Comparison of Phosphorus Determination Methods by Ion Chromatography and Molybdenum Blue Methods

The suppressed ion chromatography (IC) and molybdenum blue methods were used to comparatively evaluate phosphorus (P) concentrations. Most of the P was more resistant to hydrolysis in ion chromatography as compared to the molybdenum blue method. However, P analysis by IC is more liable to be interfered than the molybdenum blue method because of the presence of high bivalent and trivalent metal ions. Polyvalent metal ions interfere with organic P hydrolysis or the release of P from colloids during P investigation, which leads to a difference of ortho-phosphate concentrations determined by IC and molybdenum blue methods. During the environmental samples analysis, the ortho-phosphate obtained by the IC method was usually less than that obtained by the molybdenum blue method.     

Comparison of Methods for Amylose Screening Among Amylose‐Extender (ae) Maize Starches from Exotic Backgrounds

Breeding for high‐amylose corn requires a rapid analytical method for determining starch amylose so that generating wet chemistry values does not pose a major limitation in the volume of materials that can be screened. Two methods for determining apparent amylose content (AAC) were examined and compared with an iodine‐binding method involving the solubilization of isolated starch in a sodium hydroxide solution (method 1). These methods included one based on near‐infrared transmittance spectroscopy (NIRT) (method 2) and another iodine‐binding method involving the solubilizing of starch from ground whole corn with a DMSO‐iodine solution (method 3). These methods were chosen because, aside from initial set up costs, they are relatively rapid and inexpensive to perform. The materials evaluated consisted of various exotic corn populations including plant introductions and experimental materials generated from the Germplasm Enhancement of Maize (GEM) project. Crosses were made between these materials and a Corn Belt dent hybrid (OH43 × H99) converted with the amylose‐extender (ae) allele. Grain from F2 ears, presumed to be homozygous for the ae allele based on visual selection of mutant kernels on F1 ears from which they were planted, were then evaluated to identify possible modifiers of ae conditioning high starch AAC. From a total of 1,006 F2 ears, a core set consisting of 155 samples was established and only these were subjected to starch AAC analysis, using all three methods to compare the methods. Method 2 showed poor correlation to method 1 (r = 0.88), however, NIRT did appear to discriminate between samples converted to ae vs. those with a normal or possibly segregating endosperm type. Method 3 showed a slightly better correlation with method 1 (r = 0.92) and appeared to more fully discriminate among samples with AAC values >65% from those at ≈55%. Results from this study suggest that NIRT may be useful when a quick screening method is needed to discriminate mutant from nonmutant genotypes within grain samples of exotic germplasm especially when visual identification is difficult. In addition, method 3 could be used to replace the more time‐consuming method 1 when trying to identify high AAC levels among ae genotypes, even though some inconsistency was observed between the two methods. Finally, this study revealed that exotic germplasm may be an important source of new modifiers to the ae allele because values as high as 70% AAC were identified.     

Comparison of Two Methods for Determination of Soil Fixed Ammonium

Twenty-four soils were sampled from northwestern China to study the relations of fixed or nonexchangeable ammonium (NH₄) determined by the widely used Silva–Bremner method and the simplest ignition Mogilevkina method with organic matter (OM), total nitrogen (N), and soil particle composition. Results showed that the averaged values of 24 soils determined by the Silva–Bremner method were 10.7% greater than those using the Mogilevkina method, and the standard deviations of the Mogilevkina method were larger than those of the Silva–Bremner method. There was a close correlation in the fixed NH₄ between the two methods (R²?=?0.7831, n?=?24). The low values obtained by the Mogilevkina method were not due to the heat treatment because there was almost no difference in results between heating for 44 and 72 h. Soil OM had no correlation with the fixed NH₄ amounts determined by the two methods due to self-correlations, but total N had significantly weak correlations. The soils sampled from northwestern China were dominant in the 2:1 type of clay minerals, and significant correlations were found for the fixed NH₄ amounts determined by the two methods with clay as well as with clay plus silt contents. Correlations (R²) of the fixed NH₄ by the Silva–Bremner method were 0.4545 and 0.3145 with clay and clay plus silt contents, respectively, for the initial soils and 0.4765 and 0.446, respectively, for soils after ryegrass planting, which were much greater than those of the Mogilevkina method. Based on the definition of fixed NH₄ and the problem that occurred during its determination, two criteria were proposed for evaluation of the methods: (1) the relationship between clay content or clay plus silt contents and fixed NH₄ and (2) the correlation of OM content with fixed NH₄. By these criteria, the Silva–Bremner method was superior to the Mogilevkina method in terms of reliability and accuracy.     

Comparison of Methods for Determination of Carbon in Calcareous Soils

The global cycle of carbon (C) has raised attention in recent decades due to the great increase in carbon dioxide levels (CO₂) levels in the atmosphere and its influence on climate change. Calcareous soils represent a significant fraction of the areas with potential for agriculture and have differential attributes, such as high calcium contents, magnesium, carbonates, and pH values. These attributes have been ignored in analytical procedures despite these characteristics, resulting in an overestimation or underestimation of the soil carbon. Several methods have been proposed for determining the soil carbon contents, however, studies evaluating the analytical procedures of C quantification methods, considering the soil characteristics, such as the calcareous soils, are needed, in order to improve their accuracy. Therefore, the objective of this work was to evaluate and compare methods for C determination and to propose adjustments in the methodology for calcareous soil analysis. The Yeomans and Bremner (YB) was the most efficient method for quantification of organic C among the wet oxidation methods. On the other hand, the Donagemma (WB) method underestimated the organic carbon contents. The results showed that the samples must be macerated and pretreated with a hydrochloric acid solution for the use of CHNS-O, in order to eliminate carbonates in the form of nodules and concretions.     

Comparison of Colorimetric and ICP Methods of Phosphorus Determination in Soil Extracts

The traditional method for quantifying phosphorus (P) in Manitoba soil extracts is the molybdate blue–ascorbic acid colorimetric method. The shift from this traditional method to newer and more sophisticated analytical methods such as inductively coupled plasma (ICP) optical emission spectroscopy for P determination in soil extract could have serious implications on agronomic and environmental P management. Thus, the objectives of this study were to compare P determination by colorimetric and ICP methods in four extractants, namely Olsen, Mehlich 3, CaCl₂, and water extraction methods and to evaluate the possibility of developing conversion equations for P determination for the two methods in Manitoba soils. A laboratory experiment was conducted to establish relationships between P determination by colorimetric and ICP methods. Sixty surface soil samples (30 manured and 30 nonmanured) were collected from across Manitoba and extracted with Mehlich 3 reagent, Olsen solution, calcium chloride (CaCl₂) solution, and deionized water. Extractable P in the extract was determined by colorimetric (Col-P) and ICP (ICP-P) methods. The concentrations of P measured by the two methods were statistically analyzed. Mean comparison showed that P amounts determined by ICP in Mehlich 3, water, and CaCl₂ solutions were significantly greater than those determined by colorimetric method (P < 0.05) in the study. The differences between P determinations by the two analytical methods in the extractants were probably due to the presence of organic P, which was included in ICP determination but not in colorimetric determination. The influence of other factors such as the presence of colloidal particles on the P that was determined by the two methods could not be ruled out. However, Olsen P determined by the colorimetric method was not significantly different from the values determined by ICP (P > 0.05) probably because the alkaline nature of this extractant enhanced the hydrolysis of organic P in the extract, thus including organic P in the colorimetric determination of P. There were significant correlations between the two methods of P determination in the various extracting solutions with correlation coefficients ranging between 0.94 and 1.00. The two methods of P determination were linearly related for all the extracting solutions.     

Comparison of Various Analysis Methods for Determination of Iron Chlorosis in Apple Trees

Abstract

The objective of this study was to compare iron (Fe) concentrations (mg kg^?1) of the leaves measured by different methods and to determine the most suitable method to be used in evaluation of iron chlorosis in apple trees. For this purpose, green and chlorotic leaves were collected from 76 apple orchards in 1998 and 1999. Iron concentrations (mg kg^?1) of dried leaf samples were measured with 4 different methods, 1 N HCl (Method 1), 0.1 N HCl (Method 2), 0.005 M DTPA (Method 3), and 1.5% o-phenanthroline (Method 4). Total Fe concentrations (mg kg^?1) of dried leaf samples were also analyzed. Total chlorophyll and peroxidase enzyme activity in fresh leaf samples were measured. The total chlorophyll, peroxidase enzyme activity, Fe concentrations (mg kg^?1) determined by Method 1, Method 3, Method 4, and total Fe concentrations (mg kg^?1) of green leaves were higher than those of chlorotic leaves. On the other hand, no significant difference was found between Fe concentrations (mg kg^?1) of green and chlorotic leaves, measured with Method 2. Significant relationship observed amongst chlorophyll concentrations, peroxidase enzyme activity, and Fe concentrations (mg kg^?1) of samples suggests that 1 N HCl method was the most suitable method amongst the methods used in this study for apple trees.     

Determination of the Stability of MSW Compost Using a Respirometric Technique

This paper reports a fully automatic respirometric technique with low maintenance costs that allows the routine determination of the specific oxygen uptake rate (SOUR), as well as the cumulative oxygen demand at 20 h, (OD₂₀). The procedure involves the measurement of the dissolved oxygen concentration in an aqueous suspension of compost that is supplied with various nutrients, none of which contains organic carbon. The proposed method was used to monitor composting in a compost pile consisting of 65% organic matter obtained by selective collection of municipal solid waste (MSW), 30% sewage sludge and 5% plant trimming residues. Based on the results, the maximum SOUR value reached, (SOUR_max), decreases gradually with time, to values near 1 mgO₂/gVS.h after 130 days; indicating that the final product is stable. Linear correlations between OD₂₀ and the absorbances at 465 and 665 nm of aqueous extracts of compost, and its soluble chemical organic demand (COD_sol), and soluble organic carbon (TOC_sol) are significant at the p ≤ 0.01 level. However, the use of such variables instead of respirometric data requires prior experimentation with the type of waste to be composted in order to identify the absolute values at which biological activity ceases.     

Comparison of Chemical Extraction Methods for Determination of Soil Potassium in Different Soil Types

Determining potassium supply of soil plays an important role in intensive crop production, since it is the basis for balancing nutrients and issuing fertilizer recommendations for achieving high and stable yields within economic feasibility. The aim of this study was to compare the different extraction methods of soil potassium from arable horizon of different types of soils with ammonium lactate method (K_AL), which is frequently used as analytical method for determining the accessibility of nutrients and it is a common method used for issuing fertilizer recommendations in many Europe countries. In addition to the ammonium lactate method (K_AL, pH 3.75), potassium was extracted with ammonium acetate (K_AA, pH 7), ammonium acetate ethylenediaminetetraacetic acid (K_AAEDTA, pH 4.6), Bray (K_BRAY, pH 2.6) and with barium chloride (\(K_{BaCl_2 }\), pH 8.1). The analyzed soils were extremely heterogeneous with a wide range of determined values. Soil pH reaction \(\left( {pH_{H_2 O} } \right)\) ranged from 4.77 to 8.75, organic matter content ranged from 1.87 to 4.94% and clay content from 8.03 to 37.07%. In relation to K_AL method as the standard method, \(K_{BaCl_2 }\) method extracts 12.9% more on average of soil potassium, while in relation to standard method, on average K_AA extracts 5.3%, K_AAEDTA 10.3%, and K_BRAY 27.5% less of potassium. Comparison of analyzed extraction methods of potassium from the soil is of high precision, and most reliable comparison was K_AL method with K_AAEDTA, followed by a: K_AA, \(K_{BaCl_2 }\) and K_BRAY method. Extremely significant statistical correlation between different extractive methods for determining potassium in the soil indicates that any of the methods can be used to accurately predict the concentration of potassium in the soil, and that carried out research can be used to create prediction model for concentration of potassium based on different methods of extraction.     

Comparison of Various Chemical Extraction Methods used for Determination of the Available Iron Amounts of Calcareous Soils

This study was conducted to compare the most appropriate method for the evaluation of available iron (Fe) status of calcareous soils by using nine different chemical extraction methods. Leaf and soil samples were collected from nine peach (Prunus persica L.) orchards, each of which included green, slightly chlorotic, and severely chlorotic peach trees. According to the chlorosis degrees of the leaves, total and active Fe contents and some soil properties were determined. Relationships between these parameters and Fe amounts obtained from the methods were correlated. Among the methods tested, method 3 (M3) [0.05 N hydrochloric acid (HCl) + 0.025 N sulfuric acid (H₂SO₄)] and method 8 (M8) 0.05 M ethylenediaminetetraacetic acid (EDTA) (pH 7.0) were the most suitable methods to indicate the available Fe status of the soils.     

Comparison of Open Digestion Methods for the Determination of Rare Earth Elements in Plant Samples by ICP-MS

An analytical procedure for the reliable determination of rare earth elements (REEs) in plant samples by inductively coupled plasma-mass spectrometry (ICP-MS) was developed. The influence of the main matrix elements was investigated first. It was established that moderate amounts (0.1–1.0%) of dissolved solids decreased the REEs signals significantly. Internal standardization with indium proved to be useful for obtaining correct results. Various digestion procedures were next applied to converting various solid plant samples to aqueous solution, namely dry-ashing, dry-ashing including a hydrofluoric acid (HF) step, and wet digestion using hydrogen peroxide (H₂O₂) and nitric acid (HNO₃). Obtained results showed that the simple dry-ashing procedure was sufficient for plants. A certified reference material (BCR-670, aquatic plant) was used to validate the accuracy of the method. Relative standard deviations varied from 1% (holmium, gadolinium) to 4% (europium). Detection limits between 13 (lanthanum) and 0.02 ng L^?1 (lutetium) were achieved.     

A Comparative Study of Fourier Transform Raman and NIR Spectroscopic Methods for Assessment of Protein and Apparent Amylose in Rice

Fourier‐transform Raman (FT‐Raman) spectroscopy and near‐infrared (NIR) reflectance spectroscopy were used to compare calibration models for determining rice cooking quality parameters such as apparent amylose and protein. Samples from two seasons were used in each calibration set. The laboratory values ranged from 4.89 to 12.48% for protein and from 0.2 to 25.7% for amylose. The data for both FT‐Raman and NIR were preprocessed with orthogonal signal correction (OSC) for standardization. For both spectroscopic methods, five models were optimized by partial least squares regression (PLSR) and by Martens' uncertainty regression (MUR), including no processing, smoothing, normalization, first derivative (D1), and second derivative (D2). Based solely on standard error of cross‐validation (SECV), the FT‐Raman method was superior to the NIR method for protein. For amylose, the FT‐Raman and NIR methods resulted in similar calibration statistics with a high precision, with the FT‐Raman requiring fewer factors. The best FT‐Raman models were generated from OSC preprocessing with MUR for protein (SECV 0.15%, five factors) and from OSC without MUR for amylose (SECV 0.70%, seven factors). The best NIR models were obtained with D2 transform of OSC spectra for protein (SECV 0.22%, four factors) and with OSC spectra for amylose (SECV 0.57%, 11 factors).     

Determination of the Residual Metal Binding Characteristics of Soils Polluted by Cd and Pb

Four soils contaminated by Pb-Zn mining, Pb-Zn smelting, sewage sludge application, and clay pigeon shooting, respectively, were evaluated for their ability to attenuate relatively high concentrations of supplied Cd and Pb. The retention characteristics of the polluted soils and ‘background’-unpolluted soils for Cd and Pb, were assessed by batch adsorption experiments and equilibrium dialysis titration of the soil organic component. From the sorption data it was observed that the mining polluted and sewage sludge treated soils showed no significant change in Cd affinity when compared to the unpolluted soils. However, for Pb, the reduction in the slopes in the isotherms of the sludge treated and shot over soils were significant when compared to the background soils – indicating a reduced affinity for Pb. The Cd and Pb complexation capacities of the organic component were reduced in the mining, smelter and shot over soil compared to their respective background soils. However, the complexation capacity for Cd of the sludged soil increased from 1.01 µmol Cd g^-1 of organic matter to 4.38 µmol Cd g^-1 of organic compared to the background soil, but, the stability constant of the organo-metal complex formed was lower (6.05 cf. 6.85).     

Near‐Infrared Spectroscopy for Determination of Protein and Amylose in Rice Flour Through Use of Derivatives

The use of the derivative method for near‐infrared (NIR) calibration was investigated to determine protein and amylose content in rice flour. Samples for two years, 1996 and 1999, were combined to give a wide range of the constituents for development of the calibration model. The NIR spectral data were transformed with Savitzky‐Golay derivative with multiplicative scatter correction. To develop the best derivative models, the polynomial fits (quadratic, cubic, and quartic), convolution intervals (3–11 points for protein, 3–17 points for amylose), and derivative orders (1st derivative D1; 2nd derivative D2) were investigated. For the protein analysis, all polynomial fits with 3–11 points were acceptable to develop both the D1 and D2 models. However, the three‐point quadratic and five‐point quartic fits were not acceptable for the D1 model, and the three‐point quadratic fit was not acceptable for D2. For the amylose analysis, the D1 model produced generally better results than D2. Higher convolution intervals were required for the D2 model, whereas the D1 model was not affected by convolution intervals. A quadratic (or cubic) fit with 17‐point convolution interval was acceptable for the amylose D2 model, and the quadratic fit with 5–11 points and cubic (or quartic) fit with 7–17 points were suitable for the D1 model. Based on the standard error of cross‐validation (SECV), the calibration models developed using data for two years resulted in good precision with an SECV of 0.23% for protein using four factors and an SECV of 1.0% for amylose using 10 factors.     

西北石灰性土壤阳离子交换量测定方法比较

阳离子交换量是评价土壤保肥性能和缓冲性能的重要指标,也是改良土壤和合理施肥的重要依据之一。为了给西北石灰性土壤阳离子交换量的测定提供科学依据,通过平行性实验、标准物质检测、实际样品检测,分析比较了目前普遍采用的测定方法乙酸钙交换法和三氯化六氨合钴浸提-分光光度法的优劣。结果表明,2种分析方法均具有较好的精密度和准确度,均适合西北地区石灰性土壤阳离子交换量的测定。从测定结果来看,三氯化六氨合钴浸提-分光光度法的土壤阳离子交换量测定值略高于乙酸钙交换法,在实际样品检测中相对标准偏差介于3.47%～9.46%。但相比之下乙酸钙交换法具有试剂成本较低的优势,而三氯化六氨合钴浸提-分光光度法具有节省时间的优势,检测人员可根据实际情况灵活选择使用。     

双循环新格局下酒泉市现代农业发展对策

为保持酒泉农业农村经济的持续增长,对促进现代农业的转型升级提供参考。在分析酒泉市农业发展特点及存在问题的基础上,提出了建立新型农业经营产业联盟、延长经营产业链以构建特色农产品“经济圈”、补齐农业短板做大做强优势特色产业、建立标准化生产加工体系、加快农业品牌创建提升市场知名度和产品价值、多形式拓宽农业科技创新投融资渠道破解资金难题等发展建议。     

作物养分定量化模型原理及方法比较分析

本文比较分析了养分经验模型和动态模拟模型的原理和计算方法。比较典型的经验模型有肥料效应函数方程,目标产量法,以及基于土壤肥力指标的QUEFTS(QUantitative Evaluation of the Fertility of Trop ical Soils)养分模型等。经验模型的特点是简单易行,所需参数少,但模拟精度难免误差较大;动态模拟模型由于考虑到复杂因素对作物养分吸收的影响,以及植物营养的动态过程,更能反映的系统真实行为。然而,由于土壤养分运移和作物养分吸收过程的复杂性,目前除氮外,还很难做到其它养分的动态定量化模拟,这些都还有待于更深入的基础性研究。     

土壤团聚体稳定性评价方法比较

土壤团聚体稳定性是评价土壤结构和土壤物理形状的重要指标.对土壤团聚体分形维数、土壤团聚体平均重量直径和>0.25 mm团聚体含量3种土壤团聚体结构评价的方法进行了探讨.结果表明,分形维数与>0.25 mm团聚体的含量呈负相关性,但是平均重量直径与>0.25 mm团聚体的含量有正的相关性.这三种方法都能应用来评价土壤结构,但是分形维数不仅表示土壤结构,还能说明土壤水分和土壤其它的物理性质.因此,分形维数是评价土壤结构的较好的方法.     

塑性土壤破碎方法的比较

用改装的三轴剪切仪对拉伸、扭转、弯曲、直剪、切割和纯切割等基本加载方式进行了详细研究。结果表明,弯曲加载是需要最小力及最少能耗使塑性土壤破碎的一种有效的加载方式。     

甘薯不同氯离子测定方法的比较研究

采用加标回收率的方法,分析并比较了硝酸银滴定法、紫外分光光度法和自动电位滴定法测定甘薯(Ipomoea batatas L.)幼苗Cl-含量的结果,并初步探明不同甘薯品种地上部和根系C1-吸收和分布规律.结果表明:(1)硝酸银滴定法重复性差且难以判断滴定终点;紫外分光光度法测定Cl-回收率低(52.9％～81.4％),且受样品浸提液颜色影响;自动电位滴定法Cl-回收率为93.9％～105.5％,相对标准偏差(RSD)为0.6％～ 6.0％,该方法操作简单、重复性好且精确度高,因此是测定甘薯氯含量的最佳方法;(2)利用自动电位滴定法测定不同甘薯品种Cl-积累和分布,结果显示:甘薯幼苗地上部Cl-含量为0.067～0.096 mmol g-1DW,根系Cl-含量为0.038～0.087 mmol g-1 DW,品种间甘薯幼苗地上部和根系Cl-含量皆存在显著差异.不同品种向地上部转运Cl-选择性比率均大于1.0,表明Cl-向地上部聚集,以菜用型福薯7-6比率最高,紫心型徐紫20-1和浙紫1号次之,淀粉型泉薯9号最低.