Influence of air drying and soil gas‐phase carbon dioxide on DTPA‐extractable iron in calcareous soils

Abstract

The extraction of a field‐moist soil with DTPA will result in a level of extractable iron (Fe) lower than that of the air‐dried soil. Soil gas‐phase carbon dioxide (CO₂) levels may be considerably higher than ambient atmospheric levels, especially in wet soils in the field. This study was undertaken to determine whether gas‐phase CO₂ level influences the quantity of Fe extracted by DTPA. Three moist calcareous soils were incubated for 21 days, each at three different partial pressures of CO₂, after which the moist soils were extracted with DTPA. A sample of each soil was also air dried, and was subsequently extracted with DTPA. In each case, DTPA‐extractable Fe from the moist sample was lower than that from the air‐dried sample; however, DTPA‐extractable Fe increased with increasing CO₂ partial pressure of in the moist soils. DTPA‐extractable Fe concentration for a given soil following air drying was not significantly influenced by the CO₂ partial pressure during incubation of the originally field‐moist soil. DTPA‐extract pH of the moist soils followed the same trend as soil‐solution pH (i.e., as CO₂ concentration of the soil gas‐phase increased, soil solution pH and DTPA extract pH both decreased); however, the slope of the pH versus log P_CO2 curve was less pronounced in the DTPA extract due to the buffering capacity of the triethanolamine. From this study, it is concluded that elevated soil gas‐phase CO₂ partial pressure does not contribute to the lower level of DTPA‐extractable Fe observed when the extraction is performed on a field‐moist versus an air‐dried soil; increased CO₂ partial pressure actually resulted in a slight increase in concentration of DTPA‐extractable Fe obtained from a field‐moist soil.     

The determination of phosphate‐extractable sulphate in soil with an anion‐exchange membrane

Abstract

A method for extracting sulphate from soils using strips of a phosphated anion‐exchange membrane is described. The results obtained by this method are in good agreement with those obtained by extraction with Ca(H₂PO₄)₂solutions and the method has a number of practical advantages over the use of phosphate solutions. No charcoal treatment, centrifuging or filtering is required and the strips are reuseable. No organic interferences are encountered during the turbidimetric measurement of the extracted sulphate.     

Performance characteristics in the determination of soil‐water pH and soil‐SMP buffer pH using a flow‐through junction combination electrode

Abstract

A laboratory robot has been used to assess the performance of a commercially available flow‐through junction pH electrode. The electrode was tested for accuracy and precision in the determination of soil‐water pH (pH_w) and the Shoemaker, McLean, and Pratt buffer solution pH (pH_SMP). The significance of the pH_SMP determination lies in subsequent calculations of soil lime requirement (LR). Response times and hysteresis effects were compared under different operating conditions.     

Use of a solid‐state chloride electrode for chloride determinations in soil extracts

Abstract

Studies were conducted to evaluate the use of a solid‐state chloride electrode for chloride determinations in soil extracts. The solid‐state chloride ‐electrode was used as an end point detector in the titration of chloride with AgN0₃ and direct reading of chloride in solution. The solid‐state electrode gave results very similar to those obtained with a silver electrode (r = 0.999) when used as an end point detector. Values obtained using the solid‐state electrode as a direct reading electrode were also well correlated (r = 0.998) but were slightly higher than results obtained by titration with a silver electrode.     

Influence of soil particle size and grinding on bray‐2 extractable phosphorus

Abstract

The influence of soil particle size and soil fine grinding on Bray‐2 extractable phosphorus (Bray‐2P) was studied. Air‐dried and 2‐mm mesh‐sieved soil was separated into six particle size classes: <0.075, 0.075–0.106, 0.106–0.25, 0.25–0.425, 0.425–0.85, and 0.85–2 mm. The lowest amounts of Bray‐2P were found in the 0.425–0.85 and 0.85–2 mm fractions and the highest in <0.075 mm fraction. When ground for 3 min, the amount of Bray‐2P increased in the fractions larger than 0.25 mm, whereas it decreased in the fractions smaller than 0.25 mm. In the large fraction (0.425–0.85 mm), grinding for 1 to 3 min led to an increase in the amount of Bray‐2P, but grinding for 9 to 18 min caused a decrease. In contrast, in the small fraction (<0.075 mm), the amount of Bray‐2P decreased by grinding for 1 min. The large and small fractions that were ground absorbed P in proportion to the grinding time during the extraction‐filtration period.     

Lime requirement determination of tropical peat soil using buffer‐pH methods

Abstract

A study was conducted to calibrate and evaluate five buffers for the lime requirement (LR) determination of tropical peat soil. The buffers tested were the Shoemaker‐McLean‐Pratt (SMP); Mehlich; 0.1M ammonium acetate (NH₄OAc); 0.1M barium acetate [(Ba(OAc)₂]; and 0.1M calcium acetate [Ca(OAc)₂]. Calibration was done by comparing the precision of linear regression equations adjusted to the relationships between the LR rates required to achieve pH 5.0 measured in a 1: 4 (soiltwater) ratio as determined by incubation and soil‐buffer pH values. Incubation LR using calcium carbonate (CaCO₃) to achieve pH 5.0 by peat soil was utilized to calibrate each buffer. Evaluation was carried out by assessing the LR from the calibrated buffers which estimate the LR nearest to the target pH of 5.0. The calibration study showed that the SMP and Mehlich buffers were less precise than the Ba(OAc)₂, NH₄OAc, and Ca(OAc)₂ buffers. The evaluation study indicated that the Ba(OAc)₂ buffer is the most accurate, followed by NH₄OAc and Ca(OAc)₂ buffers. The Ba(OAc)₂ buffer method is recommended for LR determination of tropical peat soil and NEUOAc or Ca(OAc)₂ as an alternative method.     

Effects of calcium lignosulphonate on Mehlich‐III extractable calcium,magnesium, and potassium quantity‐intensity relationship in the soil with or without potassium dihydrogen phosphate

Abstract

Calcium lignosulphonate (CaLS), a waste product from the pulp and paper industry, is expected to affect reaction of K fertilizer in the soil, thus influences their availability to crops. A clay soil (Typic Humaquept) was incubated with various amounts of CaLS (0 to 150 g kg^‐1 soil) and potassium dihydrogen phosphate (0–25.64 mmol kg^‐1 soil) for 240 h under moist conditions at 5 and 15°C. Subsamples were extracted with deionized water and the Mehlich‐III (M3) solution for the analyses of pH, and P, Ca, K and Mg concentrations and K adsorption (K_ad). Higher temperature reduced M3 extractable K (K_M3). CaLS and K additions increased M3 extractable Mg (Mg_M3) with Ca contributed more than did K as indicated by the standardized estimates. Additions of CaLS increased K_M3. Potassium adsorption decreased with the increases in CaLS addition rates. Significant positive linear relationships were observed between K_ad and the concentration ratio of [K⁺]/[Ca²⁺]^½, suggesting that the potassium buffering capacity of the soil was reduced by the additions of CaLS, with the desugared CaLS being more effective than the non‐desugared CaLS. The increased slope values with the increases in CaLS additions of the linear relationships between K_M3 and [K]/[Ca²⁺]^½ indicated that CaLS improved the quantity and intensity relationships and increased the power of the soil supplying plants with K.     

Distribution of DTPA‐extractable Fe,Zn, and cu in soil particle‐size fractions

Abstract

To examine the distribution of DTPA‐extractable Fe, Zn, and Cu in clay, silt, and sand fractions; surface soils were collected from cultivated fields of North Dakota, South Dakota, West Virginia, Iowa, Ohio, and Illinois. Clay, silt, and sand fractions were separated after sonic dispersion of soil water suspension and analyzed for DTPA‐extractable Fe, Zn, and Cu. In general, clay had the highest and sand the lowest amount of DTPA‐extractable metals. Consequently, clay had the highest and sand the lowest intensity and capacity factors for these metals since DTPA micronutrient test measures both these factors.     

Seasonal levels of water‐extractable cations and anions in soil under blight‐affected and healthy citrus trees

Abstract

Soil samples were collected under blight‐affected and healthy citrus trees at 30‐day intervals for 24 months, at 20‐to 50‐cm depth. Analyses of water extracts (1:1 soil: water) for K, Ca, Mg, Na, SO₄, and Cl showed few differences in cations, but lower anion levels under blighted trees. The cation/anion ratio was significantly higher under blight‐affected trees. Samples collected once at different locations in the same time period showed the same differences. In one location, K was lower and Na higher under healthy trees than under blight‐affected trees, in others K was higher too.     

Simultaneous determination of soil aluminum,ammonium‐ and nitrate‐nitrogen using 1 M potassium chloride extraction

Abstract

Determination of soil aluminum (Al), ammonium‐nitrogen (NH₄‐N), and nitrate‐nitrogen (NO₃‐N) is often needed from the same soil samples for lime and fertilizer recommendations, but Al has to be extracted and quantified separately from NH₄‐N and NO₃‐N according to present methods. The objective of this study was to develop a reliable method for simultaneous analyses of soil Al, NH₄‐N and NO₃‐N using a Flow Injection Autoanalyzer. Thirty‐five soil samples from different locations with wide ranges of extractable Al, NH₄‐N and NO₃‐N were selected for this study. Aluminum, NH₄‐N and NO₃‐N were extracted by both 1 M and 2 M potassium chloride (KCl), and quantified using a LACHAT Flow Injection Autoanalyzer simultaneously and separately. One molar KCl was found to be a suitable extractant for all three compounds when compared to 2 M KCl. The 1 M KCl extract proposed could aid in decreasing the costs associated with simultaneous NH₄‐N, NO₃‐N, and Al analyses. Results of those three compounds analyzed simultaneously were not statistically different from those analyzed separately in 1 M KCl solution. This new procedure of simultaneous determination of NH₄‐N, NO₃‐N, and Al increases efficiency and reduces cost for soil test laboratories and laboratory users.     

Screening for phyto‐toxic contaminants in an industrial source of nutrients intended for foliar and root fertilization

Plant screening assays were used to determine whether significant levels of growth inhibitory and phytotoxic contaminants were present in a new industrial source of potassium dihydrogen phosphate fertilizer intended for foliar and root application. Maize (Zea mays L.) plants hydroponically cultured in a controlled environment chamber, were used for the assays. The threshold concentration of industrial potassium phosphate which just caused burn damage symptoms, when applied as standard droplets to the leaf surface with Tween 80 wetting agent was 0.5M. The comparative threshold concentration for damage by an ultrapure analytical grade of potassium phosphate was >0.6M. Thus, the industrial grade had slightly higher toxicity for leaf application. Effects on plants of supplying industrial and analytical grade phosphates via the roots were also compared. Root and leaf elongation kinetics, mature leaf cell lengths, apparent capacity for leaf cell production, shoot ontogeny, and shoot fresh weight yields were determined at low and high potassium phosphate concentrations. The effects of analytical and industrial grade fertilizer salts were equivalent. We suggest that these rapid and relatively simple plant screening assays can provide a useful safety check, prior to large scale field trails, for fertilizer nutrients produced by new industrial processes.     

Variation in extraction of calcium from dry‐ashed embryos of cucurbits and other lipid‐rich seeds

Abstract

All cucurbit embryos analyzed showed a decrease in the ease with which calcium could be extracted from the ash as the ashing temperature increased beyond 600°C. After ashing at 500°C, the Ca in the cucurbit ash was fully extracted by 5% o HC1. After 650°C ashing, lower than expected Ca levels were obtained unless additional ash treatment with HNO₃ and HC1 was applied. Castor bean embryos plus endosperm showed the same effect but other oily embryos tested did not need ash treatment to fully extract Ca from either the 500 or 650°C ash. Neutron activation analysis indicated that the differences in ash characteristics were related to the differences in concentrations of K and P in the embryo tissues.     

Acid soil tolerances of two wheat cultivars related to soil Ph,KCl‐extractable aluminum and degree of aluminum saturation

Aluminum toxicity, associated with soil acidity, is a major growth‐limiting factor for plants in many parts of the world. More precise criteria are needed for the identification of potential Al toxicity in acid soils. The objective of the current study was to relate the acid soil tolerances of two wheat cultivars to three characteristics of an acid Tatum subsoil (clayey, mixed, thermic, typic Hapludult): pH in a 1:1 soil to water suspension; KCl‐extractable Al; and degree of Al saturation. Aluminum‐tolerant ‘BH 1146’ (Brazil) and Al‐sensitive ‘Sonora 63’ (Mexico) wheat cultivars were grown in greenhouse pots of soil treated with CaCO₃ to establish final soil pH levels of 4.1, 4.6, 4.7, 4.9, 5.2 and 7.3. Soil Al, Ca and Mg were extracted with 1 N KCl, and Al saturation was calculated as KCl‐Al/KCl Al + Ca + Mg%.

Within the soil pH range of 4.1 to 4.9, BH 1146 tops and roots produced significantly more dry matter than did those of Sonora 63; however, at pH 5.2 and 7.3, the top and root yields of the two cultivars were not significantly different. Significant cultivar differences in yield occurred over a range of 36 to 82% saturation of the Tatum soil. Graphs of relative top or root yields against soil pH, KCl‐extractable Al and Al saturation indicated that the two cultivars could be separated for tolerance to Tatum soil under the following conditions: pH less than 5.2 (1:1 soil‐water); KCl‐Al levels greater than 2 c mole kg^‐1 and Al saturations greater than 20%. Results demonstrated that any soil test used to predict Al toxicity in acid soils must take into account the Al tolerances of the plant cultivars involved.     

Effects of phosphate,nitrate and chloride on calcium,magnesium and manganese content of cigar‐wrapper tobacco

Abstract

Nutrient solutions containing three levels of phosphate, nitrate, and chloride were applied to cigar‐wrapper tobacco (Nicotiana tabacum L.) plants growing in sand culture for a period of 18 days. Concentrations of other nutrient elements in the nutrient solutions were held constant and the solutions were applied to pots as needed to maintain favorable moisture conditions for plant growth. Plants were in the two leaf stage when transplanted and were maintained on a single nutrient solution for 38 days before treatments were started. At the end of an eight weeks growing period, plant leaves were harvested and analyzed for Ca, Mg, and Mn. Dry matter yield was significantly (P=0.01) increased when 2 mM/1 of Ca(NO₃)₂ replaced an equivalent amount of Ca(H₂PO₄)₂ or CaCl₂ in the nutrient solution. Nitrate significantly (P=0.05) increased Ca and Mg content and decreased Mn concentration in leaf tissue in comparison to chloride. Calcium and Mg content were significantly (P=0.05) decreased and Mn content of tobacco leaves was increased by phosphate in comparison to nitrate and chloride.     

The determination of ammonium and chloride by an auto‐analyser for the measurement of cation exchange capacity of soils

Abstract

An auto‐analyser method has been developed for the simultaneous determination of NH₄ ⁺ and Cl^‐ in Ca(NO₃)₂/KNO₃ extracts of NH₄Cl treated soils for cation exchange capacity measurements. The method gives satisfactory agreement with manual titration procedures.     

Energy dispersive X‐ray fluorescence for rapid potassium,calcium, and chloride diagnosis in barley

Barley (Hordeum vulgare L. cv Doriru) leaf samples were collected from a field comprising three plots, plot F chemical fertilizer treated, plot S receiving sewage sludge and sawdust mixed compost, and plot H receiving sewage sludge and rice husk mixed compost. Relative concentrations of selected elements, potassium (K), calcium (Ca), and chloride (Cl) of young, mature, and old barley leaves were determined by microscopic energy dispersing X‐ray fluorescence (EDXRF). The objective of this investigation was to verify the applicability of EDXRF for rapid nutrient element diagnosis of plants. Typically whole leaves were washed in deionized‐distilled water and dried by ironing for analysis. Intact dried barley leaf sample irradiation was accomplished with X‐rays obtained from an X‐ray tube focused on an area <100 μm of the respective sample specimen surface. The EDXRF provided sufficient sensitivity for relative concentrations of K, Ca, and Cl. Element content data of all the elements investigated, specifically K, resulted in adequate plant nutrient element values to diagnose K insufficiency in barley leaves taken from plants in the sewage sludge receiving plots. Potassium was more densely accumulated in the new leaf than in mature and old leaves in case of plants from the S and H plots. In contrast, such K accumulation was more dense in old and mature leaves than young leaves in case of plants from the F plot. However, Cl and Ca coupling in barley leaves from all of the F, S, and H plots had shown the similar pattern of distribution and followed the order: old > mature > young. Therefore, EDXRF can be an easy, rapid, and practical method for diagnosing the elemental content of plant tissues and thereby help to aid plant growth and development through timely supplements of the required element(s).     

Effect of extractable zinc,phosphorus, and soil ph on zinc concentrations in leaves of field‐grown corn

Abstract

The variability in corn yield responses to applications of Zn fertilizer appears to be associated with several complex soil and climatic factors that affect the availability of endogenous soil Zn to the crop under specific conditions. Among the soil chemical properties that influence availability of endogenous Zn are soil pH, organic matter content, and extractable P. Over a period of several years, soil and plant analysis data were collected from 54 field experiments, field trials, and diagnostic visits to producer's fields. These data were subjected to multiple regression analysis, resulting in an equation: Zn_leaf = 37.14 + 1.513 Zn_st ‐4.04 pH_st ‐ 1.791 ln(P_st/100) where Zn_st, pH_st, and P_st were 0.1N HC1 extractable soil Zn (kg/ha), 1:1 soil‐water pH, and Bray's 1 extractable soil P (kg/ha), respectively. These factors accounted for 67% of variation in leaf Zn, which was a large portion of the variability in Zn_leaf considering that climatic conditions, management levels, and varietal differences were uncontrolled in most instances. Using the previously published critical level in the leaf opposite and below the ear as 17 μg Zn/g, these data can be used to set required soil test levels of Zn at different levels of extractable P and soil pH. Inadequate levels of extractable Zn would range from 2.5 (at pH 6.0, P = 70 kg/ha) to, 9.5 kg/ha (at pH 7.5, P = 420 kg/ha).     

A quick‐test procedure for soil and plant tissue nitrates using test strips and a hand‐held reflectometer

Abstract

Development of a nitrate quick‐test for use by fanners or field consultants would likely encourage the use of plant tissue and soil nitrate tests as a means to improve nitrogen management. To evaluate a quick‐test method, nitrate concentrations in plant tissue and soils were measured using commercially available nitrate test strips and a hand‐held reflectometer. The results were compared with those obtained with standard laboratory methods. Test strip accuracy and precision and reflectometer precision were determined over a 10 day period using standard KNO₃solutions and colored paper strips. Coefficients of variation ranged from 22.4 to 9.5 percent for the test strips and from 3.5 to 1.6 percent for the reflectometer. Quick‐test results were highly correlated with laboratory results for both plant tissue nitrate (r=0.87) and soil nitrate (r=0.98) concentrations. Results indicated that test strips provide a rapid, reasonably accurate and precise method to determine nitrate concentrations in both soil and plant material     

Nitrate versus chloride nutrition effects in a soil‐plant system on the growth,nitrate accumulation,and nitrogen,potassium, sodium,calcium, and chloride content of carrot

The experiment was conducted to evaluate the effects of various nitrate/ chloride (NO₃/Cl) ratios on growth, nitrate accumulation, and mineral absorption in carrot, Daucus carota L., plants in a controlled environment. The experiment included two Cl sources [potassium chloride (KC1) and calcium chloride (CaCl₂)] and five NO/Clratios at 100/0, 90/10, 80/20, 70/30, and 60/40 with total‐nitrogen (N) concentration of 400 mg NO₃ kg^‐1 soil in 100/0 treatment. Fresh and dry weights of shoots and storage roots, and length and diameter of storage roots increased significantly with mixed NO₃/C1 treatments with both Cl sources as compared to single NO₃ (100/0) treatment. Growth was enhanced up to the 80/20 NO₃/C1 treatments. With Cl present in the treatments, the concentration of total‐N unchanged and NO₃ decreased in plants, and Cl and potassium (K) increased with the Cl sources. In KC1 treatments, Na absorption decreased. Calcium (Ca) content of the plants significantly differed by the treatments. It was concluded that N fertilization provided with combined Cl forms and NO₃/Cl rates can enhance production of better quality carrot and at the same time decrease of the N fertilizer input.