Optimization of sample ph and temperature for phosphorus‐31 nuclear magnetic resonance spectroscopy of poultry manure extracts

Abstract

Organic phosphorus (P) compounds can be characterized using nuclear magnetic resonance (NMR) spectroscopy provided conditions are suitable for detecting the NMR signal. The objective of the research was to optimize pH and temperature conditions for turkey manure extracts prior to analysis of organic P compounds using NMR. Samples of turkey manure were extracted with 0.25 MNaOH + 0.05 MEDTA. The extracts were lyophilized and resolubilized in distilled H₂O before analysis on a General Electric GN500 NMR spectrometer. Initial ³¹P NMR experiments were run to determine the optimal instrumental parameters for ³¹P studies. Samples were titrated to seventeen pH values ranging from 4.0 to 13.2. Samples adjusted to pH 10.0 had the greatest spectral resolution. A seven‐by‐three factorial experiment was used to investigate the effect of seven temperatures (5,10,20,30,40,50, and 60°C) on three separate samples at pH 6.5,9.0, or 10.0. Spectra resolution was greatest at pH 10.0 and 20°C.     

Pear seedling response to phosphorus in a phosphorus‐fixing soil

Abstract

The effect of P on growth of ‘Bartlett’ pear (Pyrus communis L.) seedlings was evaluated on the P‐fixing, Parkdale soil (Vitrandepts) from Oregon, USA. The P treatment levels were 0.03, 0.04, 0.06, 0.09, 0.15, 0.25, and 0.40 mg P/L of soil solution, based on a P‐sorption isotherm. At age 145 days, the dry weight response to P was significant. Seedlings required 0.25 mg P/L for maximum growth. This corresponds to 723 mg P/kg soil based upon the P‐sorption isotherm. Standard P soil tests did not accurately predict seedling response to P. About one‐half of the soil P was in the chemisorbed fraction.     

Colorimetric determination of phosphorus in citrate‐bicarbonate‐dithionite extracts of soils

Abstract

Existing colorimetric methods for determining phosphorus (P) in citrate‐bicarbonate‐dithionite (CBD) extracts from soils and sediments require pretreatments of extracts prior to the determination of the element. A method is proposed for the determination of P in CBD extracts without any chemical treatments. Maintaining the citrate concentration below 2.4 mM, maximum and stable absorbance develops in P‐Mo‐Sb system within one hour and remains stable for 20 hours. An evaluation of potential interference was made by adding varying amounts of P to CBD extracts over a range of extractable iron (Fe) and aluminum (Al) levels. Near 100 percent recovery of the added P suggests the applicability of the method to soils and sediments. Major advantages of the method are speed, simplicity, reliability and stability of the colored complex.     

Use of diffusion for automated nttrogen‐15 analysis of soil extracts

Abstract

Studies to evaluate the use of diffusion for automated ¹⁵N analysis of inorganic N in soil extracts showed that serious error can arise from use of the Devarda's alloy recommended for steam distillations and that the error can be avoided by using a commercial product of higher purity. These studies showed that serious error can also arise when NO₃ ^‐‐N is diffused following NH₄ ⁺‐N and that separate diffusions should be performed for NH₄ ⁺‐N and (NH₄ ⁺ + NO₃‐)‐N. Other work demonstrated that the plastic specimen containers employed for diffusion can be reused if acid‐washed, that diffusions can be performed using either light or heavy MgO without ignition to decompose carbonate, and that labeled NO₂‐is completely removed from soil extracts by treatment with sulfamic acid before diffusion. A comparison of ¹⁵N analyses by steam distillation and diffusion using extracts from two soils revealed better agreement for the soil having a lower content of organic matter. Substantial differences in analyses by the two techniques for the soil having a higher organic‐matter content were attributed to enzymatic conversions of inorganic N during the 6‐d diffusion period.     

Comparison of phosphate‐phosphorus and total phosphorus in DTPA extracts for assessing plant‐available phosphorus in soilless potting media

Abstract

Hakea francisiana and H. laurina were grown in soilless media based on pine bark, to which had been added one of the following phosphorus (P) sources: crushed bone, rock phosphate, calcined rock phosphate, sewage sludge, or sludge compost. Available P was assessed through extraction with unbuffered 2 mM DTPA. Similar regression equations between shoot P content and P in 2 mM DTPA extracts of the media at potting were obtained for both total P in the extract (determined by inductively coupled plasma emission spectrometry) and PO₄‐P. The difference between them was small compared with the variation caused by different rates of dissolution of P the various sources during the growing period. Extractants give only an approximate guide to plant P uptake when the medium contains sources that slowly dissolve during the growing period. Nevertheless, the data indicate that, irrespective of P source, the maximum P concentration in a 2 mM DTPA extract (1:1.5 v/v) of the medium that is tolerated by P‐sensitive plants is 3–4 mg/L. This is similar to the concentration found previously for superphosphate as the source of P.     

Effect of soil amendments on fractionation of Selenium‐enriched soil

Abstract

This study was to determine the effect of soil amendments on the fractionation of selenium (Se) using incubation experiments under simulated upland and flooded conditions. The treatments were as follows: 1) control [soil + sodium selenite (Na₂SeO₃) (1 mg Se kg^‐1)]; 2) control + calcium carbonate (CaCO₃) (5 g kg^‐1); 3) control + alfalfa (40 g kg^‐1); and 4) control + CaCO₃ (5 g kg^‐1) + alfalfa (40 g kg^‐1). After a 90‐day incubation, soil was sampled and fractionated into five fractions: 1) potassium sulfate (K₂SO₄)‐soluble fraction (available to plants); 2) potassium dihydrogen phosphate (KH₂PO₄)‐exchangeable fraction (potentially available); 3) ammonium hydroxide (NH₃H₂O)‐soluble fraction (potentially available); 4) hydrochloric acid (HCl)‐extractable fraction (unavailable); and 5) residual fraction (unavailable). Compared with the control, CaCO₃ increased the K₂SO₄ fraction at the expense of the NH₃H₂O fraction. Alfalfa increased both the K₂SO₄ and residual fractions but reduced the KH₂PO₄ and NH₃H₂O fractions. The CaCO₃‐alfalfa treatment had a similar effect to the alfalfa treatment alone. The comparison between the upland and flooded conditions showed that the flooded condition generally increased the residual fraction and decreased the potentially‐available fractions. In general, CaCO₃ was a better amendment because it not only increased the available fraction but also maintained the potentially available fractions at a high level. The application of Na₂SeO₃ and use of appropriate soil amendments can improve Se availability in soil.     

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.     

Critical soil phosphorus of a low‐P loess‐derived soil as affected by storage temperature

Abstract

Overwintering soil temperature may influence crop response to phosphorus (P) and indices of P availability in the humid, temperate, transitional climate of Tennessee. The effects of P fertilization and soil incubation temperature on sorghumsudangrass (Sorghum bicolor x S. Sudanese) grown on a Typic Hapludalf was investigated in a greenhouse study. In order to determine the effect of temperature on P availability, soils were incubated prior to cropping, at a constant temperature of 6°C or an average diurnal temperature of 24 and 36°C. Reagent grade Ca(H₂PO₄)₂.H₂O was used as the fertilizer source and applied at rates of 0, 10, 20, and 30 mg P kg^‐1 for the first test and 0, 20, 40, 60, and 80 mg P kg_‐ ¹ for the second test. Critical P concentration in the shoots for optimum yield was found to be 1.3 mg g‐¹, corresponding to soil solution and labile P concentrations of 5.5 μmol L^‐1 and 167 μg g^‐1, respectively. Optimum yield occurred for applications of >65 mg P kg^‐1 and was unaffected by soil incubation temperature. Applied P rates affected extractable P by five chemical extractants (Bray I, Bray II, Mehlich I, Mehlich III, and Mississippi), but soil incubation temperature had no affect. The extractants, however, were poorly correlated to plant P uptake and no one extractant appeared preferable to the others as an indicator of P availability.     

Evaluation of methods for nitrogen‐15 analysis of inorganic nitrogen in soil extracts: I. Steam‐distillation methods

Abstract

A study was conducted to evaluate conventional steam‐distillation techniques for N‐isotope analysis of inorganic forms of N in soil extracts. Extracts obtained with 2 M KCl from 10 diverse soils were treated with: (i) (¹⁵NH₄)₂SO₄ and KNO₃, (ii) (NH₄)₂SO₄ and K¹⁵NO₃, or (iii) KNO₃and Na¹⁵NO₂. Steam distillations were performed sequentially to determine NH₄ ⁺‐N and NO₃ ^‐‐N, and were also carried out to determine (NO₃ ^‐ + NO₂ ^‐)‐N or (NH₄ ⁺ + NO₃ ^‐ + NO₂ ^‐)‐N; a pretreatment with sulfamic acid was used to determine NO₃ ^‐‐N in the presence of NO₂ ^‐‐N. Recovery of added N ranged from 95 to 102%. Significant isotopic contamination was observed in sequential distillation of unlabeled NO₃ ^‐‐N following labeled NH₄ ⁺‐N; otherwise, analyses for ¹⁵N were usually within 1% of the values calculated by isotope‐dilution equations.     

Simplified procedure for rapid,manual analysis of nitrate in soil extracts by copper‐cadmium reduction

Abstract

An inexpensive modification of the commonly used manual nitrate (NO₃)‐nitrogen (N) analysis for soil extracts is described. This procedure uses multiple reductors of copperized cadmium (Cd) wire threaded through Teflon tubing and a peristaltic pump to rapidly pass a low volume of soil extract through the reductors at a constant flow rate. In excess of 150 prepared samples can be processed daily with minimum waste generation. Efficiency of reduction is >98% and precision of analysis (coefficient of variation) for replicate standards of known NO₃‐N concentration is excellent, at <0.5% over the concentration range 0.025 to 0.2 μg NO₃‐N mL^‐1. Column life and storage characteristics are high, at >250 samples per column and one month, respectively. Column activation and regeneration in these wire type reductors are simpler and less tedious than for reductors constructed of copperized Cd granules.     

Comparative response of corn and soybean to seed‐placed phosphorus over a range of soil test phosphorus

Abstract

The responses of corn and soybean to seed‐placed fertilizer were compared over NaHCO₃‐extractable soil phosphorus (P) levels ranging from 3 to 35 ppm in a two‐year experiment. Early season corn and soybean shoot‐P concentrations were increased with increasing soil test P and were increased with seed‐placed P regardless of soil test P, although the increases were greater for corn than soybean. Corn grain yield increased with increasing soil test P to a plateau level and increased with seed‐placed P regardless of soil test P. A side‐band (5 cm × 5 cm) application of 39 kg P ha^‐1 at a low soil test P increased yield more (P<0.15) than application of 7 kg P ha^‐1 with the seed. A side‐band application of 9 kg P ha^‐1 at a medium soil P test did not increase yield. Soybean yield was increased with increasing soil test P one year out of two, but did not respond to seed‐placed P in either year. The yield response of corn was attributed to the increased P concentration prior to the 6‐leaf stage.     

Chemical fractions of copper and zinc in organic‐rich particles from aqueous extracts of a metal‐contaminated granite soil

Abstract

Chemical fractions of copper (Cu) and zinc (Zn) in the organic‐rich particles collected from filtered aqueous extracts (<20 μm) of an acid soil were determined. A sequential extraction procedure was used to partition the particulate Cu and Zn into four operationally defined chemical fractions: adsorbed (ADS), iron (Fe) and manganese (Mn) oxides bound (FeMnOX), organic matter bound (OM) and residual (RESD). Total extractable concentrations of Cu and Zn in the fine particles were higher than their total concentrations in the original bulk soil. The concentration of particulate Cu was usually much higher than that of particulate Zn. Addition of lime stabilized sewage sludge cake and/or inorganic metal salts markedly increased the concentrations of particulate Cu and Zn in aqueous extracts, especially from limed soil. The proportional distributions of particulate Cu and Zn were quite similar. The two particulate metals were present predominantly in the ADS and FeMnOX fractions, with less (about 20%) in the OM and RESD fractions. Some of the ADS metal fraction was associated with dissolved organic substances. The concentrations of particulate Cu and Zn in the various extractable fractions were significantly affected by the application of lime, lime stabilized sewage sludge cake, or inorganic metal salts.     

The rapid determination of nitrate at low concentrations in soil extracts: Comparison of ion‐selective electrode with continuous‐flow analysis

Abstract

The efficiency of extraction of nitrate with saturated CaSCO₄ solution and with IM KCl was compared for a range of field‐moist and air‐dried soils. Saturated CaSO₄ was as effective for moist soils and slightly more effective for dried ones, and removed 95% of the nitrate after shaking for 5 min. Three methods of nitrate analysis using an ion‐selective electrode were compared with continuous‐flow analysis (CFA). All gave good correlations with CFA but only one, a “known addition” method, gave results which agreed quantitatively. This method could be applied at nitrate‐N concentrations at least as low as 0.5 mg kg^‐1.     

Application of the Berthelot reaction to the determination of ammonium‐N in soil extracts and soil digests

Abstract

The phenol‐hypochlorite‐ammonium reaction of Berthelot can be utilized in manual procedures for the analysis of NH₄‐N in a variety of soils applications, including total N measurement in soils, particle size separates and soluble organic matter fractions, and in measuring NH₄‐N in soil extracts. A simple, convenient, and versatile procedure is described.     

Application of near‐infrared spectroscopy in analysis of soil mineral nutrients

Abstract

The feasibility of using near‐infrared reflectance spectroscopy (NIRS) was investigated for the analysis of pH, electrical conductivity (EC), phosphorus (P), sulfur (S), calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), iron (Fe), and manganese (Mn) in 28 Canadian soil samples from three boreholes down to 10 m in depth. Field moist soil samples were scanned for pH and EC, and air‐dry samples were scanned for the analysis of the elements. Calibrations were developed between the near‐infrared spectral data and results obtained by conventional analyses. The NIR‐predicted values were highly correlated to the measured values obtained by the conventional methods (r²>0.9) for P, Ca, Mg, K, Fe, and Mn, and almost as highly correlated (r²>0.8) for S and Na Results for pH were somewhat less successful (r²>0.6), and appeared to be useful only for screening purposes, whereas EC was not successfully predicted by NIRS in this study. It appeared that NIRS could be a useful method for the rapid, non‐destructive, simultaneous analysis of elemental concentrations in dry soils, useful in routine analysis.     

Comparison of phosphate rock and triple superphosphate on a phosphorus‐deficient Kenyan soil

Abstract

Soil phosphorus (P) deficiency is a constraint to crop production in many regions of sub‐Saharan Africa, which could be overcome through use of either soluble P fertilizer or sufficiently reactive phosphate rock (PR). A field study was conducted with corn (Zea mays L.) for three growing seasons (18 months) on a P‐deficient, acid soil in Kenya to compare a soluble P source (triple superphosphate, TSP) and relatively reactive Minjingu PR from Tanzania. In the 18 months following application of 250 kg P ha^‐1, bicarbonate extractable inorganic soil P (P_i) was higher for application of TSP than PR, but Pi extracted with a mixed anion‐cation resin was comparable for TSP and PR. Inorganic P extracted by 0.1M NaOH, without prior extraction of resin and bicarbonate P_i, decreased during the 18 months following TSP application, but increased following PR application. After 18 months, about 7% of the added PR‐P remained as Ca‐bound P that was extracted with 1M HCl. The 1M HCl extractable P., however, underestimated residual PR‐P that gradually dissolved and supplied plant‐available P, as indicated by recovery of <40% of PR‐P added to soil in laboratory incubations even though PR solubility in HCl was >90%. Minjingu PR was an effective source of P for corn. Corn yields were comparable for TSP and PR, and the relative agronomic effectiveness of PR averaged 107% in Season 1 and 79% in Season 3. Anion resin and mixed anion‐cation resin appeared to be superior to bicarbonate and NaOH as a soil P test for use with both TSP‐ and PR‐treated soils.     

Residual Effect of Phosphorus Fertilizer in a Low‐Humic Andosol with Low Extractable Phosphorus

Abstract

Phosphorus (P) fertilization is quite important for crop production grown on Andosols. Fertilizer P‐use efficiency was 17% in a long‐term wheat experiment on a low‐humic Andosol. Residual effects of P fertilization were investigated using field soils in pot experiments. Topsoil was collected from the plots with or without annual P fertilizer at the rate of 65 kg‐P ha^?1 for 23 years (nitrogen phosphorous potassium (NPK) soil and nitrogen potassium (NK) soil, respectively). There was no significant difference in dry matter of wheat and P uptake between NPK and NK soils. However, dry matter of rice and P uptake were higher in NPK soil than in NK soil. Inorganic aluminum P (Al‐P_i) and iron P (Fe‐P_i) increased in NPK soil. Increase in Al‐P_i and Fe‐P_i during 23 years contributed little to P uptake by wheat, and repeated P fertilization is indispensable to obtain acceptable grain yield.     

Adding selenium‐enriched plant tissue to soil causes the accumulation of selenium in alfalfa

Greenhouse experiments were conducted to determine selenium (Se) uptake by alfalfa (Medicago sativa L.) grown in soils amended with Se‐laden mustard plant tissue. The experimental design was a completely randomized block with treatments consisting of 5, 10, 20, and 40 g of added dried Se‐containing mustard tissue to the soil, which resulted in soil Se concentrations of 1.0, 1.6, 3.0, and 5.7 mg Se/kg, respectively. Four clippings of alfalfa were made and the vegetative portions analyzed for dry weight and total Se. Plant dry weight yields and heights of plants were significantly reduced only at the highest Se treatment rate. Mean tissue Se concentrations increased from 1.8 mg Se/kg DM at the 5 g treatment rate to 6.0 mg Se/kg DM at the 40 g treatment rate. Based on this study, alfalfa can accumulate Se during establishment year when Se‐laden mustard plant tissue is added to the soil.     

Calcium‐ and iron‐related phosphorus in calcareous and calcareous marsh soils: Sequential chemical fractionation and 31p nuclear magnetic resonance study

Abstract

Phosphorus (P) forms in soils determine the amount of P available for crops and the potential for this element to be released to water. Sequential chemical fractionation can provide some information about major P forms in soils, and allow one to distinguish iron (Fe)‐related phosphorus from calcium (Ca)‐bound P. The ³¹P nuclear magnetic resonance (NMR) spectroscopy has been used in the identification of organic P, precipitated Ca‐phosphates, and aluminum (Al)‐related P in acid soils. Three calcareous soils and four calcareous marsh soils were used in this study. These two types of soils differ in the nature of iron oxides, which are the main P sorbent surfaces. The ratio of low crystalline to high crystalline iron oxides is higher in marsh soils than in calcareous soils as a consequence of the special genesis and conditions of the soil (reduction‐oxidation cycles). Such a ratio is related to the proportion of occluded P in low crystalline oxides relative to that of high crystalline oxides. Citrate‐bicarbonate extractable P (CB‐P) in the fractionation schemes can be ascribed to adsorbed P and high soluble calcium phosphates. CB‐P is correlated with the sum of P fractions in all the soils, thus indicating that the amount of the P that can be easily released is related to the rate of P enrichment of the soil. The ³¹P NMR spectral data reveal that hydroxyapatite is the dominant P form in the soils studied. This is consistent with the fractionation data, where acid‐extractable P is the main P fraction. The spectra also provide some information about the amount of total inorganic P and Ca‐phosphates in calcareous soils.     

Yield and phosphorus efficiency of some lowland rice varieties at different levels of soil‐available phosphorus

Abstract

A field experiment was conducted on an Aerie Haplaquept soil to study the effect of phosphorus (P) deficiency in soil on the P nutrition and yield of five modern varieties of rice, viz., Purbachi, BR1, BR3, BR14, and BR29, popular with the rice farmers of Bangladesh. Soil‐available P in the different plots of the experimental field varied widely, from 2.8 to 16.4 ppm. This plot to plot variation in soil‐available P content resulted from differences in the total amounts (0 to 480 kg ha^‐1) of P the plots had received over a period of 8 years in a long‐term P fertilizer trial conducted previously in the same field. Phosphorus deficiency in soil drastically reduced the grain yield of all the rice varieties. In severely P deficient plots, where soil‐available P was around 3 ppm, the yield was less than 1 ton ha^‐1 while in plots containing an adequate P level, i.e., >6 ppm, the yield was more than 41 ha^‐1. Rice yield increased linearly with an increase in soil P content up to 6 ppm, and the highest grain yield for any variety, obtained at 6–7 ppm of soil‐available P leveled off at this point. Soil P deficiency not only decreased rice yield severely but also decreased P content in straw and grain drastically. However, differences among rice varieties were noted in P nutrition, particularly at low soil P levels. The rice varieties differed markedly also in respect of internal P efficiency. The BR29 showed the highest internal P efficiency both at low and high soil P levels. In all the rice varieties, internal P efficiency decreased with an increase in soil P levels.