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1.
Clay (< 2 μ) from argillic horizons of sixteen Argids, Xerolls, and Ustalfs having either smectite or mica, or both, was analyzed for CEC, total K, X-ray diffraction peaks, and free swelling. The maximum and minimum limits of CEC and K for the smectite and clay mica were determined from the linear relationships of each of the four variables to the ratio of CEC or K to total charge (CEC + K). The theoretical maximum limits are 100 mequiv. of CEC/100 g for smectite and 5.1% K for clay mica. When the 14 Å peak of smectite is first lost from the suite of the two minerals, the CEC of clay mica is 40 mequiv./100 g and its K content is 3.4%. When the 10 Å peak of clay mica is first lost, the CEC of smectite is 70 mequiv./100 g and its K content is 1.3%. The limits that were set by X-ray peaks can be used for estimating the amounts of clay mica and smectite in soils of dry regions.  相似文献   

2.
Abstract

Crystalline minerals in anaerobically digested sewage sludges were determined by x‐ray diffraction analysis. Sludge samples were prepared for x‐ray analysis by either washing with H2O to remove soluble salts or oxidizing organic matter with H2O. A limited number of minerals are present as crystalline materials in sludge. Even though the sludges contained appreciable concentrations of Cu, Zn, Cd, Pb and Ni, no crystalline metal sulfides, phosphates, hydroxides, oxides or carbonates were found with the exception of a possible Cu, Zn carbonate hydroxide. All other crystalline components detected are common minerals such as quartz, feldspar, montmorillonite, chlorite, mica, dolomite and calcite.  相似文献   

3.
To prove the hypothesis that paddy rice utilizes soil nonexchangeable potassium (neK) and causes associated structural changes in clay minerals, K status and clay mineralogy of 22 surface soils from three paddy fields under long-term fertilizer management for 51–93 years were investigated. Soil neK content was determined as the difference between 1 mol L−1 hot HNO3 extractable K and 1 mol L−1 ammonium acetate exchangeable K. Clay mineralogy was identified by X-ray diffraction (XRD). The radiocesium interception potential (RIP), an index of frayed edge sites in the interlayer sites of 2:1 type clay minerals, was also determined. The neK contents under the -K and NPK treatments were considerably lower than those under the unfertilized treatment in all the fields, indicating the exploitation of soil neK by rice. XRD analysis of the clay samples revealed 7% shift from the 1.0 peak to 1.4 nm one under the -K treatment compared with the unfertilized one, and the amounts of neK were negatively correlated with those of RIP (p < .01), suggesting the expansion of interlayer spaces of the 2:1 type phyllosilicates such as mica due to the release of neK. In addition, the neK content positively correlated with K balance of the long-term experiments (p < .05). The differences of neK between unfertilized K and -K treatments corresponded to 22–157 kg K ha−1, or 0.42–1.68 kg K ha−1 year−1. In conclusion, utilization of considerable amount of soil neK under K depleted conditions should be considered to establish sustainable K management for paddy rice.  相似文献   

4.
An 8‐month greenhouse experiment with ryegrass (Lolium perenne L.) examined the relationship between the dynamics of potassium (K) reserves in soil and changes in clay minerals, using X‐ray diffraction. The capacity of soil to release K was consistent with its ability to supply it and was the highest in the soil samples collected from Laiyang (H1T2a), Harbin (H1T1) and Beibei (H2T4), followed by the sample from Jiangyan (H1T2b), and the lowest in the samples from Gao'an (H2T3a) and Wangcheng (H2T3b). Removal of soil K decreases the intensity of reflections for illite and increases that for interstratified clay minerals. The centre of gravity values of the clay fractions was significantly negatively correlated to the depletion of soil K reserves, as ascertained through chemical extraction or through plant action. The quantitative regression equations between the centre of gravity values and the dynamics of soil reserves of K can be used for predicting the release and plant availability of K even without growing a crop. Copyright © 2017 John Wiley & Sons, Ltd.  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.
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   

7.
Abstract

Using sequential extractions, total elemental analysis, and X‐ray diffraction, we have investigated the impact of the podzolization process on component composition of the clay fraction in the eluvial horizons of eight more or less podzolized Danish soils. The results indicate that podzolization is highly aggressive towards all clay components in the eluvial horizons eventually leading to their disintegration. The 2:1 layer silicate clay minerals, illite and chlorite, are first transformed into other 2:1 layer silicate clay minerals. After passing through a microcrystalline phase high in Si but low in Al, Fe, Mg, and K, they finally disintegrate completely. Even gibbsite and kaolinite disintegrate under the aggressive conditions, caused among other things by the presence of dissolved complex forming organic molecules in these horizons. Application of lime and fertilizers seems to be able to reverse the process in case of the 2:1 layer silicate clay minerals.  相似文献   

8.
Abstract

Potassium (K)‐release characteristics (PRC) of soil play a significant role in supplying available K. Information about PRC in the Hamadan soils is limited. The objective of this research was to study the PRC in nine soils from the Hamadan province by successive extraction with 0.01 M CaCl2 over a period of 2000 h. The correlation of kinetic equation rate constants with soil properties and garlic indices was also studied. The release of K was initially rapid. More than 60% of the total K released during the first 168 h. The amount of K released after 168 h varied among soils and ranged from 292.8 to 736.8 mg kg?1. The amount of K released after 2000 h was significantly correlated with K extracted by 1 M HNO3, 0.01 M CaCl2, and 0.1 M BaCl2, whereas it was not significantly correlated with other soil properties. Potassium‐release characteristics were evaluated using five kinetic equations. Statistical analysis showed that the Elovich equation described the K‐release kinetics. A plot of other equations shows a discontinuity in slope at 168 h. Thus, two equations were applied to segments of the total reaction time (2 to 168 and 168 to 2000 h). The release‐rate constants (slope) in segment 1 are higher than in segment 2. The release‐rate constant of the Elovich equation and the zero‐order equation in two segments were significantly correlated with 1 M HNO3, 0.01 M CaCl2, and 0.1 M BaCl2. Rate constants of the other equations were not significantly correlated with soil properties. The release‐rate constants of the Elovich equation and release‐rate constants of the zero‐order equation in two segments were significantly correlated with garlic indices. Rate constants of other equations were not significantly correlated with garlic indices. The results of this research showed that the Elovich and zero‐order equations can be used to describe K‐release characteristics.  相似文献   

9.
Different extraction methods are used world‐wide in routine soil analysis to estimate long‐term potassium (K) reserves for plants. In Sweden, K extracted with 2 M HCl at 100°C (KHCl) is frequently used, although with limited understanding of the phases extracted. In the present study, we quantified the effects of this extraction on soil minerals in particle size fractions ranging from clay to sand, and estimated their relative contribution to KHCl. The study included three Swedish long‐term agricultural field experiments with texture ranging from loamy sand to silty clay, as well as mineral specimens of K feldspar. Total weight loss of particle size fractions was determined, and quantitative and differential X‐ray powder diffraction (QXRD, DXRD), applied on solids before and after extraction, was used to quantify the dissolution of individual mineral phases. QXRD and DXRD included spray‐drying of samples, addition of an internal standard and full pattern fitting, where a combination of mineral‐standard XRD traces was matched with the experimental one. Our results show that KHCl was primarily associated with clay minerals concentrated in the two finest fractions (2–20 and < 2 μm). Highly expandable and mixed‐layer phyllosilicates were quantitatively the most important minerals dissolved. The K was released from micaceous layers in mixed‐layer phyllosilicates with a vermiculitic character. Whether di‐ or trioctahedral, a shared property of the dissolved phases was that they were rich in Fe. In the loamy sand, the coarser fractions (20–2000 μm), where feldspars were prominent, accounted for 35% of KHCl. According to DXRD, there was no significant decrease in K feldspars in any of the samples, and KHCl data for the feldspar specimens suggest that clay minerals contributed at least 70% of KHCl also in the loamy sand. Our study provides insights about the soil minerals that contribute to the long‐term K delivery capacity of soils and an explanation for the prior observation that KHCl is a dynamic fraction that can be affected by management.  相似文献   

10.
Abstract

The Ae, Bhf and Bf horizons of two podzolic soils from the Appalachian and Laurentian Highlands were treated with various reagents to remove the amorphous material prior to X‐ray diffraction analysis. Treatments were Na citrate, NaOH, Tiron, DCB and modified DCB, with a lower solid:liquid ratio. Samples treated with NaOH, Tiron and DCB were subsequently extracted with citrate. The latter extraction was necessary to remove Fe2O3 and SiO2 that was not solubilized in the first treatment. The effectiveness of the reagents to extract SiO2, Al203 and Fe2O3 decreased in the following order:

DCB 1:1 > Tiron = DCB > citrate > NaOH

The total weight loss of the samples represented about 1.8 times the sum of the oxides and reached up to 70% of the Laurentian Bf sample. Organic matter accounted for a part of the weight loss and its removal was more complete in the less crystalline samples of the Laurentian profile. Tiron was the best reagent to improve the X‐ray diffraction patterns, closely followed by DCB 1:1 treatment.

Removal of amorphous material and organic matter resulted in a decrease of the cation exchange capacity of the clay fraction, from a maximum of 73.5 meq / 100 g in the Laurentian profile to a minimum of 3.2 meq / 100 g in the Appalachian profile.

The results suggested that in the Laurentian profile, very poorly crystallized minerals possibly contributed to a part of the extracted material.  相似文献   

11.
Abstract

Potassium (K) fixation and release in soil are important issues in long‐term sustainability of a cropping system. Fixation and release behavior of potassium were studied in the surface and subsurface horizons in five benchmark soil series, viz. Dhar, Gurdaspur, Naura, Ladowal, and Nabha, under rice–wheat cropping system in the Indo‐Gangetic plains of India. Potassium fixation was noted by adding six rates of K varying from 0 to 500 mg kg?1 soil in plastic beakers while K release characteristics were studied by repeated extractions with 1 M HNO3 and 1 M NH4OAc extractants. The initial status of K was satisfactory to adequate. Potassium fixation of added K increased with the rate of added K irrespective of soil mineralogy and soil depth. Soils rich in K (Ladowal and Nabha) fixed lower amounts (18–42%) of added K as compared to Gurdaspur, Dhar, and Naura (44.6–86.4%) soils low in K. The unit fertilizer requirement for unit increase in available K was more in low‐K soils. The study highlights the need for more studies on K fixation in relation to the associated minerals in a particular soil. Potassium‐release parameters such as total extractable K, total step K, and CR‐K varied widely in different soil series, indicating wide variation in the K‐supplying capacity of these soils. K released with 1 M NH4OAc extractant was 20–33% of that obtained with 1 M HNO3. Total extractable K using 1 M HNO3 varied from 213 to 528 mg kg?1 and NH4OAc‐extractable K ranged from 71 to 312 mg kg?1 soil in surface and subsurface layers of different soil series. The Ladowal and Nabha series showed higher rates of K release than Gurdaspur, Dhar, and Naura series, indicating their greater K‐supplying capacity.  相似文献   

12.
粘粒矿物对土壤特性和肥力的意义是众所周知的。土壤胶体的特性主要决定于粘粒矿物的类型及其数量。随着土壤科学研究的进展,粘粒矿物组成的分析工作,已由定性分析逐渐进入到定量分析。在粘粒矿物的鉴定中,X射线分析是一个很重要的手段,也有用来进行粘粒矿物的定量分析,但由于不同土壤中的矿物结晶程度差异很大,所以侧定的准确性较差。因此,在土壤粘粒矿物分析方面,X射线一般只能作为定性和半定量之用,其分析结果往往用“主导”“伴随”“较多~较少”等术语来表示。目前这种表示粘粒矿物组成的方法已不能满足研究工作的需要,何况不同学者的判读标准又很难一致。  相似文献   

13.
Abstract

The effect of sesquioxides on the mechanisms of chemical reactions that govern the transformation between exchangeable potassium (Kex) and non‐exchangeable K (Knex) was studied on acid tropical soils from Colombia: Caribia with predominantly 2∶1 clay minerals and High Terrace with predominantly 1∶1 clay minerals and sesquioxides. Illite and vermiculite are the main clay minerals in Caribia followed by kaolinite, gibbsite, and plagioclase, and kaolinite is the major clay mineral in High Terrace followed by hydroxyl‐Al interlayered vermiculite, quartz, and pyrophyllite. The soils have 1.8 and 0.5% of K2O, respectively. They were used either untreated or prepared by adding AlCl3 and NaOH, which produced aluminum hydroxide. The soils were percolated continuously with 10 mM NH4OAc at pH 7.0 and 10 mM CaCl2 at pH 5.8 for 120 h at 6 mL h?1 to examine the release of Kex and Knex. In the untreated soils, NH4 + and Ca2+ released the same amounts of Kex from Caribia, whereas NH4 + released about twice as much Kex as Ca2+ from High Terrace. This study proposes that the small ionic size of NH4 + (0.54 nm) enables it to enter more easily into the K sites at the broken edges of the kaolinite where Ca2+ (0.96 nm) cannot have access. As expected for a soil dominated by 2∶1 clay minerals, Ca2+ caused Knex to be released from Caribia with no release by NH4 +. No Knex was released by either ion from High Terrace. After treatment with aluminum hydroxide, K release from the exchangeable fraction was reduced in Caribia due to the blocking of the exchange sites but release of Knex was not affected. The treatment increased the amount of Kex released from the High Terrace soil and the release of Knex remained negligible although with Ca2+ the distinction between Kex and Knex was unclear. The increase in Kex was attributed to the initially acidic conditions produced by adding AlCl3 which may have dissolved interlayered aluminum hydroxide from the vermiculite present, thus exposing trapped K as exchangeable K. The subsequent precipitation of aluminum hydroxide when NaOH was added did not interfere with the release of this K, and so was probably formed mostly on the surface of the dominant kaolinite. Measurement of availability of K by standard methods using NH4 salts could result in overestimates in High Terrace and this may be a more general shortcoming of the methods in kaolinitic soils.  相似文献   

14.
The release of non-exchangeable potassium from 24 calcareous soils of divergent mineralogy, from southern Iran, was examined. Sand, silt and clay particles were fractionated after dispersion with an ultrasonic probe. Samples were extracted with 0.01 M CaCl2 for 30 successive 2-h periods. The clay fraction released the largest amount of K in each soil. Cumulative K released ranged from 175 to 723, 35 to 128, and 71 to 146 mg kg?1 contributing 20–90, 4–39 and 2–54% for clay, silt and sand fractions, respectively. The lower proportion of K released from sand and silt fractions can be explained by the presence of a high content of CaCO3 and quartz in these fractions. The release kinetics for the non-exchangeable K data showed that parabolic diffusion and power function were the best fitting kinetic models. This indicated that slow diffusion of K from the mica interlayer positions is the main rate-controlling process. Cumulative K released and constant b values of parabolic diffusion model correlated significantly with the mica content of the clay fraction.  相似文献   

15.
Abstract

The 5 Msodium hydroxide (NaOH) chemical treatment was applied to the silt and clay fractions of three Chilean fertilized soils derived from volcanic materials (one Ultisol and two Andisols) in order to selectively concentrate iron oxides. The treatment was sequentially applied and results were followed by x‐ray diffraction and Mössbauer spectroscopy. In all samples, dissolution chemical treatment concentrated iron oxides in variable degrees; and both, Mössbauer spectra and x‐ray diffraction patterns were significantly improved after three successive hot NaOH treatments. Best results were obtained for the Ultisol sample which is the oldest soil with the lowest organic matter content. The Mössbauer spectrum after three NaOH treatments of Ultisol silt fraction reveals characteristic features of partially oxidized magnetite, leading to two probability profiles of the hyper‐fine field distribution: One of them due to mixed valence iron (Fe3+/2+) ions in octahedral sites [8=0.59 mm s‐1, 2≥ Q =0.02mm s ‐1, with a maximum hyper‐fine field at Bhf(max)=46.2 tesla]; the other distribution profile encompasses contribution from Fe3+ in tetrahedral sites [δ=0.30 mm s‐1, 2?Q =‐0.04 mm s‐1 , and Bhf(max)=48.2 tesla].  相似文献   

16.
Abstract

The potassium (K) supplying capacity of a deeply weathered profile developed over granite from Peninsular Malaysia was investigated by employing the quantity‐intensity (Q/I) approach. The values of potential buffering capacity (PBCK), labile K (KL), specific K (KO), and specific K sites (KX) were considerably higher in the saprolite zones as compared to the solum layers. This indicated that depletion of K on cropping would be faster in the solum materials than in the saprolites. Potassium equilibrium activity ratio was in the sequence: solum > middle saprolite > upper saprolite. Free energy values showed low, but sufficient, level of available K reserve in this profile. The relationships of Q/I parameters with physico‐chemical characteristics and clay mineralogy of the profile were discussed. The changes in the Q/I parameters as a function of depth were found to be associated with the contents of clay and organic matter in the solum, while in the saprolites, the clay mineralogy which composed mainly of K‐feldspar, mica, and mica‐smectite seemed to be the main factor.  相似文献   

17.
Abstract

A method employing fusion of soil clay samples with lithium metaborate (1:5 ratio) in a furnace at 1050°C for 1 hr. subsequent dissolution of the fused sample in 4% HNO3. and elemental analysis for Si, Al, Fe, Ca, Mg, K, and Ti by atomic absorption spectrometry was compared with the X‐ray fluorescence (XRF) fused disc technique for analysis. Duplicated analyses were performed on 15 clay samples from soils of the southern U.S and three API reference samples. The mean total percent recovery by this method was excellent (100.14 ± 2.85). Elemental oxide quantities in terms of SiO2. Al2O3, Fe2O3, MgO, CaO and K2O determined by atomic absorption/flame emission (AA/FE) spectroscopy were in good agreement with values measured by x‐ray fluorescence (XRF) on the same subsamples (r = 0.89* to 0.98**). but somewhat more variable on subsamples seperated from different pretreatments (r = 0.70* to 0.97** ). The method, which has also been tested on 36 additional clay samples from a variety of Kentucky soils with total percent recoveries ranging from 96.5 ‐ 103.5%. demonstrated no bias due to mineralogy with respect to mixed, montmorillonitic. and siliceous classes. This technique presents numerous advantages over other elemental analysis techniques utilizing fusion, dissolution, or XRF spectroscopy with respect to time, effort and cost. With the introduction of inductively‐coupled plasma (ICP) emission spectroscopy. efficiency can be additionally improved.  相似文献   

18.
Abstract

To evaluate the impact of soil clay mineralogy on the utilization efficiency of potassium fertilizers by rice, potassium fixation studies were made on fourteen soil clays having a range of mineralogical compositions. Soil clay with monomineralic beidellite fixed the highest proportion (76%) of the added potash, followed by clays containing either dominant or major vermiculite (51–66%). Fixation was significantly less severe (<35%) in vermiculitic clays containing hydrous mica. All the clays with mineralogical suites without beidellite or vermiculite, but consisting of montmorillonite, chlorite, hydrous mica, halloysite, kaolinite, and x‐ray amorphous material did not fix appreciable amounts (<18%) of the applied potassium.  相似文献   

19.
To avoid over‐fertilization of potassium (K) and thereby a mineral composition in the grass crop not optimal for animal health, estimation of K release from soil is important. The analytical methods should therefore predict the total K release. Furthermore, to minimize costs for the farmers they should provide information which remains valid over a period of several years. The relationship between different soil extraction procedures for K and K uptake in ley for three subsequent years after soil sampling was studied in 19 field experiments on a range of mineral soil types in Norway. Potassium determined with solutions that extracted exchangeable K or parts of exchangeable K (0.01 M CaCl2, 0.5 M NaHCO3, 1 M NH4oAc, or ammonium acetate lactate) was significantly (p < 0.05) related to the K yield only in the 1st yr after soil sampling. Potassium extracted with boiling in 1 M or 2 M HNO3 was significantly related to the K yield only in the 2nd and 3rd yr. Potassium extracted with cold 2 M HCl, boiling 0.1 M HNO3 or 0.5 M HNO3 was significantly related to the K yield in all 3 yr after soil sampling. Among these extractants, 0.1 M and 0.5 M HNO3‐extractable K were better predictors of K uptake than 2 M HCl‐extractable K. These three extractants release some non‐exchangeable K in addition to exchangeable K. The fraction of 1 M HNO3‐K extractable with 0.1 M HNO3 varied from 4% to 45%, whereas from 15% to 78% of 1 M HNO3‐K was extractable with 0.5 M HNO3. Consequently, the more easily releasable fraction of K extracted by boiling with 1 M HNO3 varied considerably between different sites.  相似文献   

20.
Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L?1 nitric acid (HNO3) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L?1 ammonium acetate (NH4OAc) and 1.0 mol L?1 HNO3 extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.  相似文献   

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