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1.
Abstract

Three extraction methods for aluminium and two for iron were compared with phosphate sorptivity (Bache and Williams index) for 40 tropical and 40 British soil samples. Extractable aluminium was well correlated with phosphate sorptivity in both groups, but extractable iron was well correlated only in British soils. In general methods which extracted more sesquioxides gave higher correlation coefficients. With aluminium, N ammonium acetate (pH 4.8) or 0.1N HCl gave better correlation than N KCl, while with iron dithionitecitrate was better than 0.1N HCl.  相似文献   

2.
The phosphate adsorption capacity (Pmax) of samples from various horizons of five Danish podzolized soils were investigated before and after organic matter removal. Removal of organic matter had no direct influence on Pmax suggesting that organic matter did not compete with phosphate for adsorption sites. In the soils investigated aluminium and iron oxides were the main phosphate adsorbents. Thus, more than 96% of the variation in Pmax could be accounted for by poorly crystalline aluminium and iron oxides (extractable by oxalate) and by well-crystallized iron oxides (taken as the difference between dithionite-citrate-bicarbonate-extractable iron and oxalate-extractable iron). Organic matter affected phosphate adsorption indirectly by inhibiting aluminium oxide crystallization. The resulting poorly crystalline oxides had high Pmax. In contrast, the influence of organic matter on the crystallinity of the iron oxides, and therefore on their capacity to adsorb phosphate, seemed limited.  相似文献   

3.
Fourteen soils from Colombia and Brazil provided a wide range of sorption characteristics. Curves of sorbed phosphate that was exchangeable to 32P were described by Freundlich's equation, and of non-exchangeable phosphate by Temkin's equation. Exchangeable phosphate was associated with aluminium in poorly-crystalline oxides and in organic complexes. Non-exchangeable phosphate was related to aluminium in organic complexes, and especially to the ratio of AI/C in them. In Nigerian soils similar mechanisms controlled sorption of phosphate but oxides and organic complexes of iron were important. The concentration of phosphate in solution when affinities of soil for exchangeable and non-exchangeable phosphate are equal, and the importance of organic matter, are discussed in relation to soil management and to responses of crops to fertilizer phosphate. The results indicate that sorption curves should not be split into sections.  相似文献   

4.
磷矿粉在橡胶园不同母质砖红壤中溶解特性研究   总被引：1，自引：0，他引：1  
研究表明大多数热带地区酸性土壤上施用磷矿粉能取得与水溶性磷肥相当的肥效。目前橡胶树等热带作物施肥实践中长期施用水溶性磷肥,磷矿粉在热带胶园土壤中的应用研究较少。为此,本文通过室内培养试验研究了采自云南昆阳磷矿(KPR)和江西吴村磷矿(WPR)2种品位磷矿粉在砂页岩、花岗岩、片麻岩、浅海沉积物和玄武岩等5种母质发育的10个胶园砖红壤中的溶解特性和有效性动态变化。结果表明:2种磷矿粉在10个砖红壤上的溶解量均随着培养时间的延长不断增加。对2种磷矿粉在砖红壤中的溶解动力学过程模拟效果最好的是Elovich方程,其次是Langmuir方程,Mitscherlich方程模拟效果最差。2种磷矿粉在玄武岩发育砖红壤上平均最大溶解量分别是砂页岩发育砖红壤、花岗岩发育砖红壤、片麻岩发育砖红壤和浅海沉积物发育砖红壤的2.16倍、1.73倍、2.49倍和2.39倍。2种磷矿粉在10个土壤中最大溶解量均与土壤有机质含量、水解性总酸、游离态氧化铁含量和CEC呈显著性正相关,溶解速率均与土壤水解性总酸、游离氧化铁和CEC呈显著正相关关系。经逐步回归发现:土壤游离氧化铁含量可能是决定磷矿粉在砖红壤中最大溶解量的第1因素,土壤磷吸附常数K值和CEC则可能分别是影响KPR和WPR在砖红壤中溶解速度的第1因素。2种磷矿粉施用后所有土壤有效磷含量均出现不同程度的增加,但不同土壤、不同培养时间有效磷增加量存在差异。本研究显示,将磷矿粉优先施用在玄武岩发育砖红壤可能会取得相对较好的效果;与KPR相比,WPR作为中低品位磷矿粉也可能同样有效。  相似文献   

5.
Abstract

The amounts and forms of zinc in twenty surface soils from Canterbury and Southland, New Zealand were determined using a sequential fractionation scheme. Total soil zinc concentrations ranged from 38.1 mg#lbkg‐1 to 113.8 mg#lbkg‐1. Although the proportions of zinc found in individual fractions varied between soils, on average approximately 3% occurred as exchangeable zinc, 5% as organic‐bound zinc, 9%, 18%, 24% was associated with manganese, amorphous iron and crystalline iron oxides, respectively, and 40% was in the residual fraction. In a group of soils formed in greywacke alluvium or loess, exchangeable zinc was inversely related to soil pH. Within the same group of soils, those of similar age with greater concentrations of total and organic‐bound zinc were present in imperfectly‐ and poorly‐drained soils compared with well‐drained soils. Zinc extracted from the soils with a range of reagents used to assess ‘plant available’ zinc was correlated strongly with the concentrations of zinc present in the exchangeable and organic‐bound zinc fractions.  相似文献   

6.
The iodine content in successive 10 cm horizons of eighteen soil profiles from England and Wales was determined and correlated with contents of‘free’ aluminium and iron oxides (oxalate-soluble) and organic matter. The pattern of change in iodine content with depth varied considerably with soil type. In the rendzina soils, the content was relatively high in the surface 10 cm but declined markedly with depth. In the podsols, iodine was low at the surface but increased in the B horizon: in one of these soils an iron pan of about 1 cm thickness had an iodine content as high as 37.6 mg/kg. In two soils derived from Ordovician, and one from igneous, rock material, the iodine content was relatively high (up to 25 mg/kg) with maximum values at intermediate depths. In contrast, soils derived from river alluvium and from lowland clays generally had low iodine contents (< 6 mg/kg) which showed little variation with depth in the profile. In a peat soil the iodine content was relatively high in the horizons above 60 cm but was low (1. 3 mg/kg) in the underlying clay. In all 154 samples from the eighteen sites, iodine content was closely correlated with oxalate-soluble aluminium (r= 0.834***) but not with oxalate-soluble iron (r= 0. 35) or organic matter (r= 0.37). However, in the five most acidic soils, with pH below 4. 8, the iodine content was more closely correlated with iron than with aluminium.  相似文献   

7.
A study on the distribution of free iron and manganese oxides was conducted in soils developed on calcareous alluvial deposits under subhumid climatic conditions, in Western Greece. Soil samples from two well drained soils and from two poorly drained soils, classified as Alfisols, were collected and used in this study. After certification of soil homogeneity the acid ammonium oxalate and dithionite-citrate-bicaxbonate methods were used to extract free iron and manganese oxides from the samples. Iron oxides extracted by the dithionite-citrate-bicarbonate method (Fed) were significantly higher than the iron oxides extracted by the ammonium oxalate method (Feo), indicating that a considerable fraction is present in crystalline forms, independent of drainage status. A confirmation of free iron oxides and fine clay was detected. The ratios Feo/Fed and (Fed-Feo)/total Fe (Fet) could not be used to distinguish the well drained soils from the poorly drained soils. Manganese movement in a soluble form is independent of the fine clay.  相似文献   

8.
土壤组分对广东省酸性水稻土磷吸附参数的影响   总被引：9，自引：2，他引：7  
Soil components affecting phosphate sorption parameters were studied using acid paddy soils derived from basalt, granite, sand-shale and the Pearl River Delta sediments, respectively, in Guangdong Province.For each soil, seven 2.50 g subsamples were equilibrated with 50 mL 0.02 mol L-1 (pH=7.0) of KCl containing 0, 5, 10, 15, 25, 50 and 100 ng P kg-1, respectively, in order to derive P sorption parameters (P sorption maximum, P sorption intensity factor and maximum buffer capacity) by Langmuir isotherm equation. It was shown that the main soil components influencing phosphate sorption maximum (Xm) included soil clay, pH,amorphous iron oxide (Feo) and amorphous aluminum oxide (Alo), with their effects in the order of Alo ＞Feo ＞ pH ＞ clay. Among these components, pH had a negative effect, and the others had a positive effect.Organic matter (OM) was the only soil component influencing P sorption intensity factor (K). The main components influencing maximum phosphate buffer capacity (MBC) consisted of soil clay, OM, pH, Feo and Alo, with their effects in the order of Alo ＞ OM ＞ pH ＞ Feo ＞ clay. Path analysis indicated that among the components with positive effects on maximum phosphate buffer capacity (MBC), the effect was in the order of Alo ＞ Feo ＞ Clay, while among the components with negative effects, OM ＞ pH. OM played an important role in mobilizing phosphate in acid paddy soils mainly through decreasing the sorption intensity of phosphate by soil particles.  相似文献   

9.
R. Mandal  A. Islam 《Geoderma》1979,22(4):315-321
Concentrations of inositol mono-, di- and tri-, tetra-, penta- and hexaphosphate ranged from 5.0 to 12.5, 10.0 to 27.6, 20.0 to 45.0, 22.5 to 64.6, and 20.0 to 275.4 ppm, respectively, in samples of soils that were poorly drained and mostly derived from alluvium. Multiple correlation suggested that the amounts of esters of inositol phosphate other than inositol monophosphate were significantly correlated with organic phosphorus, total phosphorus, organic carbon, total nitrogen, inositol phospate, clay, exchangeable iron and aluminium, and pH. Individually, inositol hexa-, penta-, and di- and triphosphates were significantly correlated with organic phosphorus, total phosphorus, organic carbon, total nitrogen, inositol phosphate, and exchangeable iron and aluminium; inositol tetraphosphate with organic carbon, total nitrogen, inositol phosphate, and exchangeable iron and aluminium; inositol monophosphate with none.  相似文献   

10.
An ultrasonic method has been used to measure the stability index, σ, for each horizon of six soils. They provided three soil series comparisons: Hanslope-Ragdale, Evesham-Denchworth and Flint-Salop, in which the first-named series in each pair is ‘rarely problematic’, and the second ‘commonly problematic’ in management. The results for the top soils are presented in terms of the relationship between σ and the concentrations of those soil constituents likely to contribute to stability of aggregates: organic matter, clay, iron and aluminium oxides, and calcium carbonate. Regression analysis indicates significant correlations for all except the iron and aluminium oxide components. For each soil pair, the ultrasonic measures of stability did not reflect soil management experience, either for surface or sub-soil horizons. In general the commonly problematic soil appeared to have the same if not higher stability than its rarely problematic partner. Ultrasonic measurement of stability to dispersion, whilst indicating possible mechanisms of soil aggregate formation and breakdown, gives little help in identifying soil management potential.  相似文献   

11.
红壤基质组分对磷吸持指数的影响   总被引：8，自引：1，他引：7  
在红壤旱地肥料长期定位试验(始于1988年)中,选取了无机肥试验区的NPK、NP、NK、PK,有机无机配施试验区的CK、CK+猪厩肥(BM)及CK+花生秸秆(SR)等7个施肥处理土壤,测定了土壤磷吸持指数(Phosphate sorption index,PSI),分析了PSI与红壤最大吸磷量(Xm)的相关关系,讨论了土壤pH、有机质、黏粒、铁铝氧化物及无机磷酸盐等基质组分对PSI的影响。结果表明:长期施磷或配施有机肥均可显著降低红壤PSI值,随着土壤pH的升高、有机质及铁结合态磷酸盐(Fe-P)含量的增加,红壤PSI显著降低;土壤游离铁铝氧化物及黏粒含量越高,PSI也越大。PSI与Xm呈显著线性相关关系(Xm=0.5PSI+412.8,n=15,r=0.967**,p<0.01),因此,可以用PSI替代Xm来表征土壤固磷能力,亦可由PSI的大小来推断土壤磷的供磷能力。  相似文献   

12.
Both phosphate and metal cations such as zinc can be retained by oxides of iron and aluminium. Yet the phosphate-retaining and zinc-retaining materials in soil appear to differ in their behaviour from that of pure oxides of iron and aluminium. In most soils, the electrostatic potentials of retaining materials appear to be negative at normal soil pH values. The changes in potential with pH, and consequent change in retention, also appear to differ from those of pure oxides. A model of a pure oxide was modified in an attempt to simulate the observed behaviour of soil. The most effective modification was to include a negative charge in the oxide. Such a charge could have arisen from solid–state diffusion of anions into the oxide, or by close association with permanently charged clays. The inclusion of this charge changes the direction of the effect of pH on phosphate retention. If the amount of negative charge is large enough, the paradoxical situation can arise in which the potential of a ‘variable-charge’ surface is not affected by pH. This is consistent with observed effects of pH on zinc retention by soils.  相似文献   

13.
Abstract

In nineteen surface horizons of red Mediterranean soils from various locations of Greece, phosphorus (P) sorption experiments were conducted and the sorption characteristics were studied in relation to soil properties. Phosphate sorption data were fitted both to the Langmuir and Freundlich equations. From these equations, the following P sorption parameters were determined from the Freundlich equation, X = ACn, the parameters A (the phosphate sorbed at C = 1 mg P/L), n (the P sorption intensity), the P sorption index (PS = X/log C) and maximum P sorption (Xmfr). From the Langmuir equation, C/X = 1/KXm + C/Xm, the parameters K (showing the bonding energy), maximum P sorption (Xmla), the quantity of P adsorbed at a standard concentration of 0.2 mg P/L (P0.2), and P maximum buffering capacity (PMBC). The Freundlich parameter A was strongly correlated to the clay and sesquioxides ("free”; iron and aluminum oxides and amorphous iron oxides) content. Seventy‐four percent of the variance of this parameter was explained by clay and “free”; iron (Fe) content. The Freundlich parameter n was significantly correlated with pH and amorphous iron oxides content, while 52% of its variance was explained by amorphous Fe and dithionite extrac‐table aluminum (Al). The P sorption maxima calculated from the Freundlich equation were in general lower than those calculated by the Langmuir equation. Both these parameters were strongly correlated with clay and more slightly with sesquioxides content. About 50% of their variance was explained by clay content of the soils. The P sorption index was strongly correlated with the clay content and less strongly with dithionite‐extractable Fe and Al. The P‐buffering capacity calculated from the data of Langmuir equation was also strongly correlated with these two parameters. In addition, clay content and dithionite‐extractable Fe and Al were well correlated to the amounts of P required to obtain an equilibrium concentration of 0.2 mg P/L while 61% of the variation of this parameter was explained by the clay and the dithionite‐extractable Fe content. From these findings, it seems that for the red Mediterranean soils from Greece, P sorption is affected by clay content and iron and aluminum oxide contents.  相似文献   

14.
Soil phosphorus (P) management requires a more targeted and soil‐specific approach than is currently applied for agronomic recommendations and environmental evaluation. Phosphorus buffering capacities control the supply of P in the soil solution and were measured across Irish soils with contrasting parent material and chemical properties. Langmuir sorption buffer capacities (MBCs) and binding energies (b) were strongly correlated with soil pH and extractable aluminium (Al). A broken‐line regression fitted to the relationship between MBC and Al derived a change‐point value for Al above which MBC increased linearly. Soils above the change point were predominantly acidic to neutral with non‐calcareous parent material, with larger buffering capacities and binding energies than calcareous soils. Ratios of Mehlich3‐Al and P (Al:P) were used to relate buffering capacity to supply potential in non‐calcareous soils. Large ratios of Al:P were associated with poor P availability, characteristic of strongly P‐fixing soils. Threshold values of iron‐oxide paper strip P (FeO‐P) and Morgan's P revealed Al:P ratios where soils began to supply P in available form. The change‐point for Morgan's P fell within the current target index for P availability; however, the confidence interval was more compatible with previous agronomic P indices used in Ireland. Relationships between Morgan's P and measures of extractable P, M3‐P and Olsen P, deviated in calcareous soils at large soil P contents, indicative of P precipitation processes dominating in these soils. Identifying differences in soil P buffering capacity at the laboratory scale would improve agronomic and environmental assessment at field and catchment scales.  相似文献   

15.
The Montserrat series is one of the most fertile of tropical soils. Substantial amounts of exchangeable K, available P, and favourable organic matter content and distribution contribute to its unique properties. P occurs in amounts ranging from 0.4 to 0.6 per cent, about 75 per cent of which is inorganic with Fe phosphates making up the bulk. Truog's reagent almost quantitatively extracts Ca phosphate and Bray's and Olsen's reagents extract mainly Al phosphate. Exchangeable K is derived from glauconite. High exchangeable Ca and Mg contents derived from weathering of carbonates impart a favourable pH to the soil for plant growth. Exceptional structural stability to 120 cm depth is associated with high free iron oxide, organic matter, and Ca contents. The outstanding feature in mineral weathering is the rapid transformation of glauconite through vermiculite to kaolinite and the formation of goethite. Considerable interlayering occurs between vermiculite with sesquioxide coatings and mica-vermiculite interlayers. Much of this weathering occurs in the calcareous, oxidized, friable parent rock. The features of the Montserrat series described above substantiate its classification as a Brown Earth (Mollisol).  相似文献   

16.
The adsorption of copper, zinc, and lead by two urban soils with different degrees of contamination was studied. Changes in the sorption capacity of the soils and the binding strength of the metals with the soil were determined after the removal of organic matter and iron minerals with a potassium pyrophosphate solution and Tamm’s reagent. The selectivity of these solutions for the dissolution of soil components was estimated.  相似文献   

17.
Geochemical sorption and biological demand control phosphorus (P) retention and availability in soils. Sorption and the biota predominantly utilize the same inorganic form of P, from the same soil pool, on the same time scale, and thus are likely to compete for P as it flows through the available pool. In tropical soils, P availability is typically quite low and soil geochemical reactivity can be quite high. We tested whether greater P sorption strength in tropical soils resulted in lower biological uptake of available P. Since the strength of soil sorption and biological demand for P change as ecosystems develop and soils age, we used soils from the two upper horizons from three sites along a 4.1 million-year-old tropical forest chronosequence in the Hawaiian archipelago. We evaluated the strength of geochemical sorption, microbial demand, and the partitioning of added available P into biological versus geochemical soil pools over 48 h using a 32PO4 tracer. Soil sorption strength was high and correlated with soil mineral content. The amount of added phosphate geochemically sorbed versus immobilized by microbes varied more between the organic and mineral soil horizons than among soil ages. Microbial activity was a good predictor of how much available P was partitioned into biological versus geochemical pools across all soils, while sorption capacity was not. This suggests that microbial demand was the predominant control over partitioning of available P despite changes in soil sorption strength.  相似文献   

18.
Peat samples representing depths of 0–15 cm and 15–30 cm were obtained from 11 upland sites in southern Scotland. Their pH, ash content, cation exchange capacity, phosphate sorption index and contents of 0.1 m hydrochloric acid-extractable iron and aluminium were determined as indicators of the extent to which phosphate and potassium ions would be retained following afforestation and application of fertilizers to these sites. In all soils cation exchange capacities were considerably larger than the quantity of potassium normally applied as fertilizer. Phosphate sorption indices were closely related to the content of extractable iron and aluminium in the peat samples. When expressed on a volume basis, the indices were low compared with those published for mineral soils, and some peats appeared to have almost no capacity to sorb phosphate ions from solution.  相似文献   

19.
MECHANISMS OF PHOSPHATE SORPTION BY SOILS AND HYDROUS FERRIC OXIDE GEL   总被引：5，自引：0，他引：5  
Data for the sorption of added inorganic phosphate (P) by contrasting soils and iron oxide gel were resolved by a method of successive approximation of the Langmuir sorption constants. Three distinct Langmuir equations described the overall isotherm irrespective of the experimental conditions used. Free energies of sorption (ΔG) for a particular region were similar for each soil and for iron oxide gel under all experimental conditions. In contrast, the sorption maximum for each region was influenced by the sorbent and experimental conditions. Because of the pronounced similarities in their P sorption characteristics iron oxide gel was used as a model surface for P sorption by soils. Three mechanisms for P sorption by iron oxide gel and by soils are proposed: (i) chemisorption at protonated surface sites, (ii) chemisorption by replacement of surface hydroxyls, and (iii) a more-physical sorption of P as a potential-determining ion.  相似文献   

20.
The sorption of zinc (Zn) by two acid tropical soils, Mazowe clay loam (kaolinitic, coarse, Rhodic Kandiustalf) and Bulawayo clay loam (coarse, kaolinitic, Lithic Rodustalf), was studied over a wide range of Zn solution concentrations. Samples of the two soils used in the experiments were collected at both uncleared, uncultivated (virgin) sites and cultivated sites. The two virgin soils showed similar abilities to bind Zn. Mazowe soil (40 g organic matter kg?1) presented the highest affinity for Zn. Yet, Bulawayo soil (23.5 g organic matter kg?1) sorbed almost the same amount. Bulawayo soil had higher pH and Fe and Mn-oxide content than Mazowe soil. Once cultivated, the two soils behaved quite differently. After 50 years, Mazowe soil had lost 60% of its organic matter and effective cation exchange capacity (ECEC). In this soil, Zn sorption capacity had also been decreased by 60%. Clearing and 10 years under cultivation had affected neither the organic matter content nor the ECEC of Bulawayo soil. For this soil, Zn sorption was even higher in the cultivated soil, presumably due to an increase in the amount of Fe and Mn oxide from subsoiling. Zinc sorption was dependent upon pH, with retention dramatically increasing in the pH range 6–7. Sorption occurred at pH values below the point of zero charge (PZC), indicating that the sorption reaction can proceed even in the presence of electrostatic repulsion between the positively charged soil surface and the cation. In the two soils, the reversibility of the sorption reaction was very low. More than 90% of the sorbed Zn was apparently strongly bonded.  相似文献   

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