Improving Sensitivity of Solution 31P NMR Analysis in Australian Xeralfs

Phosphorus-31 nuclear magnetic resonance (³¹P NMR) spectroscopy is widely used to identify and quantify phosphorus (P) forms in soil. This study aimed to determine whether narrowing the soil to extractant sodium hydroxide–ethylenediaminetetraacetic acid (NaOH-EDTA) ratio from 1:20 to values as low as 1:4 would improve sensitivity of solution ³¹P NMR spectroscopy without degrading resolution or quantitation. Four Australian soils were tested using four ratios. The narrowest ratio of 1:4 gave the best quality NMR spectra in terms of signal-to-noise ratio. Peak resolution was not degraded on narrowing the ratio. There was no clear effect of narrowing the extraction ratio on extraction efficiency or the distribution of signal among chemical shift regions (orthophosphate, monoester P, diester P, and pyrophosphate). We conclude that a ratio of 1:4 improved NMR analysis for these particular soils and should be considered for other soils, particularly low-P soils, where NMR sensitivity is limiting.     

不同浸提剂对几种典型土壤中重金属有效态的浸提效率研究

测定了7种浸提剂对3种类型土壤中重金属元素Cu、Pb、Cd的浸提量，分析了不同土壤类型条件下Cu、Pb、Cd元素间和不同元素下土壤间浸提率的相关性。结果表明，在7种浸提剂中，EDTA-2Na的浸提效率最高，是最适宜的浸提剂；同种土壤类型条件下，重庆紫壤、河南潮土中重金属Cu、Pb、Cd元素之间的浸提率呈现出浸提率变化相同的趋势。对于同种重金属而言，Cu、Pb在湖南红壤与重庆紫壤、重庆紫壤与河南潮土之间的浸提率呈现出浸提率变化相同的趋势。     

速冻草莓色素提取条件的研究

以速冻草莓为原料,研究提取草莓红色素的最佳提取条件。试验结果表明,色素的最佳提取条件为：料液比（质量浓度g／mL）为1：12,用1．5mol／LHCl和无水乙醇作混合溶液（体积比l：9）作提取剂,提取温度40℃,提取时间5h。     

土壤有效态镉与稻米镉污染风险广东案例研究

为了科学评估土壤镉(Cd)污染造成的稻米Cd超标风险,以广东省韶关市(酸性土壤)和汕头市(中性土壤)Cd污染稻田为研究对象,对土壤与稻米配对样品进行回归分析,比较了两种提取剂(CaCl₂和DTPA)对土壤Cd的提取能力以及对稻米Cd含量的反映能力,以探讨适用于不同pH土壤的有效态Cd提取方法,建立最佳稻米Cd累积预测模型,并推导出土壤有效态Cd的风险阈值。结果表明:CaCl₂提取剂对Cd的提取能力小于DTPA;两种提取剂对酸性土壤Cd的提取能力显著高于近中性土壤。与土壤全Cd相比,有效态Cd含量可更好地预测稻米Cd含量。CaCl₂提取剂适用于全部试验区的酸性、中性土壤;DTPA适用于汕头市中性土壤,但不适用于韶关市酸性土壤。利用CaCl₂-Cd进行线性方程拟合,得到了最佳的稻米Cd预测模型。韶关市的早稻、晚稻预测模型各包含20个水稻品种,其土壤CaCl₂-Cd阈值分别约为0.10 mg·kg^-1和0.05 mg·kg^-1。研究表明,基于CaCl₂-Cd的稻米Cd预测方法和阈值可指导广东省Cd污染稻田安全利用,并对其他酸性土Cd污染区具有参考意义。     

茶园土壤有效态镉的提取方法

为筛选出适合茶园土壤有效态镉提取的提取剂并对提取方法进行优化,采集云南省普洱市、浙江省丽水市及嵊州市共62份土壤样品及其对应的茶树新梢样品,分别比较了0.1 mol·L^-1CaCl₂、0.1 mol·L^-1HCl、1 mol·L^-1NH;OAc、1 mol·L^-1MgCl₂、0.005 mol·L^-1DTPA 5种提取剂的提取效果,并对提取剂浓度、土液比、提取时间和振荡频率4个因素进行对比优化。结果表明:不同提取剂的提取率依次为0.1 mol·L^-1HCl>1mol·L^-1MgCl₂>0.005 mol·L^-1DTPA>0.1mol·L^-1CaCl₂>1 mol·L^-1NH;OAc。不同提取剂提取的有效态镉含量与新梢镉含量的相关系数从高到低依次为1 mol·L^-1NH;OAc>0.1 mol·L^-1CaCl₂>0.1 mol·L^-1HCl>1 mol·L^-1MgCl₂>0.005 mol·L^-1DTPA。提取条件优化试验发现,提取剂浓度和提取时间对有效态镉提取率影响较大,振荡频率和土液比对有效态镉提取率影响较小。研究表明,以NH;OAc作为茶园土壤有效态镉提取剂,提取参数为提取剂浓度6 mol·L^-1、土液比1∶10、提取时间120 min、振荡频率180 r·min;时,提取效果最佳。     

印度酸性耕作土中总锰、铁以及可提取态锰、铁的水平、分布及其与土壤性质的关系研究

A total of 400 surface soil(0–15 cm) samples were collected from cultivated soils representing four soil series,namely,Hariharapur,Debatoli,Rajpora and Neeleswaram in Orissa,Jharkhand,Himachal Pradesh and Kerala states of India,respectively,and were analyzed to measure the contents of total and extractable Mn and Fe,to establish the relationship among total and extractable Mn and Fe and soil properties,and to characterize the spatial distribution pattern of Mn and Fe in some cultivated acid soils of India. The contents of total as well as extractable Mn and Fe varied widely with extractants and soil series. However,the amounts of Mn or Fe extracted by diethylene triamine penta-acetic acid(DTPA),Mehlich 1,Mehlich 3,0.1 mol L-1 HCl and ammonium bicarbonate DTPA(ABDTPA) were significantly correlated with each other(P 0.01). Based on the DTPA-extractable contents and the critical limits(2 mg Mn kg-1soil and 4.5 mg Fe kg-1 soil) published in the literature,Mn and Fe deficiencies were observed in 7%–23% and 1%–3% of the soil samples,respectively. The content of soil organic carbon(SOC) had greater influence on total and DTPA-extractable Fe than did soil pH. Geostatistical analysis revealed that total and DTPA-extractable Mn and Fe contents in the acid soils were influenced by soil pH,SOC content,and exchangeable cations like potassium,calcium and magnesium. Spatial distribution maps of total and DTPA-extractable Mn and Fe in soil indicated different distribution patterns.     

Development of a New Soil Extractant for Simultaneous Phosphorus,Ammonium, and Nitrate Analysis

Abstract

A new soil extractant (H³A) with the ability to extract NH₄, NO₃, and P from soil was developed and tested against 32 soils, which varied greatly in clay content, organic carbon (C), and soil pH. The extractant (H³A) eliminates the need for separate phosphorus (P) extractants for acid and calcareous soils and maintains the extract pH, on average, within one unit of the soil pH. The extractant is composed of organic root exudates, lithium citrate, and two synthetic chelators (DTPA, EDTA). The new soil extractant was tested against Mehlich 3, Olsen, and water for extractable P, and 1 M KCl and water‐extractable NH₄ and NO₂/NO₃. The pH of the extractant after adding soil, shaking, and filtration was measured for each soil sample (5 extractants×2 reps×32 soils=320 samples) and was shown to be highly influential on extractable P but has no effect on extractable NH₄ or NO₂/NO₃. H³A was highly correlated with soil‐extractable inorganic N (NH₄, NO₂/NO₃) from both water (r=0.98) and 1 M KCl (r=0.97), as well as being significantly correlated with water (r=0.71), Mehlich 3 (r=0.83), and Olsen (r=0.84) for extractable P.     

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。     

3种方法对不同土壤类型速效磷测定结果的影响

选取广东主要母质(玄武岩母质、花岗岩母质和三角洲冲积物)发育的水稻土经过不同磷肥量盆栽试验后的样品作为供试材料,设0.5 mm和2 mm两种粒径,分别采用Olsen、Bray-1和Mehlich-3等3种方法测定土壤中速效磷含量。结果表明:Bray-1法与Olsen法和Mehlich-3法保持在0.01水平下线性相关,而Mehlich-3法与Olsen法却无显著线性相关关系;各方法测定值的相对大小因土壤而异,主要表现在玄武岩母质发育的水稻土上,Mehlich-3-P小于Olsen-P,其他主要母质发育的水稻土Mehlich-3-P却均大于Olsen-P;Bray-1-P为Mehlich-3-P的3～7倍不等,为Olsen-P的3～10倍不等,Mehlich-3-P为Olsen-P的2/3～3倍不等;土壤制样粒径对测定结果的影响不显著。     

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.