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1.
Experiments were conducted with two typical paddy soils from China and a vermiculite to study the influence of iron oxides on the fixation and release of ammonium. Removing iron oxides, especially amorphous iron oxides, from the soils favoured the release of non-exchangeable NH4-N and stimulated the fixation of NH4-N in the presence of added (NH4)2SO4. Addition of artificial goethite and hematite to the original soils or to the soils free of iron oxides reduced the fixation of NH4+-ions. This effect was also observed with vermiculite. We conclude that the coating of clay minerals with iron oxides has an impact on the diffusion of NH4+-ions into and out of the interlayers of the clay minerals. The reduction and dissolution of iron oxides induced by low redox potential (Eh) after flooding of paddy soils is assumed to be an important mechanism controlling NH4+-fixation in paddy fields.  相似文献   

2.
An incubation experiment under aseptic and septic conditions using 15N-labelled NH4+-N and NO3–-N, was carried out to study the effect of N transformations after flooding on NH4+ fixation in a paddy soil from China. After flooding ammonification was favoured, providing NH4+ for fixation by clay minerals. NH4+ fixation was more pronounced under low redox potential (Eh) conditions. Close correlations existed between exchangeable NH4+, Eh, and non-exchangeable NH4+. Therefore, two major conditions for NH4+ fixation induced by flooding in paddy soil were found, namely flooding promoted net production of NH4+ due to the deamination of organic N and, in addition, decreased the Eh of the soil. A lower Eh was caused by reduction and dissolution of Fe oxide coating on the clay minerals' surfaces, eliminating the obstacles for NH4+ diffusing into or out of the interlayers of clay minerals. A higher concentration of exchangeable NH4+ from deamination of organic N would drive NH4+ diffusing from the soil solution into the interlayers of clay minerals. 15N-labelled NO3– incorporated into the flooded soil was not reduced to NH3. The addition of NO3– retarded the decrease in the soil Eh and, therefore, NH4+ fixation.  相似文献   

3.
Abstract

Fixation of the ammonium ion (NH4 +) by clay minerals is an alternate way of building the nitrogen (N) pool in soil to optimize N crop recovery and minimize losses. Clay minerals (illite, montmorillonite, and vermiculite) and an illitic Portnoeuf soil were used to compare NH4 + fixation abilities. Total N determination and X‐ray diffraction analysis were performed on each of the minerals and the Portnoeuf soil controls, and NH4 + saturated batches were subsequently desorbed by potassium chloride (KCl) after 4096 hours. Total N was determined for each employing either Kjeldahl digestion only, or pretreating with hydrofluoric‐hydrochloric acid (HF‐HCl) before the Kjeldahl digestion. The total N for the soil was 38% more after pretreatment with HF‐HCl. The total N determined after pretreatment with HF‐HCl for the NH4 + saturated and subsequently KCl desorbed minerals was found to be highest in vermiculite. The cation exchange acapacity (CEC) of each of the minerals was determined, and highest CEC was found in montmorillonite [83.07 cmol(+)/kg]. X‐ray diffraction analysis revealed collapse of the vermiculitic clay lattice from an initial d‐spacing of 13.1 angstrom to 10.4 angstrom after desorprion by KCl. This suggested the existence of sequestered NH4 + between the 2: 1 vermiculitic clay interlayer lattice.  相似文献   

4.
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   

5.
Abstract

In view of the agronomic and economic significance of NH4 fixation in soils, an attempt has been made to relate this to the most reactive mineral constituents of soils ‐ the clay minerals, under the temperature‐moisture regimes normal to tropical upland rice soils. Laboratory fixation study was done with NH4, concentrations similar to those common in soils upon N fertilization, and under alternate wetting and drying at ambient temperatures rather than at 100°C as in many published studies.

Results of the investigation show that soil clays with dominant vermiculite and montmorillonite fix the greatest proportion of applied NH4 (94 and 91%), followed by beidellite (72%) and x‐ray amorphous (45–64%) clays. Fixation is negligible (10%) in the clay with mineral suite consisting of hydrous mica, halloysite, and chlorite. Crystallinity of minerals seems to influence NH4 fixation appreciably.  相似文献   

6.
Displacement of NH4+ fixed in clay minerals by fertilizer 15NH4+ is seen as one mechanism of apparent added nitrogen interactions (ANI), which may cause errors in 15N tracer studies. Pot and incubation experiments were carried out for a study of displacement of fixed NH4+ by 15N‐labeled fertilizer (ammonium sulfate and urea). A typical ANI was observed when 15N‐labeled urea was applied to wheat grown on soils with different N reserves that resulted from their long‐term fertilization history: Plants took up more soil N when receiving fertilizer. Furthermore, an increased uptake of 15N‐labeled fertilizer, induced by increasing unlabeled soil nitrogen supply, was found. This ANI‐like effect was in the same order of magnitude as the observed ANI. All causes of apparent or real ANI can be excluded as explanation for this effect. Plant N uptake‐related processes beyond current concepts of ANI may be responsible. NH4+ fixation of fertilizer 15NH4+ in sterilized or non‐sterile, moist soil was immediate and strongly dependent on the rate of fertilizer added. But for the tested range of 20 to 160 mg 15NH4+‐N kg–1, the NH4+ fixation rate was low, accounting for only up to 1.3 % of fertilizer N added. For sterilized soil, no re‐mobilization of fixed 15NH4+ was observed, while in non‐sterile, biologically active soil, 50 % of the initially fixed 15NH4+ was released up to day 35. Re‐mobilization of 15NH4+ from the pool of fixed NH4+ started after complete nitrification of all extractable NH4+. Our results indicate that in most cases, experimental error from apparent ANI caused by displacement of fixed NH4+ in clay is unlikely. In addition to the low percentage of only 1.3 % of applied 15N, present in the pool of fixed NH4+ after 35 days, there were no indications for a real exchange (displacement) of fixed NH4+ by 15N.  相似文献   

7.
The fraction of nonexchangeable ammonium (NH4+) can play an important role in N cycling of soils as a sink (fixation) or a source (release) of NH4+. Recently fixed nonexchangeable NH4+ especially seems to be a significant source for N release. The aim of our study was to determine the effect of residence time on the kinetics of nonexchangeable NH4+ release from illite and vermiculite. Calcium-saturated illite and vermiculite, containing NH4+ that was “fixed” for one and 60 d, were extracted with a H-resin for 0.25 to 384 h. Both clay minerals “fixed” significantly more NH4+ in 60 d than in 1 d, but vermiculite “fixed” more NH4+ than illite. The kinetics of nonexchangeable NH4+ release from illite and vermiculite were well described by the Elovich equation and by a heterogeneous diffusion model. In vermiculite the percentage of nonexchangeable NH4+ release decreased from 84% to 78% when the time of fixation increased from 1 to 60 d. In illite time of residence has not influenced the complete release of newly fixed NH4+.  相似文献   

8.
钾对铵离子在蛭石矿物表面吸附与层间固定的影响   总被引：12，自引：0，他引：12  
在K+、NH4+不同施用顺序的情况下研究了蛭石对NH4+的晶层固定 ,证实了K+的存在对NH4+的矿物晶层固定不具有影响。在Ca2+-NH4+二元系统和Ca2+-NH4+-K+三元系统中 ,对NH4+在蛭石表面的吸附进行了研究 ,结果同样显示 ,K+对NH4+在蛭石表面的吸附位点不具有竞争作用。  相似文献   

9.
Summary The dynamics of basally applied 15N-labeled ammonium sulfate in inorganic and organic soil fractions of five wetland rice soils of the Philippines was studied in a greenhouse experiment. Soil and plant samples were collected and analyzed for 15N at various growth stages. Exchangeable NH4 + depletion continued after 40 days after transplanting (DAT) and corresponded with increased nitrogen uptake by rice plants. Part of the applied fertilizer was fixed by 2:1 clay minerals, especially in Maligaya silty clay loam, which contained beidellite as the dominant clay mineral. After the initial fixation, nonexchangeable 15N was released from 20 DAT in Maligaya silty clay loam, but fixation delayed fertilizer N uptake from the soil. Part of the applied N was immobilized into the organic fraction. In Guadalupe clay and Maligaya silty clay loam, immobilization increased with time while the three other soils showed significant release of fertilizer N from the organic fraction during crop growth. Most of the immobilized fertilizer N was recovered in the nondistillable acid soluble (alpha-amino acid + hydrolyzable unknown-N) fraction at crop maturity. Between 61% and 66% of applied N was recovered from the plant in four soils while 52% of fertilizer N was recovered from the plant in Maligaya silty loam. Only 20% – 30% of the total N uptake at maturity was derived from fertilizer N. Nmin (mineral N) content of the soil before transplanting significantly correlated with N uptake. Twenty-two to 34% of applied N was unaccounted for possibly due to denitrification and ammonia volatilization.  相似文献   

10.
盆栽和田间条件下土壤15N标记肥料氮的转化   总被引：14，自引：2，他引：14  
程励励  文启孝  李洪 《土壤学报》1989,26(2):124-130
利用15N在盆栽条件下研究了铵的矿物固定作用对肥料氮在三种土壤中转化的影响.结果表明,红壤性水稻土不固定肥料铵,但在白土和夹沙土中,56-77%的肥料氮被土壤矿物所固定,这些“新固定”的固定态铵的有效性很高,其中90%以上在30-50天内即被水稻所吸收,或者为微生物所利用转变为生物固定态氮.生物固定态氮对当季作物的有效性远较“新固定”的固定态铵的低.田间微区试验的结果还表明,甚至第二、三季作物吸收的残留肥料氮中,20-86%的氮也系来自固定态铵.作者认为,对具有较强固铵能力的土壤来说,只有了解铵的矿物固定作用,才能正确了解肥料氮的其它转化过程.  相似文献   

11.
Fate of fertilizer ammonium in soils with different composition of clay minerals in an incubation experiment In an incubation experiment with three different soils (gray brown podsolic soil from loess, alluvial gley, and brown earth, derived from basalt) the specific adsorption (fixation) and release of fertilizer NH4+ was investigated. In one treatment 120 mg NH4–N/kg soil was added, while the other treatment (control) received no nitrogen. Soils samples were taken every ten days and analyzed for nonexchangeable and exchangeable NH4+ and NO3?. The experimental results are showing that the specific adsorption of applied NH4+ was related to the type of clay minerals. While the loess soil, rich in illite, and the alluvial soil, rich in expansible clay minerals, bound about 40% of the added NH4+ specifically, the soil derived from basalt with mainly kaolinite bound only about 10 %. From the recently “fixed” fertilizer NH4+ about a half was nitrified during the incubation period of about 9 weeks. In the control there was no significant release of specifically bound NH4+. Obviously this NH4+ is located more deeply in the interlayers of the clay minerals and not available to microorganisms.  相似文献   

12.
Fixation and defixation of ammonium in soils: a review   总被引：2，自引：0，他引：2  
Fixed NH4+ (NH4+ f) and fixation and defixation of NH4+ in soils have been the subject of a number of investigations with conflicting results. The results vary because of differences in methodology, soil type, mineralogical composition, and agro-climatic conditions. Most investigators have determined NH4+ f using strong oxidizing agents (KOBr or KOH) to remove organic N and the remaining NH4+ f does not necessarily reflect the fraction that is truly available to plants. The content of native NH4+ f in different soils is related to parent material, texture, clay content, clay mineral composition, potassium status of the soil and K saturation of the interlayers of 2:1 clay minerals, and moisture conditions. Evaluation of the literature shows that the NH4+ f-N content amounts to 10–90 mg kg−1 in coarse-textured soils (e.g., diluvial sand, red sandstone, granite), 60–270 mg kg−1 in medium-textured soils (loess, marsh, alluvial sediment, basalt) and 90–460 mg kg−1 in fine-textured soils (limestone, clay stone). Variable results on plant availability of NH4+ f are mainly due to the fact that some investigators distinguished between native and recently fixed NH4+ while others did not. Recently fixed NH4+ is available to plants to a greater degree than the native NH4+ f, and soil microflora play an important role in the defixation process. The temporal changes in the content of recently fixed NH4+ suggest that it is actively involved in N dynamics during a crop growth season. The amounts of NH4+ defixed during a growing season varied greatly within the groups of silty (20–200 kg NH4+-N ha−1 30 cm−1) as well as clayey (40–188 kg NH4+-N ha−1 30 cm−1) soils. The pool of recently fixed NH4+ may therefore be considered in fertilizer management programs for increasing N use efficiency and reducing N losses from soils.  相似文献   

13.
Extensive use of chemical fertilizers in agriculture can induce high concentration of ammonium nitrogen(NH4+-N) in soil. Desorption and leaching of NH4+-N has led to pollution of natural waters. The adsorption of NH4+-N in soil plays an important role in the fate of the NH4+-N. Understanding the adsorption characteristics of NH4+-N is necessary to ascertain and predict its fate in the soil-water environment, and pedotransfer functions(PTFs) could be a convenient method for quantification of the adsorption parameters. Ammonium nitrogen adsorption capacity, isotherms, and their influencing factors were investigated for various soils in an irrigation district of the North China Plain. Fourteen agricultural soils with three types of texture(silt, silty loam, and sandy loam) were collected from topsoil to perform batch experiments. Silt and silty loam soils had higher NH4+-N adsorption capacity than sandy loam soils.Clay and silt contents significantly affected the adsorption capacity of NH4+-N in the different soils. The adsorption isotherms of NH4+-N in the 14 soils fit well using the Freundlich, Langmuir, and Temkin models. The models’ adsorption parameters were significantly related to soil properties including clay,silt, and organic carbon contents and Fe2+ and Fe3+ ion concentrations in the groundwater. The PTFs that relate soil and groundwater properties to soil NH4+-N adsorption isotherms were derived using multiple regressions where the coefficients were predicted using the Bayesian method. The PTFs of the three adsorption isotherm models were successfully verified and could be useful tools to help predict NH4+-N adsorption at a regional scale in irrigation districts.  相似文献   

14.
Abstract

Urea applications to soil are subject to loss by ammonia (NH3) volatilization, unless incorporated. It has been proposed that this loss can be reduced by stimulating populations of soil nitrifiers by an ammonium sulfate [(NH4)2SO4] pretreatment two to four weeks before urea application. The objective of this laboratory trial was to evaluate this concept with five diverse soils, two North American Mollisols and three South American Oxisols. The soils were incubated untreated for two weeks, followed by pretreatment with 0 or 5 kg nitrogen (N) ha‐1 as (NH4)2SO4, on a soil surface area basis. After another two weeks of incubation, the soils were treated with the equivalent of 0 or 50 kg N ha‐1 as urea. Ammonia loss was estimated after trapping into phosphoric acid (H3PO4). Ammonium sulfate pretreatment reduced NH3 loss with the two Mollisols and a sandy Oxisol and increased the recovery of the urea application as mineral [ammonium (NH4 +) + nitrate (NO3 ‐)] N in these soils. Little NH3 loss was detected from the two clay Oxisols, and (NH4)2SO4pretreatment did not influence NH3 loss or recovery of urea as mineral N. An example of a cropping system where this concept may have utility is discussed.  相似文献   

15.
Potassium (K+) and nitrogen [N, as the form of ammonium (NH4+)] are major nutrients for plant growth. Although there have been a number of studies on the kinetic fixation of potassium and ammonium ions in soils and clays, however, investigations on the kinetics of competitive fixation of these ions have been few, if any, especially by taking into account silt component of the soils. In this study, the kinetics of potassium and ammonium fixation were examined in the silt components of several soil samples. The results revealed that considerable amounts of K+ and in lesser amounts, NH4+ ions were fixed by silt components of the soils. Potassium fixation was strongly preferred over ammonium. To describe the fixation kinetics, seven mathematically models were evaluated. A comparison of the models showed that pseudo-second-order equation properly described the fixation of these ions by the silt components.  相似文献   

16.
A soil column method was used to compare the effect of drip fertigation (the application of fertilizer through drip irrigation systems, DFI) on the leaching loss and transformation of urea-N in soil with that of surface fertilization combined with flood irrigation (SFI), and to study the leaching loss and transformation of three kinds of nitrogen fertilizers (nitrate fertilizer, ammonium fertilizer, and urea fertilizer) in two contrasting soils after the fertigation. In comparison to SFI, DFI decreased leaching loss of urea-N from the soil and increased the mineral N (NH4+-N + NO3--N) in the soil. The N leached from a clay loam soil ranged from 5.7% to 9.6% of the total N added as fertilizer, whereas for a sandy loam soil they ranged between 16.2% and 30.4%. Leaching losses of mineral N were higher when nitrate fertilizer was used compared to urea or ammonium fertilizer. Compared to the control (without urea addition), on the first day when soils were fertigated with urea, there were increases in NH4+-N in the soils. This confirmed the rapid hydrolysis of urea in soil during fertigation. NH4+-N in soils reached a peak about 5 days after fertigation, and due to nitrification it began to decrease at day 10. After applying NH4+-N fertilizer and urea and during the incubation period, the mineral nitrogen in the soil decreased. This may be related to the occurrence of NH4+-N fixation or volatilization in the soil during the fertigation process.  相似文献   

17.
Chemical fixation of NH3 to soil organic matter was studied in two Swedish soils with different contents of organic matter: a clay soil with 2.3% C and an organic soil with 36.6% C. 15N‐labelled urea was applied at different rates to both sterilized and non‐sterilized soils. After 10 days, the soils were extracted and washed with K2SO4 and determined for total N and atom% 15N excess. Urea N was recovered as non‐extractable N in sterilized soil corresponding to 9.7% of supplied l5N‐labelled urea in the organic soil and 2.2% in the clay soil. Since no biological immobilization is thought to occur in the sterile soil, this non‐extractable N is suggested to be chemically fixed to soil organic matter. Owing to urea hydrolysis in the clay soil, pH increased from 6.3 to 9.3 and in the organic soil from 5.7 to 6.9 and 8.8, respectively, at the low and high urea supply.  相似文献   

18.
Field experiments were conducted to determine the effect of nitrogen (N) fertilizer forms and doses on wheat (Triticum aestivum L.) on three soils differing in their ammonium (NH4) fixation capacity [high = 161 mg fixed NH4-N kg?1 soil, medium = 31.5 mg fixed NH4-N kg?1 soil and no = nearly no fixed NH4-N kg?1 soil]. On high NH4+ fixing soil, 80 kg N ha?1 Urea+ ammonium nitrate [NH4NO3] or 240 kg N ha?1 ammonium sulfate [(NH4)2SO4]+(NH4)2SO4, was required to obtain the maximum yield. Urea + NH4NO3 generally showed the highest significance in respect to the agronomic efficiency of N fertilizers. In the non NH4+ fixing soil, 80 kg N ha?1 urea+NH4NO3 was enough to obtain high grain yield. The agronomic efficiency of N fertilizers was generally higher in the non NH4+ fixing soil than in the others. Grain protein was highly affected by NH4+ fixation capacities and N doses. Harvest index was affected by the NH4+ fixation capacity at the 1% significance level.  相似文献   

19.
Nitrogen mineralization and immobilization were investigated in two soils incubated with ammonium sulphate or pig slurry over a range of temperatures and moisture contents. A reduction in the mineralization of soil organic N was observed in soils incubated with 100 μg NH4+-Ng?1 soil as ammonium sulphate at 30°C but not at lower temperatures. Addition of 100 μg NH4+-N g?1 soil as pig slurry resulted in a period of nett immobilization lasting up to 30 days at 5°C. Although the length of the immobilization phase was shorter at higher temperatures the total N immobilized was similar. The subsequent rate of mineralization in slurry-treated soils was not significantly greater (P = 0.05) than in untreated soils. There was no evidence of any subsequent increased mineralization arising from the immobilized N or slurry organic N for up to 175 days. The rate of immobilization was found to increase with increasing moisture content, though the period of nett immobilization was shorter, so that the amount of N immobilized was similar over a range of moisture contents from 10 to 40%. Approximately 40% of the NH4+-N in the slurry was immobilized under the incubation conditions used.  相似文献   

20.
Cation‐exchange–capacity (CEC) results of calcareous soils and clays can be erroneous if the ammonium acetate method is used. In this study, a model is proposed to explain the process for systematic underestimation of the CEC. Seven clayey sediments from Germany with varying calcite and low organic‐C content were studied. After several exchange treatments with concentrated ammonium acetate (NH4Ac) solutions, the exchange population is assumed to be in homoionic ammonium form. Throughout the cation‐exchange experiment, calcite reacts with the NH4Ac exchange solution generating Ca2+ cations. During the necessary washing steps to remove excess salt, calcite dissolution is lower but still occurs. The permanently added Ca2+ ions compete successfully with NH , especially during the washing steps. This leads to a more or less partial biionic exchange population resulting in an underestimation of the CEC which is calculated based on NH concentration of the clay by Kjeldahl analysis. The biionic exchange population was proven using the new silver thiourea technique with presaturation of calcite, AgTU calcite . The clay with 148 g kg–1 calcite had a fraction of 16.4 cmol+ kg–1 exchangeable Ca2+. This is ca. 50% of the CEC of this clay being 31.8 cmol+ kg–1. For clays with similar mineralogical composition, this trend is proportional to the calcite content.  相似文献   

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