of the untreated materials. Spectral and chemical differences noticed between the HA (or FA) fractions were attributed more to differences in origin than to the extraction procedure. Aliphatic, aromatic and carboxyl groups were the major components of HA from lignite and humate AG. In contrast, HA from the two Haplaquods were characterized by four major components: the aliphatic, polysaccharide, aromatic, and carboxyl groups. Regardless of origin, all the HA fractions contained similar functional groups, as indicated by their close similarities in infrared spectra.  相似文献   

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