Determination of Fatty Acid Composition of Turfgrass by High‐Performance Liquid Chromatography

Abstract

The fatty acid composition of warm‐season turfgrasses is physiologically regulated by environmental changes, particularly temperature. Species or cultivars, which have increased degree of unsaturation, usually have a greater freeze resistance. Quantifying fatty acid composition not only can help understand the freeze‐resistant mechanism of warm‐season turfgrasses but also in practice develop a management strategy for better turf. A high‐performance liquid chromatography (HPLC) method was developed for this purpose. The method is based on the bromophenacyl reaction of fatty acids and separation on a C8 column with gradient elution. Information on limit of identification, linearity of quantification, response factor, and derivatization conditions is presented and discussed. The method presented is simple to apply and provides an alternative to the traditional gas chromatography (GC) method. The results of fatty acid composition from a field freezing‐resistance experiment are discussed.     

Re‐analysis of the Relationship between Organic Carbon and Loss‐on‐Ignition in Soil

The suitability of loss‐on‐ignition (LOI) as an alternative to direct measurement of organic carbon (OC) has been debated for decades without resolution. The literature contains an abundance of different linear regression models to describe the LOI–OC relationship, most based on untransformed values of LOI and OC. Such regression is suspect because the variables are unable to occupy Euclidean space. Logratio transformation—based on relative rather than absolute differences—eliminates this constraint. Re‐analysis of the relationship on new and 10 previously published datasets using logratio techniques reveals that the relationship is nonlinear and that the profusion of regression models is in part a function of the range of LOI. Although LOI may offer a crude estimate of OC at high LOI levels, OC/LOI ratios when LOI is less than about 25% are too variable for reliable OC estimation, and interstudy comparisons remain dubious. Direct measurement of OC is recommended.     

Loss‐on‐Ignition Method to Assess Soil Organic Carbon in Calcareous Everglades Wetlands

Measurement of soil carbon (C) is important for determining the effects of Everglades restoration projects on C cycling and transformations. Accurate measurement of soil organic C by automated carbon–nitrogen–sulfur (CNS) analysis may be confounded by the presence of calcium carbonate (CaCO₃) in Everglades wetlands. The objectives of this study were to compare a loss‐on‐ignition (LOI) method with CNS analysis for assessment of soil C across a diverse group of calcareous Everglades wetlands. More than 3168 samples were taken from three soil depths (floc, 0–10, 10–30 cm) in 14 wetlands and analyzed for LOI, total C, and total calcium (Ca). The LOI method compared favorably to CNS analysis for LOI contents ranging from 0 to 1000 g kg^?1 and for soil total Ca levels from 0 to 500 g Ca kg^?1. For all wetlands and soil depths, LOI was significantly related to total C (r² = 0.957). However, LOI was a better predictor of total C when LOI exceeded 400 g kg^?1 because of less interference by CaCO₃. Total C measurement by CNS analysis was problematic in soils with high total Ca and low LOI, as the presence of CaCO₃ confounded C analysis for LOI less than 400 g kg^?1. Inclusion of total Ca in regression models with LOI significantly improved the prediction of total C. Estimates of total organic C by CNS analysis were obtained by accounting for C associated with CaCO₃ by calculation, with results being similar to total organic C values obtained from LOI analysis. The proportion of C in organic matter measured by the LOI method (51%) was accurate and applicable across wetlands, soil depths, and total Ca levels; thus LOI was a suitable indicator of total organic C in Everglades wetlands.     

Landscape and Land‐Use Effects on the Spatial Variation of Soil Chemical Properties

The current study addressed the spatial variation of soil organic matter (SOM), total nitrogen (TN), extractable phosphorus (EP), and extractable potassium (EK) in agricultural soils of a representative region, northeast China. Soil cation exchange capacity (CEC) and the effects of landscape attributes and land use were also investigated. The techniques used included conventional statistics, geostatistics, and geographic information systems (GIS). Our study demonstrated that EP had the greatest coefficient of variation (CV), and CEC had the least CV. The experimental semivariograms of the five soil chemical properties included in this study were all fitted with exponential models. The five soil variables all showed moderate spatial dependence. The SOM, EK, and CEC decreased with increasing altitude. Significant negative relationships were found between the slope gradient and EP, EK, and CEC. Relatively steeper slopes might result in greater soil erosion, which leads to a decline in soil nutrients. Soil types had significant impacts on all soil chemical properties, which reflect the effect of the parent soil material. In general, the mean values of soil variables for vegetable land were statistically greater than those for upland and paddy fields. After being divided into two parts along the Yinma River, soil samples of the western part have statistically greater SOM, EP, EK, and CEC values than those collected from the eastern part.     

Influence of Soil Moisture on Root Colonization of Glyphosate‐Treated Soybean by Fusarium Species

Abstract

The widespread use of glyphosate‐resistant (GR) cropping systems may impact rhizosphere microbial associations and crop productivity. It was previously reported that glyphosate accumulation in the rhizosphere may stimulate colonization of soybean [Glycine max (L.) Merr.] roots by soilborne Fusarium. Field studies often reveal inconsistent root colonization by Fusarium, especially during growing seasons characterized by contrasting rainfall patterns. Therefore, this study was conducted to determine the impact of different soil moisture contents on root colonization of glyphosate‐treated soybean by Fusarium species. Glyphosate (0.84 kg ae ha^?1) was applied to greenhouse‐grown glyphosate‐resistant (GR) soybean at the two to three trifoliate-leaf (V2–V3) growth stage growing in a Mexico silt loam at 27%, 13%, and 10% soil moisture contents. Soil and plant samples were sampled periodically after herbicide application and selectively cultured for Fusarium. Highest Fusarium colonization was associated with the glyphosate treatment, with maximum levels occurring at the highest soil moisture level. Thus, glyphosate interactions with root colonization by Fusarium in glyphosate‐resistant soybean are greatly influenced by soil moisture content.     

Effects of water‐soluble constituents of plant residues on water uptake by seeds

Abstract

There has been strong support for the hypothesis that the adverse effects of plant residues on crop yields are due to phytotoxic compounds derived from these residues. This hypothesis is based largely on studies showing that, when compared with distilled water, aqueous extracts of plant residues have an adverse effect on seed germination and seedling growth. Because seed germination and seedling growth are reduced by a delay in germination resulting from slow uptake of water by seeds, we studied the possibility that the adverse effects of aqueous extracts of plant residues on seed germination and seedling growth might be at least partly due to water uptake by seeds being retarded by water‐soluble constituents of these residues. To test this possibility, we compared the rates of water uptake and germination of seeds of corn (Zea mays L.), soybean [Glycine max. (L.) Merrill], and wheat (Triticum aestivum L.) when these seeds were treated with distilled water and with aqueous extracts of corn, sorghum [Sorghum bicolor (L.) Moench], and wheat residues. We found that the rates of water uptake and germination of seeds treated with aqueous extracts of plant residues were appreciably slower than the corresponding rates for seeds treated with distilled water. This may be due to the water potentials of these extracts (ca. ‐50 kPa) because when seeds of corn, sorghum, and wheat were treated with a solution of polyethylene glycol 8000 having a water potential similar to that of the extracts of plant residues tested, the rates of water uptake and germination were also slower than the corresponding rates for seeds treated with distilled water. These observations suggest that the adverse effects of aqueous extracts of plant residues on seed germination and seedling growth when compared with distilled water may be partly due to constituents of these extracts inducing water potential effects that reduce water uptake by germinating seeds.     

Tillage Effects on Soil Quality Indicators and Nematode Abundance in Loessial Soil under Long‐Term No‐Till Production

Abstract: Soil quality indicators and nematode abundance were characterized in a loessial soil under long‐term conservation tillage to evaluate the effects of no‐till, double‐disk, chisel, and moldboard plow treatments. Indicators included soil electrical conductivity (EC), soil texture, soil organic matter (SOM), and total particulate organic matter (tPOM). Nematode abundance was positively correlated with EC, silt content, and total POM and negatively correlated with clay content. Clay content was the main source of variation among soil quality indicators and was negatively correlated with nematode abundance and most indicators. The gain in SOM in the no‐till system amounted to 10887 kg over the 24 years or 454 kg ha^?1 year^?1, about half of this difference (45%) resulting from soil erosion in plowed soils. The balance of gain in SOM with no till (249 kg ha^?1 year^?1) was due to SOM sequestration with no till. No‐till management reduced soil erosion, increased SOM, and enhanced soil physical characteristics.     

Determination of Soil Feature Effects on Plant-Available Phosphorus Extraction using Response Surface and Cate–Nelson Methodology

In this study, four soil extraction methods (Olsen, Soltanpour, Mehlich 3, and water saturation) were used to identify optimal concentrations of phosphorus (P) required for plant growth. Olsen soil extraction for P was the most appropriate method for soil types of this study as the greatest correlation coefficient for soil-test P and with plant factors was achieved. The optimal amount of soil features (pH, organic carbon, lime, gypsum, and clay) determined by using response surface methodology (a new optimization method) were 7.49, 0.66, 41.82, 4.21, and 31.34, respectively. More soil P was extracted when the soil had optimal amounts of these features, showing each feature had a significant effect on extracted soil P. Furthermore, the graphical method of Cate–Nelson determined the optimal amounts of P using Olsen, Soltanpour, Mehlich 3, and saturation extract methods for wheat as 15, 6.5, 35, and 1.5 mg kg^?1 soil in nongypsic soils and 17, 3.5, 45, and 2.5 mg kg^?1 soil in gypsic soils.     

Assessment of Soil Potassium Sufficiency as Related to Quantity‐Intensity in Montmorillonitic Soils

Abstract

No studies have been conducted to evaluate the potassium (K) quantity‐intensity (Q/I) relationships that exist in eastern South Dakota soils and how that may affect K fertility interpretations. The objectives of this study were to i) evaluate the K status of smectite‐dominant soils through quantity‐intensity relationships and (ii) relate the findings to current research on soil K release and plant availability. Soil and plant tissue samples were collected from eight different corn production fields across east‐central South Dakota. Samples were collected from areas where corn plants did or did not exhibit K deficiency symptoms. Quantity‐intensity plots were developed and used to derive the typical Q/I parameters. Little difference existed in Q/I parameters and the form of Q/I plots among field sites. The AR_e ^K and ΔK⁰ values ranged from 0.0013 to 0.0113, and ?0.47 to 0.18 cmol_c kg^?1, respectively, and most sites were considered K insufficient. The predominant phyllosilicate present in the clay‐sized fraction was montmorillonite with an estimated 17% tetrahedral charge. These soils would not be expected to contribute much plant‐available, nonexchangeable K and would be in need of frequent K fertilization. Presumably, these and similar soils, upon K exhaustion, rely heavily on K released from K‐bearing silt‐sized particles and may be highly dependent on surface‐controlled dissolution processes for labile K replenishment. Additional research needs to be conducted concerning the release kinetics of K from K‐bearing minerals of these soils.     

Cultivation‐Induced Effects on the Soil Organomineral Matrix and Their Bearing on Crust Development on Two Soil Formations from Tanzania

Abstract

Land degradation as a result of land‐use practices is a major environmental concern to sustainable agricultural production in Tanzania. The effect of clearing and long‐term cultivation on physical, chemical, and biological characteristics is described in two representative soil formations from eastern Tanzania: Mkindo (Eutric Fluvisol) in the Mvomero district and Mafiga (Ferric Lixisol) in the Morogoro district. The results have shown that in the Mkindo site, 10 years of continuous rice cultivation has led to severe changes in most characteristics of the soil. Significant effects of cultivation coincide with those considered to favor clay dispersion and crusting phenomena, including changes in soil reaction, clay content, and mineralogy as well as generalized desaturation of the exchange complex, increasing sodicity, and severe losses of soil organic matter (SOM). In contrast, at the Mafiga site, 30 years of a less disturbing cultivation system, including periodic fallows, have also modified some soil characteristics but to a lower extent than at Mkindo. Decreased soil colloidal properties at the Mkindo site and lower stability against biological degradation, reflected by carbon (C)–release curves, than the Mafiga site could be causally connected to clay illuviation processes leading to accumulation of calcium (Ca) and magnesium (Mg) but mainly caused by changes in SOM characteristics such as losses of humic (HA) and fulvic acid (FA) and accumulation of humin.     

Carbon Dioxide Emission from Black Soil as Influenced by Land‐Use Change and Long‐Term Fertilization

Land‐use change and soil management play a vital role in influencing losses of soil carbon (C) by respiration. The aim of this experiment was to examine the impact of natural vegetation restoration and long‐term fertilization on the seasonal pattern of soil respiration and cumulative carbon dioxide (CO₂) emission from a black soil of northeast China. Soil respiration rate fluctuated greatly during the growing season in grassland (GL), ranging from 278 to 1030 mg CO₂ m^?2 h^?1 with an average of 606 mg CO₂ m^?2 h^?1. By contrast, soil CO₂ emission did not change in bareland (BL) as much as in GL. For cropland (CL), including three treatments [CK (no fertilizer application), nitrogen, phosphorus and potassium application (NPK), and NPK together with organic manure (OM)], soil CO₂ emission gradually increased with the growth of maize after seedling with an increasing order of CK < NPM < OM, reaching a maximum on 17 August and declining thereafter. A highly significant exponential correlation was observed between soil temperature and soil CO₂ emission for GL during the late growing season (from 3 August to 28 September) with Q₁₀ = 2.46, which accounted for approximately 75% of emission variability. However, no correlation was found between the two parameters for BL and CL. Seasonal CO₂ emission from rhizosphere soil changed in line with the overall soil respiration, which averaged 184, 407, and 584 mg CO₂ m^?2 h^?1, with peaks at 614, 1260, and 1770 mg CO₂ m^?2 h^?1 for CK, NPK, and OM, respectively. SOM‐derived CO₂ emission of root free‐soil, including basal soil respiration and plant residue–derived microbial decomposition, averaged 132, 132, and 136 mg CO₂ m^?2 h^?1, respectively, showing no difference for the three CL treatments. Cumulative soil CO₂ emissions decreased in the order OM > GL > NPK > CK > BL. The cumulative rhizosphere‐derived CO₂ emissions during the growing season of maize in cropland accounted for about 67, 74, and 80% of the overall CO₂ emissions for CK, NPK, and OM, respectively. Cumulative CO₂ emissions were found to significantly correlate with SOC stocks (r = 0.92, n = 5, P < 0.05) as well as with SOC concentration (r = 0.97, n = 5, P < 0.01). We concluded that natural vegetation restoration and long‐term application of organic manure substantially increased C sequestration into soil rather than C losses for the black soil. These results are of great significance to properly manage black soil as a large C pool in northeast China.     

Methods to Estimate Aggregate Protected Soil Organic Carbon, 2: Does the Grinding of the Plant Residues Affect the Estimations of the Aggregate Protected Soil Organic Carbon?

A method to estimate the amount of soil organic carbon (SOC) physically protected within macroaggregates (>200 μm) consists of crushing soil samples and measuring the following SOC mineralization increase. This study investigated the effect of grinding the plant residues during soil crushing on the calculated amount of the protected SOC on two tropical soils (Arenosol and Ferralsol). Incubations of crushed and uncrushed soil samples amended with ground or unground plant residues were conducted. Our results showed that soil crushing increased SOC mineralization and that the presence of plant residues enhanced soil respiration also. The plant residues of the two soils had different decomposition rates, but grinding plant residues did not increase the amounts of cumulative carbon (C) mineralized after the 28 days of the experiment. We propose that the extra C mineralized after soil crushing is due to the breakdown of the soil structure and not to the grinding of plant residues.     

Soil‐grinder type effects on grams of soil scooped

Abstract

Soil preparation can affect soil test results. This study was conducted to compare soil‐grinder effects on grams of soil scooped. Soil samples (n=15,000) were ground by two types of soil grinders, a roller and hammer mill, and then the soil was sieved (10‐mesh), and scooped with a one‐gram scoop (0.85 cm³). The contents of the soil scoop were weighed. Grams of soil scooped ranged from 0.4 to 1.8 g for both soil grinders. The bell‐shaped distribution was centered around 0.8 and 1.0 g for the roller‐ and hammer mill‐type grinder, respectively. When the soil was ground by the roller‐type grinder, 85% of the ground soil was retained on a 50‐mesh sieve. In contrast, with the hammer mill grinder, 45% of the soil was retained on a 50‐mesh, 13% retained on a 100‐mesh, and 42% passed a 100‐mesh sieves. The “heavier” soil scoops with the hammer mill grinder could be explained by the fact that the finer soil particles could pack into the voids that the coarse soil particles created. Bray extractable P and ammonium actetate extractable K, Mg, and Ca were increased 11 to 15% by the “heavier” scooping weight. Grams of soil scooped and soil test levels were affected by the type of soil grinder and soil type.     

Effect of Grinding on Soil Extraction by Aqua Regia, 2 M Nitric Acid,and Mehlich 3

Abstract

The effect of grinding on soil extraction was determined for two soil fractions and three extractants. Arsenic (As), beryllium (Be), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), vanadium (V), and zinc (Zn) were extracted by aqua regia and 2 M nitric acid. Mehlich 3 extractant was used for determination of potassium (K), magnesium (Mg), calcium (Ca), phosphorus (P), iron (Fe), and aluminum (Al). One hundred forty‐seven agricultural soil samples representing all major soil types, climatic regions, and proportions of agronomic cultures in the Czech Republic were collected for the study. Particle size fractions smaller than 2 mm and smaller than 0.150 mm were chosen for investigation. Extraction of elements by aqua regia was similar for both size fractions of soil. Cold 2 M nitric acid is a weaker extractant than aqua regia, and a statistically significant increase in extractable Be (5%), Cd (6%), Co (11%), Cu (5%), Ni (5%), and V (2%) was measured with the finely ground soils. An increase for the finer fraction for K (10%) and Mn (25%) was found for Mehlich 3. A more complex nonlinear relationship was found for Mehlich 3 extractable Al and Fe. This was probably caused by a more intensive re‐adsorption of Fe and Al to the finely ground soils.     

Influence of Loss‐on‐Ignition Temperature and Heating Time on Ash Content of Compost and Manure

Abstract

Loss‐on‐ignition (LOI) is a simple method for determining ash content, and by reciprocation, organic matter content of compost and manure. However, reported ignition temperatures and heating times for LOI measurements vary widely, and this brings into question the accuracy of one specific combination of ignition temperature and heating time over another. This study examined the effect of 42 temperature‐heating time combinations (six ignition temperatures from 400 to 650°C in 50°C increments by seven heating times of 1, 2, 8, 12, 16, 20, and 24‐h) on the ash content of a finished compost and a fresh manure. The experiment included the 550°C for 2‐h method recommended in Test Methods for Evaluation of Compost and Composting. The magnitude of the decrease in ash content due to increase in temperature was not consistent across all heating times. For example, after a 1‐h heating time for compost, ash content was 75.7% at 400°C and 67.5% at 650°C, compared to 69.6% at 400°C and 66.8% at 650°C after 24‐h. Irrespective of heating time, an ignition temperature of 400°C overestimated ash content for both compost and manure compared to the TMECC method. The TMECC method with its moderate temperature and short heating time requirement could reduce energy costs without affecting ash content results.     

Determination of Soil Base-Suluble Se by Anodic Stripping Voltammetrywith Aurum Thin-Film Electrode

Determination of soil Se by anodic stripping voltammetry(ASV) with aurum thin-film electrode(ATFE)overcomes the interference of gold peak with selenium peak,and thus has a higher sensitivity with the miniumum detectable concentration being 0.017μg/mL,the standard deviation of the measured results leww than 0.012μg/g,the coefficient of variation lwoer than 10% ,and the recovery rate between 86% to 103%.Besides the measurement conditions,the digestion of soil sample was also studied in detail.     

Bicarbonate Had Greater Effects Than High pH on Inhibiting Root Growth of Zinc‐Inefficient Rice Genotype

Abstract

Effects of bicarbonate (10 mM as NaHCO₃) and high pH (pH 8 buffered with HEPES) separately on root growth and accumulation of organic acids in the roots of zinc (Zn)‐efficient (IR36) and Zn‐inefficient (IR26) rice genotypes (Oriza sativa L.) were investigated in this study. The results indicated that shoot dry matter yields were decreased more by bicarbonate than by high pH for the Zn‐inefficient genotype, but not affected for the Zn‐efficient genotype. Root dry weights, especially root length, was significantly decreased by bicarbonate and high pH treatments for the Zn‐inefficient genotype, whereas was considerably enhanced by only bicarbonate treatment for the Zn‐efficient rice genotype. The reduction in root growth of the Zn‐inefficient rice genotype and the enhancement of root length in the Zn‐efficient genotype were greater when plants grown with bicarbonate than with high pH treatment. Accumulation of malate, citrate, and fumarate in roots of the two genotypes increased considerably due to both high pH and bicarbonate treatments, but to a greater extent for the Zn‐inefficient than for the Zn‐efficient cultivars. After an 8‐day treatment, more organic acids accumulated in the roots of the Zn‐inefficient genotype (IR26) when plants grown with bicarbonate than at high pH, but this was not the case for the Zn‐efficient genotype. The influence of root growth by bicarbonate appeared to be one of the major factors for the sensitivity of rice genotypes to Zn deficiency in calcareous soils. The greater inhibitory effect of bicarbonate than high pH on root growth of the Zn‐inefficient genotype might result from an excessive accumulation and inefficient compartmentation of organic acids, particularly citrate and malate, in the root cells.     

Effects of supplemental‐nitrogen on the quality of rice proteins

A study was conducted on the effect of supplemental nitrogen (N) (20 hg/ha) applied as a foliar spray or to the soil on seed production, protein percentage, and protein fractions of rice. Plants were grown in a greenhouse over two different periods of time, i.e., August 1988 to January 1989 (Period I), and December 1988 to April 1989 (Period II). Nitrogen was applied to the leaves 10 and 20 days after anthesis (DAA), and to the soil at anthesis and at 15 DAA. Average temperature was 28.7°C during Period I and 32°C during Period II, corresponding to 18.7 and 22.0 growing degree‐day/day (GDD/day), respectively. The difference in GDD/day reduced the plant cycle from 130 days during Period I to 109 days during Period II. Plants grown during Period II had larger numbers of spikelets, a higher percentage of “full grown grains”;, and higher grain weight. Although percentage crude protein was about the same for the two periods, prolamin content was increased and the albumin+globulin fraction was decreased during Period II, but with no difference in glutelin content. The increase in number of spikelets, percent full grains, and grain weight appeared to result in a greater energy demand for plants grown during Period II. This may explain the increase in prolamins, since prolamin synthesis requires less energy than globulin or albumin synthesis. There was a simultaneous decrease in albumin and globulin synthesis during Period II. The content of glutelins, which represent the major reserve proteins in rice grains, was constant during both periods.     

Effect of the Extraction Period on the Routine Assessment of Soil P Status by Ion‐Exchange Resin Membranes

The cation–anion exchange resin membrane (CAERM) system is one of the most promising alternative methodologies for the assessment of soil phosphorus (P) availability. Nevertheless, the CAERM method has a recommended period of extraction (16 h) that limits its applicability. With the aim to improve the use of CAERM in routine laboratory work, seven extraction times were studied and compared for repeatability and biological accuracy, using 150 samples of soils and covering a wide range of properties. The results showed dissimilar quantities of extractable P, according to the nature of soils and the period of extraction time. On average of all soils, values of extractable P ranged from a 2.4 mg kg^?1 and 26.7 mg kg^?1 in 0.25‐h and 16‐h extraction times, respectively. Relative to the repeatability aspects, the results reveal a tendency of increasing results with the decrease of the period of extraction, showing coefficient variation (CV) values ranging from 5% (16 h) to 14% (0.25 h). All the extraction periods tested for the CAERM presented highly significant values of r (0.824–0.943) between extractable P and each of the three biological parameters: relative yield of ryegrass, P content, and P uptake. Considering the three biological parameters simultaneously, the best results were obtained for extraction periods of 8 h, 2 h, and 4 h. Based on the results, and considering both practical and accuracy aspects, it is conclude that 2 h of extraction is a valid alternative to the 16‐h standard extraction period for the CAERM methodology.     

Implementation of Soil Lime Requirement by a Single‐Addition Titration Method

Abstract

Buffers for determining a soil's lime requirement (LR) sometimes contain hazardous chemicals. Our objective was to implement a single‐addition titration with calcium hydroxide [Ca(OH)₂] to determine the LR of soils. The soil pH buffering capacity is calculated from the rise in pH from a single addition of base. The LR is calculated from the soil pH buffering capacity, the target pH, and initial soil pH. The LR of 531 randomly selected client samples determined by single‐addition titration were slightly higher than by the Adams–Evans (AE) buffer procedure when LRs were less than 1800 lb per acre. The new procedure recommended about 11% less lime than AE at LRs greater than 1800 lb per acre. Independent evaluations of samples that gave the most widely different LR revealed that the single‐addition titration was more accurate and more precise than the AE buffer.