土壤有效态钒的浸提剂和浸提条件研究

采用盆栽实验及石墨炉原子吸收光谱法测定,比较了HOAc、MgCl2、NH4OAc、EDTA和EDTA-NH4OAc等5种浸提剂在不同提取时间、不同土液比下对土壤中有效态钒的提取效果。实验表明,不同浸提剂对土壤有效态钒的提取率明显不同,提取率均随土壤钒含量的升高而升高。浸提剂对土壤有效钒的提取率顺序依次为HOAcMgCl2NH4OAcNH4OAc-EDTAEDTA,其中0.05 mol L-1 EDTA的浸提效率最高,最大提取率61.1%。最佳提取条件为:平衡时间60 min、土液比1∶10。将拟定的提取方法用于玉米盆栽土壤中有效态钒的提取,土壤中有效态钒量与玉米根、茎叶中钒含量存在极显著的相关性,相关系数达0.9742和0.9497,故EDTA提取的有效态钒能很好地用于评价土壤中钒的植物可利用性。     

不同浸提剂对海南稻田土壤有效硒浸提效果比较

在海南定安县采集硒(Se)含量水平不同的3个代表性稻田土壤,结合水稻幼苗盆栽试验与黑麦草幼苗培养试验,用H2O(pH4.5)、0.5mol/LNaHCO3(pH8.5)和0.1mol/LKH2PO4三种浸提剂进行海南稻田土壤有效Se浸提效果的比较研究。结果表明:3种浸提剂提取的有效Se与植株累积的Se都呈极显著正相关,但H2O的提取能力弱。在水稻幼苗试验中,0.1mol/LKH2PO4与0.5mol/LNaHCO3相比,浸提时间短,测定的土壤有效Se的平均变异系数较小,且与水稻植株累积Se的相关系数较大,因此海南稻田土壤有效Se测定宜选0.1mol/LKH2PO4。     

酸性土壤有效汞提取方法研究

为了更好地评价酸性土壤中汞的生物有效性和生态风险,以酸性土壤为供试土壤,通过比较国内外几种常用的土壤有效汞的浸提剂的提取效果,筛选适合于酸性土壤的有效汞浸提剂并优化相应的提取条件,从而建立酸性土壤有效汞的提取方法。结果表明,在0.1 mol·L-1HCl、1 mol·L-1NH4OAc、0.005 mol·L-1DTPA、0.03%TGA-1/15 mol·L-1Na2HPO4这4种常用浸提剂中,0.03%TGA-1/15 mol·L-1Na2HPO4是最佳的浸提剂,因为它具有最高的提取率,且其所提取的有效汞与相应稻米中Hg含量的相关性最好。0.03%TGA-1/15 mol·L-1Na2HPO4的最佳浸提条件为土液比1∶10、振荡时间120 min、振荡速度250 r.min-1,浸提出的有效汞量与油菜的相关性达到极显著相关,能较好地指示田间条件下土壤汞对作物的可给性。     

稻菜轮作制下土壤有效态汞提取剂和提取条件研究

选择长三角地区代表性人为耕作土——青紫泥为研究对象,通过网室盆栽和室内试验,选用CaCl2,HCl,DTPA(二乙烯三胺五乙酸)和NH4OAc共4种提取剂,研究了水稻—小白菜—萝卜作物轮作系统中土壤有效态汞提取剂的选择与提取条件的优化问题。结果表明,不同提取剂提取的有效态汞含量随提取时间的延长而逐渐增加,30min可作为提取剂提取土壤有效态汞的最佳平衡时间;随土水比的减小,提取剂提取的土壤有效态汞量明显提高,1∶5为较适宜的土水比;不同提取剂的提取能力不同,对供试土壤,提取剂提取能力的大小顺序为:CaCl2>HCl>NH4OAc>DTPA。提取剂提取的土壤有效态汞量之间存在显著正相关,其中CaCl2和NH4OAc之间相关性最高;在土壤—水稻系统和土壤—萝卜系统中作物可食部位汞含量与提取剂提取的土壤有效态汞含量之间存在显著正相关关系,但在土壤—小白菜系统中相关性不强。综合分析,确定CaCl2为供试土壤汞有效态的最佳化学提取剂。     

黑土中有效态镍提取方法的选择

供试7种提取剂的最佳提取条件是:提取温度均为(25±1)℃;提取时间为DTPA 2 h,醋酸铵30 min,其余5种提取试剂60 min;提取时的土液比为蒸馏水和DTPA 1∶2,醋酸铵1∶10,其余4种提取试剂1∶5。DTPA作为提取剂时,盆栽作物的吸镍量与有效镍提取量之间的相关性达到极显著水平,并好于其它试剂。DTPA和EDTA作为提取剂时,有效镍提取量与植株干物重之间均达极显著的负相关,且相关系数高于其他试剂。考虑到用DTPA作提取剂时,可以同时测定铜、锌、铁、锰多种金属元素,因此黑土中有效态镍的最佳提取试剂是DTPA,最佳提取条件为:温度(25±1)℃、土液比1∶2、180次min-1往复振荡提取2 h。     

几种萃取剂对土壤中重金属生物有效部分的萃取效果

采用6种萃取剂：pH=7的0.01mol/L CaCl2、pH＝7.3的0.005mol/L DTPA 0.1mol/L TEA(三乙醇胺）＋0.01mol/L CaCl2、0.1mol/L NaNO3、0.43mol/L HOAc、pH=7的0.05mol/L EDTA和pH=4.65的0.5mol/L NH4OAc 0.01mol/L EDTA浸取液，对污染土壤中的重金属Cu、Zn、Cd、Pb的进行了萃取，并比较了萃取剂的萃取能力。实验结果表明，HOAc、EDTA以及NH4OAc－EDTA萃取各种重金属的能力远远大于其它几种萃取剂的萃取能力，是比较理想的萃取剂。     

AB-DTPA,CaCl_2-DTPA两种方法分析土壤8种元素的有效态含量

采用AB-DTPA浸提剂和电感耦合等离子体发射光谱法分析测定了上海土壤样品中8种元素的有效态含量,并与CaCl2-DTPA法比较,结果显示:AB-DTPA法分析土壤Cu、Zn、Mg、Ni、S、Cr、Mo和As 8种元素的有效态含量均高于CaCl2-DTPA法;其中AB-DTPA法测定Cu、Zn、Mg、Ni、S、Cr、Mo 7种元素的有效态含量与CaCl2-DTPA法均达到极显著相关;而AB-DTPA,CaCl2-DTPA两方法测定土壤有效态的As几乎不相关。结果表明:AB-DTPA法对这8种元素有效态的浸提率高于CaCl2-DTPA法,而两者的分析结果大多相关性好,由此可见,AB-DTPA法更适用于土壤此8元素有效态含量的分析测定。表8,参16。     

几种浸提剂对土壤有效硫测定的相关性探讨

采用4种浸提剂(CaCl2、Ca(HzPO4)2(pH=4．0)、KH2PO4、NaHC03(pH＝8．5))，对来自我国不同区域的7种土壤样品及北京近郊昌平平西府中科院遗传所试验基地冬小麦不同生育期麦田土壤进行了土壤有效S的浸提，同时对不同区域土壤的有效S、全S和小麦不同生育期植株的含S量进行了测定。结果表明，在土壤有效S与植株含S量的相关性中，4种方法都达到显著或极显著的水平。采用电感辊合等离子体原于发射光谱法(ICP—AES)和BaS04比浊法对Ca(H2PO4)2浸提的土壤有效S进行测定，二者的结果具有极显著的相关性，r值达0．867^**。二者测定的土壤有效S与植株含S量的相关性也达到了极显著水平，r值分别为0．794^**和0．684^**，说明了两种方法都适用于对土壤有效S的测定，但ICP—AES法的结果相对更稳定。4种浸提剂测定重复结果间的变异系数以Ca(H2PO4)2平均最小，只有5．3％，NaHC03最高，达8．3％。根据浸提剂的性质、土壤有效S与小麦植株含S量的相关性、测定结果重复间的变异系数得出，Ca(H2PO4)2浸提与离子色谱测定是判定土壤有效S最稳定的一种方法。     

Bowman-Cole石灰性土壤有机磷分组法的改进

本文研究了Bowman-Cole土壤有机磷分组法应用于石灰性土壤存在的若干问题,并提出了改进法。改进法的四组土壤有机磷(P0)的分组为:在氯仿预处理土样后用0.5molL-1NaHCO3浸提活性P0;然后,先用0.05molL-1NaOH、后用1molL-1H2SO4处理残余土样浸提中度活性P0,0.05molL-1NaOH提取的无机磷和1molL-1H2SO4提取的有机磷属于中度活性P0;在氯仿和0.5molL-1NaHCO3处理后,用0.05molL-1NaOH浸提稳定性P0,把浸提液的酸度调至pH3.00时,上清液中的有机磷为中度稳定性P0,而沉淀中的有机磷为高稳性P0。结果表明,改进法能更好地区分具有不同矿化率的有机磷化合物,例如,核酸、甘油磷酸、植酸钙、肌醇三磷酸铁、植酸铁等。改进法增加了超声波处理,使震荡时间也明显缩短。因此,石灰性土壤有机磷分组的改进法比Bowman-Cole法更理想。     

新鲜土样和改进ASI浸提剂对土壤有效养分测试的影响

通过分析基于风干土样和新鲜土样、ASI（Agro Services International Inc., ASI）浸提剂和改进ASI浸提剂进行测量的土壤有效养分含量的相关性,探索一种基于新鲜土样和联合浸提剂进行土壤有效养分测试的方法。结果表明,利用ASI浸提剂测量的北京潮土新鲜土样的NO3--N和NH4+-N、有效P、K、Ca、Mg、Cu、Fe、Mn、Zn、有机质含量、及pH值,与风干土样的测量值均呈显著的线性相关关系,经该线性方程回归检验的测量相对误差小于5%～9%;利用改进ASI浸提剂测量的新鲜土样和风干土样的NH4+-N、有效P、K、Ca、Mg、Cu、Fe、Mn、Zn含量与基于ASI浸提剂测量的也呈显著的线性相关关系,经该线性方程回归检验的测量相对误差小于5%～8%。因此,基于新鲜土样和改进ASI浸提剂测量石灰性土壤有效养分含量是可行的,可为车载式土壤养分检测提供一种快捷的土样浸提前处理方法。     

Prediction of Soil Cadmium Bioavailability to Cacao (Theobroma cacao L.) using Single-Step Extraction Procedures

In this study, complexation extractants ammonium bicarbonate diethylene triamine pentaacetic acid (AB-DTPA), diethylene triamine pentaacetic acid (DTPA), and ethylene diamine tetraacetic acid (EDTA) and mild cation-exchange extractants calcium chloride (CaCl₂) and ammonium nitrate (NH₄NO₃) were used to evaluate the bioavailability of soil cadmium (Cd) to cacao in the field. Among the five extractants, the extractable Cd generally followed the order EDTA > DTPA > AB-DTPA > CaCl₂ > NH₄NO₃. Correlation analysis was done between the extractable Cd in soil and total Cd content of cacao tissues (nibs, shells, leaves, and pods). The Cd extracted by CaCl₂ and NH₄NO₃ was significantly (P < 0.05) correlated with some of the tissues but their Pearson correlation coefficients were weak. In contrast, extractants AB-DTPA, DTPA, and EDTA showed stronger, significant correlations to the Cd concentration in all four tissues. Overall, regression analysis demonstrated that AB-DTPA, DTPA, or EDTA can be used to predict bioavailable Cd in soils for cacao. Of these, AB-DTPA and DTPA both showed the strongest correlations compared to EDTA. However, the ease of preparation and the superior shelf-life of DTPA over AB-DPTA make it the preferred reagent for Cd bioavailability extractions from cacao soils and is currently being used to develop cost-effective soil treatments to reduce bioavailable Cd to cacao plants.     

Determination of suitable chemical extraction methods for available zinc content of paddy soils at Thrace Region

This research was carried out in order to determine the zinc status of the paddy soils with different physical and chemical properties of Thrace region as well as to determine the most suitable method for chemical extraction of available zinc content of soils for plant. As a result of the investigation with 12 paddy soils representing the region, it was estimated that the application of increasing amounts of zinc to the soil of pot grown maize to increasing the zinc uptake, dry matter and zinc content of the plant was determined. Nine chemical extraction methods for available zinc contents of soil were used and the reliability of the investigated methods was ranked as: 0.005 r M DTPA+0.01 r M CaCl 2 +0.1 r M TEA; 0.005 r M DTPA+1 r M NH 4 HCO 3 ; 0.01 r M Na 2 EDTA+1 r M (NH 4 ) 2 CO 3 ; 0.01 r N Na 2 EDTA+1 r N NH 4 Oac; 0.01 r N Na 2 EDTA; 1 r N NH 4 Oac; 2 r N MgCl 2 ; 0.05 r N HCl+0.025 r N H 2 SO 4 ; 0.01 r M Hidrocinon. The method for extraction with 0.005 r M DTPA+0.01 r M CaCl 2 +0.01 r M TEA solution which not only owns the highest correlation coefficient but also enables determination of Fe, Mn and Cu concentrations in addition to Zn amount, could be recommended as the most suitable one for the investigated soils.     

Evaluation of Some Chelates in Estimating Available Zn for Soybean in Calcareous Soils

Six fertilizer trials on calcareous soils in Saudi Arabia were conducted for the prediction of Zn deficiency in soybean (Glycine max L., var Merr). Zinc level before planting was tested by using 3 different extractants, i.e. DTPA, AB-DTPA and EDTA. Zinc was applied in the form of ZnSO₄ · 7H₂O at 0, 5, 10, 15, 20 and 40 kg Zn ha^?1. Plant samples were taken at early bloom and tissue was analysed for Zn. Two methods were used to judge the critical deficiency level of Zn: Cate-Nelson and chisquare models. The critical level estimated according to the Cate-Nelson method for DTPA extractable soil Zn was 0.43 mg kg^?1 in the growing season 1991. EDTA gave a much higher level (1.80 mg kg^?1) and AB-DTPA gave an intermediate level (0.68 mg kg^?1). Chi-square statistical procedure gave a very similar critical level of 0.66 mg kg^?1 for AB-DTPA but lower for either DTPA (0.38 mg kg^?1) or EDTA (1.32 mg kg^?1). The critical level based for three growing seasons ranged from 0.25 to 0.68, 0.32 to 0.82 and 1.12 to 3.4 mg Zn kg^?1 for DTPA, AB-DTPA and EDTA extractants, respectively. The values obtained by the linear regression equation with soybean leaf concentration were 0.45 and 0.70 mg Zn kg^?1 for DTPA and AB-DTPA, respectively. Such values are very close to those determined by using the Cate-Nelson method. On the other hand, the value obtained for EDTA (1.15 mg Zn kg^?1) was comparatively lower than that calculated by applying the Cate-Nelson method.     

Soil Test to Predict the Copper Availability in Pasture Soils

Abstract

The proportion of copper (Cu) that can be extracted by soil test extractants varied with the soil matrix. The plant‐available forms of Cu and the efficiency of various soil test extractants [(0.01 M Ca(NO₃)₂, 0.1 M NaNO₃, 0.01 M CaCl₂, 1.0 M NH₄NO₃, 0.1 M HCl, 0.02 M SrCl₂, Mehlich‐1 (M1), Mehlich‐3 (M3), and TEA‐DTPA.)] to predict the availability of Cu for two contrasting pasture soils were treated with two sources of Cu fertilizers (CuSO₄ and CuO). The efficiency of various chemical reagents in extracting the Cu from the soil followed this order: TEA‐DTPA>Mehlich‐3>Mehlich‐1>0.02 M SrCl₂>0.1 M HCl>1.0 M NH₄NO₃>0.01 M CaCl₂>0.1 M NaNO₃>0.01 M Ca(NO₃)₂. The ratios of exchangeable: organic: oxide bound: residual forms of Cu in M1, M3, and TEA‐DTPA for the Manawatu soil are 1:20:25:4, 1:14:8:2, and 1:56:35:8, respectively, and for the Ngamoka soil are 1:14:6:4, 1:9:5:2, and 1:55:26:17, respectively. The ratios of different forms of Cu suggest that the Cu is residing mainly in the organic form, and it decreases in the order: organic>oxide>residual>exchangeable. There was a highly significant relationship between the concentrations of Cu extracted by the three soil test extractants. The determination of the coefficients obtained from the regression relationship between the amounts of Cu extracted by M1, M3, and TEA‐DTPA reagents suggests that the behavior of extractants was similar. But M3 demonstrated a greater increase of Cu from the exchangeable form and organic complexes due to the dual activity of EDTA and acids for the different fractions and is best suited for predicting the available Cu in pasture soils.     

Evaluation of universal extractants for determining plant available potassium in intensively cultivated soils

Abstract

Eighteen soils from northwestern Switzerland were used to study the value of seven universal extractants (CaCl₂; DB‐DTPA; Mehlich 1, 2, and 3; Morgan‐Wolf; and NH₄OAc‐EDTA) for predicting plant available potassium (K) as compared to a bioassay (a modified Neubauer test with winter rye). These extractants were evaluated on the basis of K uptake by the bioassay test and the soil K status. In order to create the sufficiency level of exchangeable K for plant growth, soils were treated with 0, 20, 40, 80, and 160 mg K/kg of soil. The range of K uptake by the bioassay tests was between 89.2 and 403.0 mg/kg of soil for the control pots, and 136.6 to 495.8 for the K treatments with optimal conditions for plant growth. The average amounts of K extracted by the seven universal extractants, in ascending order, were: CaCl₂ < Morgan‐Wolf < Mehlich 1 < Mehlich 2 < NH₄OAc‐EDTA < Mehlich 3 < DB‐DTPA. The highest simple correlation with K uptake versus the bioassay test was obtained with the DB‐DTPA (r = 0.89) extractant and the lowest with the Mehlich 1 (r = 0.53) extractant. The DP‐DTPA, NH₄OAc‐EDTA and Mehlich 3‐K procedures showed an advantage over K procedures based on water soluble and exchangeable K pools in the investigated soils in order to predict the amount of plant‐available K. A simple regression and the Cate‐Nelson graphic method offer the possibility of assessing the soil‐K status using K values obtained by these universal extractants and to calibrate them against K forms as follows: exchangeable, water soluble, and non‐exchangeable.     

Comparison of Mehlich-3 and Ammonium Bicarbonate-DTPA for the Extraction of Phosphorus and Potassium in Calcareous Soils from Florida

Developing a fast and reliable soil testing method is critical for improving soil testing efficiency and ensuring reliable fertilizer recommendation. The objectives of this study were to evaluate Mehlich-3 (M-3) as a replacement for ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA) to extract phosphorus (P) and potassium (K) and to determinate the relationships between extractable P and K and their uptakes by crop in calcareous soils. M-3 and AB-DTPA were compared by using two approaches. In the first approach, the amounts of extracted P and K were compared by analyzing soil samples collected from agricultural production areas; in the second approach, snap beans (Phaseolus vulgaris) were grown in pot to determine the P and K uptakes by crop. There were significant correlations between M-3 and AB-DTPA for both soil test P and K based on soils collected from the agricultural field and the pot study. Soil test P and K by both extractants were significantly correlated with their uptakes by snap bean. The critical value of M-3-P regarding snap bean uptake was 47 mg kg^?1 and was higher than that (18 mg kg^?1) for AB-DTPA-P, whereas critical soil test K levels were similar between M-3 and AB-DTPA. M-3 was identified as an alternate improved extraction method instead of AB-DTPA in calcareous soils based on this study. However, more work will be needed to identify the correlation of the two extractants and crop responses under a field condition.     

Determination of suitable chemical extraction methods for the available iron content of brown forest soils in Turkey

The aim of this research was to determine the available iron (Fe) content of brown forest soils of Edirne Province and the most suitable chemical extraction method. Eight chemical extraction methods (the 0.005 M DTPA + 0.01 M CaCl2 + 0.1 MTEA, 0.05 M HCl + 0.012 M H2SO4, 1 M NH4OAc (pH: 4.8), 0.01 M EDTA + 1 M NH4OAc, 1 M MgCl2, 0.01 M EDTA + 1 M (NH4)2CO3, 0.005 M DTPA + 1 M NH4HCO3, and 0.001 M EDDHA methods) and six biological indices (the dry matter yield, Fe concentration, Fe uptake, relative dry matter yield, relative Fe concentration, and relative Fe uptake) were compared. The biological indices were determined with barley (Hordeum vulgare L.) grown under greenhouse conditions. At the end of the experiment, the highest correlation coefficients (r) were determined to be between the 0.005 M DTPA + 0.01 M CaCl2 + 0.1 M TEA method and the biological indices and between the 0.005 M DTPA + 1 M NH4HCO3 method and the biological indices. The corresponding correlation coefficients (r) for the 0.005 M DTPA + 0.01 M CaCl2 + 0.1 M TEA method and the six biological indices were 0.621**, 0.823**, 0.810** 0.433**, 0.558**, and 0.640**, respectively. For the 0.005 M DTPA + 1 M NH4HCO3 method, these coefficients were equal to 0.618**, 0.520**, 0.679**, 0.521**, 0.492**, and 0.641**, respectively (** indicate the validity of the relationships at p < 0.01) These extraction methods, out of all the methods tested, were suggested for the determination of the available Fe content of the brown forest soils. Published in Russian in Pochvovedenie, 2006, No. 9, pp. 1068–1074. The text was submitted by the author in English.     

Zinc and copper in some soils of Egypt as related to other soil properties

Total Zn in alluvial and calcareous soils (average 138 and 70 ppm respectively) was significantly related to their contents of CaCO₃ (negatively), O.M. and clay (positively). Extracting Zn by Na₂EDTA gave the highest values for both soil types. Total Cu contents varied widely from 26 to 111 ppm in alluvial and from 15 to 30 ppm in calcareous soils. They were negatively correlated with the CaCO₃ contents. The pot experiments showed that EDTA(NH₄)₂CO₃, Na₂EDTA and DTPA are reasonable extractants for available Zn from both soil types. DTPA was efficient for all soils investigated, while Na₂ EDTA and EDTA-citrate were specific for extracting Cu from calcareous soils.