A simple in vitro test tube method for estimating the bioavailability of phosphorus in feed ingredients for swine

A simplified in vitro test tube (TT) method was developed to estimate the percentage of available P in feed ingredients for swine. The entire digestion procedure with the TT method consists of three consecutive enzymatic digestions carried out in a 50-mL conical test tube: (1) Pre-digestion with endo-xylanase and beta-glucanase for 1 h, (2) peptic digestion for 2 h, and (3) pancreatic digestion for 2 or 4 h. The TT method is simpler and much easier to perform compared to the dialysis tubing (DT) method, because dialysis tubing is not used. Reducing sample size from 1.0 to 0.25 g for the TT method improved results. In conclusion, the accuracy and validity of the TT method is equal to that of our more complicated DT method (r = 0.97, P < 0.001), designed to mimic the digestive system of swine, for estimating the availability of P in plant-origin feed ingredients.     

体外透析法评定饲料磷的透析率及其可透析磷预测模型研究

采用体外透析法测定了19种植物性饲料和2种混合饲粮磷的透析率,考察了饲料总磷、植酸磷和植酸酶与透析率之间的关系,建立了体外法预测饲料可消化磷的数学模型。结果表明:外源植酸酶的添加可以显著提高磷的透析率,且这种作用对内源植酸酶含量低的饲料效果更加明显;从绝对值看,体外法测得的透析率比真消化率低,但体外法可以较准确地比较不同饲料有效磷的高低;用于预测饲料可透析磷的方程为:Y=-0.725+0.566×总磷(g/kg)-0.35×植酸磷(g/kg)+0.0044×植酸酶(g/kg)(R2=0.918,RSD=0.207,P<0.001);可以通过体外法与体内法建立的回归模型来预测饲料真可消化磷的含量,预测方程为:真可消化磷(g/kg)=0.542+1.017×可透析磷(g/kg)(R2=0.899,RSD=0.261,P<0.0001)。     

A comparison of methods for estimating fractional vegetation cover in arid regions

We compared a set of methods for estimating the fractional vegetation cover (f_c) of sparse desert vegetation over an arid region of southern Xinjiang, China. Six kinds of remote sensing inversion models (an NDVI regression, a spectral mixture analysis (SMA), a pixel dichotomy model, a three-band maximal gradient difference (TGDVI) model and two modified TGDVI models) were used to derive f_c from remote sensing data, and the results were compared with f_c values measured in the field to select an appropriate model to derive the fractional cover of sparse desert vegetation in arid regions. The NDVI regression based on field f_c and the NDVI for the sampled pixels in September 2006 showed the highest precision, while the results of 2007 showed that the NDVI regression method is inappropriate for depicting vegetation characteristics in other growing season because the empirical model highly depend on the specified in situ measurement. The SMA approaches yielded higher precision than the other models, indicating that it is applicable for analysing the coverage of sparse desert vegetation. The pixel dichotomy model can yield a high precision based on finely detailed vegetation maps. However, it requires the measurement of many parameters. The TGDVI model is simple and easy to implement, and the values that it predicted for the coverage of high-density vegetation and barren areas were close to those measured in the field, but the f_c values of sparsely vegetated areas were underestimated. The predictions of the modified TGDVI models were close to the values measured in the field, indicating that these modified models can reliably and effectively extract information on the fractional cover of sparse vegetation in an arid region. We analyzed the models’ sensitivity with respect to rainfall because the short-wavelength infrared bands used in the two TGDVI models proposed in this study are sensitive to moisture. The results showed that the modified TGDVI models’ accuracy was not affected by increasing soil moisture content caused by rain. However, the NDVI regression, SMA and TGDVI were sensitive to the change of soil moisture content. Moreover, the two modified TGDVI models yielded negative values for water sources, such as reservoirs and rivers, implying that they are effective for characterising water bodies. However, the modified TGDVI models cannot predict f_c in snow- and glacier-covered regions, producing abnormally high rather than zero values. Additionally, the predictions before and after snowfall on the top of a mountain show a linear increasing relationship, suggesting that the short-wavelength infrared band may be useful to predict snow depth.     

A comparison of wet oxidation methods for determination of total phosphorus in soils

For 15 soils with widely different extractability of phosphorus (P) two newly introduced digestion techniques for determining total P (P_t) were compared with the standard perchloric acid digestion procedure. The two digestion techniques were: (1) concentrated H₂SO₄ plus 30 % H₂O₂ at 360 °C, (2) concentrated HCl plus concentrated HNO₃ in the ratio 3:1 (aqua regia) at 140 °C. Almost equal amounts of P_t were extracted by the two methods (mean = 188.7 mg kg^—1 for H₂SO₄/H₂O₂ and 188.4 mg kg^—1 for aqua regia) which were slightly higher than the standard method (mean = 183.8 mg kg^—1). However, there is no statistical difference among the three digestion methods, suggesting that the tested methods should be useful for estimating P_t in soils with high content of organic C, eliminating the danger of explosion when hot concentrated HClO₄ is used.     

A comparison of two methods of estimating the soil pore network available to protozoa

Two methods of estimating pore size distributions in different soil horizons are discussed and compared. These methods involve the use of either an image analyser or a camera lucida. The former method is rapid, but any enlargement of the original image of the soil pores yields inaccurate porosity measurements with the image analyser. The camera lucida method involves prolonged microscopical observations, but it can yield satisfactory pore size distributions of different soil horizons and when used with a microcomputer can be used to view a selected group of pores in three dimensions. The potential use of these methods in ecological studies of soil protozoa is discussed.     

A comparison of regression methods for estimating soil-atmosphere diffusion gas fluxes by a closed-chamber technique

Continuous changes in methane (CH₄) and carbon dioxide (CO₂) concentrations inside a closed chamber were measured on the forest floor at three sites: a deciduous forest and a coniferous forest in Hokkaido, Japan, and a birch forest in West Siberia, Russian Federation. Flux estimations by three types of regression methods, exponential, nonlinear, and linear, were examined using field-collected concentration data. The pattern of change with time of the gas concentration in the headspace differed, mainly according to site but also, to a lesser extent, according to the gas. This was a function of both the chamber height and surface soil property relating to soil gas diffusion and the gas concentration profile. Flux estimations did not differ statistically between the exponential and nonlinear methods for either gas at any site, because both of those regression methods were based on diffusion theory. However, the flux values estimated by linear regression were significantly different from those estimated by the other two methods for both CH₄ and CO₂ at the deciduous forest site and for CO₂ at the coniferous forest site. Shortening the chamber deployment period improved the linearity of the curve, but did not completely eliminate the error. Our results suggest that linear regression is not a good model of the change in headspace concentration with time.     

A comparison of methods to determine total,organic, and available phosphorus in forest soils

Abstract

Several methods for the determination of soil phosphorus (P) in acidic forest soils were examined. The Parkinson and Allen digestion method removed more total P than did the ignition method, especially with mineral soils. There were problems with both the Saunders and Williams ignition method and the Bowman and Moir extraction protocol for organic P determination. The problems were more pronounced when used on organic soil samples The Bray P1 was better than the Mehlich 3 method for measuring available P in mineral soils.     

Evaluation of soil test methods for estimation of available phosphorus in some Portuguese soils: A greenhouse study

Abstract

The Egnér‐Riehm method for estimating plant‐available soil phosphorus (P) has been used as the standard soil testing method in Portugal for making fertilizer recommendations. However, this method does not accurately reflect the available P status for wheat in some representative soils from the South Region of the country. Therefore, a pot experiment was established with four Luvisols (LVx, LVv, and two different LVh soils) from the South Region of Portugal in order to evaluate the Egnér‐Riehm, Bray I, Bray II, Olsen, and Anion Exchange Resin (AER) methods for their ability to estimate available P in those soils. Wheat (Triticum aestivum L., cv. Panda) was used as test the crop. The experiment was arranged into a randomized complete block design with three replications and five rates (0, 50, 100,150, and 200 mg kg^‐1) of P added to each soil. Critical soil P levels for LVx were established in case for Bray I (27.9 mg kg^‐1), Bray II (33.5 mg kg^‐1), Egnér‐Riehm (25.4 mg kg^‐1), and AER (14.7 mg kg^‐1) soil test procedures. Regarding the other soils, the critical soil P levels could not be estimated. The obtained results confirm that the development of an universal soil test P exti action is of great importance, and that further research should be conducted in order to evaluate routine soil fertility tests in different pedoclimatic environments.     

Comparison of extractable phosphorus from two sulfuric acid methods with the Mehlich phosphorus test number one

Abstract

All mineral phosphates in soil dissolve more completely when HCl is mixed with H₂SO₄ than with the HCl alone. It was hypothesized that a new extracting solution of H₂SO₄ alone with the same ionic strength or the same acidity as the Mehlich P1 extractant would extract similar amounts of soil phosphorus (P) as the Mehlich P1 soil test. Thirty six acid soils from Alabama, Georgia, North Carolina, South Carolina, and Colorado were used in this study. These acid soils reflect wide ranges in parent materials, texture, pH, organic matter, and available soil P. They were analyzed for available soil P with the Mehlich P1 soil test and with the two H₂SO₄ methods: Method A has an extracting solution of same ionic strength (0.0875M) as the Mehlich P1 extractant, and Method B was an extracting solution of the same acidity (0.0375M) as the Mehlich P1 extractant. Correlations between the results of Mehlich P1 with Method A and Method B were 0.994 and 0.997, respectively. The measured test precision was <3.5% for all three methods. The new H₂SO₄ methods are simple and faster to conduct under routine operations than the original Mehlich P1 extractant, and because of the high correlations, the H₂SO₄ methods should predict crop response to P as well as the original Mehlich P1 extractant for acid soils.     

植物试管苗离体生根研究进展

综述了植物试管苗生根机理方面的基因表达和遗传转化,内源激素和酶类活性与生根的关系;培养基组成物矿物盐类、附加有机成分(维生素和氨基酸)、生长调节物质、蔗糖、琼脂、活性碳、酚类物质,及pH值,培养条件、通气、湿度、温度和光照对试管苗生根的影响;外植体基因型与插条生理和发育状态与生根的关系,为植物组织培养试管苗生根研究提供一定的参考.     

Evaluation of Mehlich 3 extractant for estimating phosphorus deficiency and phosphorus sorption of Zimbabwean soils

Abstract

The Mehlich 3 extractant was compared with the resin method for its ability to predict the phosphorus (P) status of Zimbabwean soils. Correlation of P extraction between the two methods and with plant growth was found to vary with soil texture. Because the Mehlich 3 extractant was less influenced by texture, it was better able to predict the P status over a wide range of soil types. The Mehlich 3 extractant correctly predicted P deficiency for all Zimbabwean soils, except for those that contained visible calcium carbonate. Mehlich 3‐extractable aluminum (Al) was very highly correlated with the maximum P‐sorption capacity of a wide range of soils, excluding those with calcium carbonate. Adoption of the Mehlich 3 extractant for multiple elemental analysis of soils in Zimbabwe is recommended, particularly if routine Al measurement is included as an indicator of soil P requirements.     

A comparison of operational remote sensing-based models for estimating crop evapotranspiration

The integration of remotely sensed data into models of evapotranspiration (ET) facilitates the estimation of water consumption across agricultural regions. To estimate regional ET, two basic types of remote sensing approaches have been successfully applied. The first approach computes a surface energy balance using the radiometric surface temperature for estimating the sensible heat flux (H), and obtaining ET as a residual of the energy balance. This paper compares the performance of three different surface energy balance algorithms: an empirical one-source energy balance model; a one-source model calibrated using inverse modeling of ET extremes (namely ET = 0 and ET at potential) which are assumed to exist within the satellite scene; and a two-source (soil + vegetation) energy balance model. The second approach uses vegetation indices derived from canopy reflectance data to estimate basal crop coefficients that can be used to convert reference ET to actual crop ET. This approach requires local meteorological and soil data to maintain a water balance in the root zone of the crop. Output from these models was compared to sensible and latent heat fluxes measured during the soil moisture–atmosphere coupling experiment (SMACEX) conducted over rain-fed corn and soybean crops in central Iowa. The root mean square differences (RMSD) of the estimation of instantaneous latent and heat fluxes were less than 50 W m⁻² for the three energy balance models. The two-source energy balance model gave the lowest RMSD (30 W m⁻²) and highest r² values in comparison with measured fluxes. In addition, three schemes were applied for upscaling instantaneous flux estimates from the energy balance models (at the time of satellite overpass) to daily integrated ET, including conservation of evaporative fraction and fraction of reference ET. For all energy balance models, an adjusted evaporative fraction approach produced the lowest RMSDs in daily ET of 0.4–0.6 mm d⁻¹. The reflectance-based crop coefficient model yielded RMSD values of 0.4 mm d⁻¹, but tended to significantly overestimate ET from corn during a prolonged drydown period. Crop stress can be directly detected using radiometric surface temperature, but ET modeling approaches-based solely on vegetation indices will not be sensitive to stress until there is actual reduction in biomass or changes in canopy geometry.     

A comparison of 5 soil phosphorus extraction methods applied to different soils of South of Iran

Phosphorus (P) fertilization is commonly based on soil testing, for which a variety of different soil P extraction methods are in use. In this research, the correlation and calibration of five extraction techniques for available P were studied: Soltanpour and Schwab, Olsen, EDTA-Na₂, Paauw and Morgan in 168 different soil samples from 63000 ha of Sirjan pistachio orchards of Kerman province, Iran. The Morgan reagent extracted the most P and then EDTA-Na₂> Olsen> Soltanpour and Schwab> Paauw extracted more phosphorus, respectively. Positive and significant correlation (P < 0.05) existed among all extractants. The correlation coefficients between different extractants and plant P concentration indicated that, EDTA-Na₂ (P < 0.01), Olsen and Paauw methods (P < 0.05) had positive and significant correlation with leaf P concentration and thus with due attention to acceptable relationship with plant indices, the Olsen and EDTA-Na₂ methods could be used to advise on available P.     

评估土壤微量元素生物有效性测定方法

Trace element-contaminated soils (TECSs) are one of the consequences of the past industrial development worldwide.Excessive exposure to trace elements (TEs) represents a permanent threat to ecosystems and humans worldwide owing to the capacity of metal(loid)s to cross the cell membranes of living organisms and of human epithelia,and their interference with cell metabolism.Quantification of TE bioavailability in soils is complicated due to the polyphasic and reactive nature of soil constituents.To unravel critical factors controlling soil TE bioavailability and to quantify the ecological toxicity of TECSs,TEs are pivotal for evaluating excessive exposure or deficiencies and controlling the ecological risks.While current knowledge on TE bioavailability and related cumulative consequences is growing,the lack of an integrated use of this concept still hinders its utilization for a more holistic view of ecosystem vulnerability and risks for human health.Bioavailability is not generally included in models for decision making in the appraisal of TECS remediation options.In this review we describe the methods for determining the TE bioavailability and technological developments,gaps in current knowledge,and research needed to better understand how TE bioavailability can be controlled by sustainable TECS management altering key chemical properties,which would allow policy decisions for environmental protection and risk management.     

A critical assessment of methods for determining organic phosphorus in savanna soils

 Two newly introduced extraction techniques for determining total organic P (P₀) were compared with the standard high-temperature ignition method in selected savanna soils of Nigeria. The two extraction techniques were: (1) concentrated H₂SO₄ and dilute base sequential extraction (18 N H₂SO₄ and 0.5 N NaOH) and (2) basic EDTA method (0.25 M NaOH plus 0.05 M Na₂EDTA). The concentrated H₂SO₄ and dilute base method extracted significantly higher total P₀ than the high-temperature ignition method and the basic EDTA extraction. The high-temperature ignition and the basic EDTA extraction gave similar total P₀ values (mean=91 mg kg^–1 for ignition and 90 mg kg^–1 for basic EDTA). The precision of the methods, determined by coefficients of variation (CV, %) associated with each P₀ determination method in the soils, was better for the concentrated H₂SO₄ and dilute base extraction method (CV=13%) than the ignition method (CV=18%) and the basic EDTA method (CV=15%). The high C : P₀ ratios determined for the high-temperature ignition and basic EDTA extraction indicated that the two methods underestimated total P₀ in the soils. The concentrated H₂SO₄ and dilute base sequential extraction appears to be suitable for the rapid determination of P₀ in savanna soils because the method can be simplified to a single-step analysis. Received: 14 November 1997     

Rapid liquid chromatographic determination of dimetridazole and ipronidazole in swine feed

A simple and rapid method is described for the determination of dimetridazole (DMZ) and ipronidazole (IPR) in swine feeds at various levels (0.11-110 ppm). The drugs are released from feed by prewetting with a buffer, followed by extraction with either methanol or methylene chloride, depending on the drug level; if necessary, an acid-base cleanup is used before the liquid chromatographic analysis. The analytes are separated on a C18 column and monitored at 320 nm for detection and quantitation. Recoveries of DMZ from several feed formulations averaged 108% at the 92.8 ppm level with a standard deviation (SD) of 4.00% and a coefficient of variation (CV) of 3.70%, 101% at the 11.2 ppm level with an SD of 11.9% and a CV of 11.8%, and 100% at the 0.112 ppm level with an SD of 9.27% and a CV of 9.25%. Recoveries of IPR averaged 77.1% at the 12.9 ppm level with an SD of 1.75% and a CV of 2.27%; IPR recoveries averaged 35.2% at the 0.129 ppm level with an SD of 3.39% and a CV of 9.63%.     

Soil test calibration studies for formulation of phosphorus fertilizer recommendations for maize in Morogoro district,Tanzania. I. evaluation of soil test methods

Abstract

Optimum crop production depends, among other things, on the maintenance of adequate plant nutrients in the root zone. The objective of this study was to find a reliable index for assessing needs for supplemental phosphorus (P) in soils of Morogoro District, Tanzania. Six indices of P availability, namely: Bray and Kurtz No. 1 (BK1), Bray and KurtzNo.2 (BK2), Mehlich 1, Mehlich 3, Olsen and ammonium bicarbonate‐DTPA (AB‐DTPA), were evaluated. Evaluation of the P indices involved relating extractable P contents by different methods with crop response data expressed as relative yields. The response data was obtained from pot trials with soil samples from ten repesentative soils designated as benchmark soils of the district. Treatments were absolute control, 0, 10, 20, and 30 mg P kg^‐1 of soil. Correlation of maize relative yields with soil test values by the six indices of P availability resulted in correlation coefficients ranging from 0.65 to 0.90. The Olsen method gave the highest r value suggesting that it was superior to the others. However, using the Cate and Nelson approach, the Olsen and ammonium bicarbonate‐DTPA methods were found to be at par and superior to the others. They each accounted for 76% of the variations observed in maize relative yields, respectively. The critical P levels for the indices were 10.50 mg P kg^‐1 for Olsen and 2.80 mg P kg^‐1 for the AB‐DTPA method. Phosphorus fertility categories were delineated in relation to Olsen extractable P as: low (<6.50 mg P kg^‐1), medium (6.50 to 23.0 mg P kg^‐1), and high (>23.0 mg P kg^‐1). Based on this classification it was determined that 16%, 25 %, and 59% of the surveyed area had low, medium, and high P levels, respectively. About 40% of the surveyed area may, therefore, require fertilization with P for optimum yields.     

综合化学法和生物标记物法评价土壤中豆磺隆的生物有效性

Bioavailability is a critical factor for assessing the environmental risk of organic pollutants in soil. In this study, extractions with 3 different solvents, including 2 aqueous solutions, calcium chloride (CaCl₂) and a phosphate buffer solution (PBS), and a mixture of aqueous solution and organic solvent, a PBS-methanol (8:2, volume/volume) mixture (PBS-M), were performed to assess the bioavailability of chlorimuron-ethyl in soil in comparison to a battery of toxicity tests in wheat seedlings. The results indicated that the peroxidase (POD) activity in wheat leaves after 7 d of exposure was one of the sensitive biomarkers of chlorimuron-ethyl in soil. The extractability of chlorimuron-ethyl by all the 3 solvents decreased with exposure time, and the rate of decrease of the PBS-M extraction between 1 and 7 d of exposure was substantially higher than those of the aqueous solution extractions. Chlorimuron-ethyl gradually changed from a water-soluble form into a soil organic matter (SOM)-bound form in the soil. The PBS extraction correlated best with the POD activity in the leaves after 7 d of exposure.