Method 76 Determination of nitrate in plant material by autoanalysis

See the discussion with references in Chapter 4 'Nitrate and water soluble carbohydrate'. Soil extracts low in colour may also be analysed by this procedure by taking a 10-ml scoop of fresh or thawed soil. The official Bran+Luebbe AutoAnalyzer method for nitrate and nitrite in soil, plant and fertilizer extracts is reproduced with permission in Appendix 5. Ammonium chloride buffer, pH 7.5 - dissolve 400 g ammonium chloride (NH4Cl), 40 g EDTA disodium salt, 40 g sodium dihydrogen phosphate...

Potassium extractants

Potassium occurs in soil clay minerals, feldspars and micas. The unweathered illite region of the clay mineral contains non-exchangeable K+, the weathered vermiculite region has exchangeable K+, while the intermediate region has slowly exchangeable K+. There is also available potassium in the soil solution. The extractant will leach the free potassium ions and displace the exchangeable and some slowly exchangeable K+ by replacing the K+ with Na+, H+ or NH4+, depending on the extractant. Various...

Aciddigestion of soils

There are three main reasons for digesting soils in hot acid - to determine the organic carbon content, to extract mineral elements for their total content, and to determine total nitrogen by the Kjeldahl digestion. The first is called Tinsley's wet combustion (Tinsley, 1950), and uses a highly corrosive mixture of sodium dichromate, and concentrated perchloric and sulphuric acids. For undergraduate practical classes, the safer loss on ignition method might be considered more appropriate. The...

Method 61b with final determination by autoanalysis

The acid digest from Method 6.1b consists of a solution of 0.05 g sample in 50 ml of 50 v v H2SO4. There are therefore 50,000 pg sample in 50 ml, or 1000 pg ml-1. If the fertilizer is a super triplephosphate with approximately 20 P, this would give a solution of approximately 200 pg P ml-1. The autoanalysis method is the one described in Chapter 7 for total phosphorus in plant materials, which requires an optimum sample concentration of from 20 to 100 pg P ml-1, therefore 5 ml of the super...

Near Infrared Spectroscopy

Practical instructions regarding this method of analysis are beyond the scope of this book, however, some details will be given to provide a background for those wishing to make use of commercial services. Some material was originally published in Faithfull (1996). What exactly is NIRS The near infrared region of the electromagnetic spectrum is a region having a range of wavelengths slightly longer than visible light but not as long as microwaves or the longer radiowaves. A beam of light from a...

Discussion 55 Determination of available nitrogen

The available nitrogen is equivalent to the mineralized nitrogen, which consists of the soluble nitrate and nitrite, and the exchangeable and soluble ammonium nitrogen. These compounds fluctuate over short periods and are greatly affected by microbial activity the ammonia gas may escape from the sample by volatilization. The soil sample should be transported in an icebox and transferred to a freezer unless immediately analysed. If just the available nitrate is required, it may be analysed...

Fibre lignin cellulose nitrogenfree extract and starch

Crude fibre is an attempt to measure the roughage material in a feedstuff that is indigestible as far as the animal is concerned. It is an attempt to approximate the effect on the feedstuff of the digestive processes within the digestive tract by the use of inorganic chemicals, in this case, boiling dilute sulphuric acid, then boiling dilute sodium hydroxide, and the weight loss on ignition (which corrects for mineral ash content) of the residue is the fibre content....

Method 62aii Determination of watersoluble phosphorus manual method

This method and the following (6.2b.) are based on the methods given by Craven and Schwer (1960). The concentrations of standard solutions are expressed in terms of mg P2O5, sometimes incorrectly termed phosphoric acid. We have retained this format in order to give exact increments of concentration for the sequence of standards. It is now conventional, however, for the analytical method to express phosphorus concentration in terms of elemental P, and then convert to P2O5, which is still used...

Discussion 78 Determination of oil in feeding stuffs by extraction with petroleum spirit

The official EC method may be downloaded from This is document 398L0064 (which is presented in the Official Journal No. L257, 19.09.98, pp.14-28), and is the Commission Directive 98 64 EC of 3 September 1998. The determination of crude oils and fats appears as Part B of the Annex. Two procedures are described Procedure A is the directly extractable crude oils and fats applicable to feed materials of plant origin and is a simple extraction with petroleum spirit (light petroleum, boiling range...

Method 513 Determination of CEC in composts

Barium acetate reagent, 0.5 M, pH 7.0 - dissolve 127.7 g barium acetate Ba(CH3COO)2 in water and make up to 1 l. Adjust to pH 7.0 using acetic acid and or barium hydroxide solution as appropriate. Thymol blue indicator (thymolsulphonphthalein) - triturate 1 g thymol blue (acid form) in a clean glass mortar with 21.5 ml 0.1 M sodium hydroxide and dilute to 1 l with water. Procedure. Place 0.2 g compost, milled to 0.75 mm (approximately 24 or 25 mesh) into a sintered glass filter funnel...

Method 81 Determination of ammoniumN in silage

A distillation method is given in MAFF ADAS (1986, pp. 168-169), but a selective ion electrode method will be described below. Alkali reagent (disodium EDTA, 0.1 M + sodium hydroxide, 2 M) - weigh 80 g NaOH and 37.2 g disodium EDTA into a beaker and dissolve in ammonia-free water. Transfer to a 1-l volumetric flask, and when cool make up to the mark and mix. Ammonia-free water - add about 6 ml sulphuric acid (approx. 98 m m H2SO4) to 2 l water and distil off sufficient ammonia-free water,...

Discussion 62 Determination of phosphorus in fertilizers

The analysis of phosphorus in fertilizers can be achieved in many ways, and due regard must be made both to the chemical form in which the phosphorus occurs, and its solubility, and hence relative rate of availability to the plant. Phosphorus can occur in many different molecular combinations and admixed with a variety of other substances, organic and inorganic, so that it is difficult to recommend one method in preference to any other. The type and amount of accompanying trace elements can...

Method 512a Determination of extractable sulphur manual method

The determination of extracted sulphate-S may be carried out by ICP, ion chromatography or turbidimetry. The ICP procedure measures both organic and inorganic S present in the extract, but has a low methodological error. Ion chromatography may be affected by interference from phosphates and speed of sample throughput, but a suitable method is given by Combs et al. (1998). The most widely used method is by turbidimetry, where sulphate is precipitated as a white suspension of...

Extraction Procedures Soils

There are many different types of soil, and extractant formulations have been fine-tuned to suit the soil. The particular extractant may also be chosen on the basis of familiarity over the years, and because it is easier to compare results with those previously obtained, and hence make recommendations to correct deficiencies based on experience. Usually one is not interested in the total amount of a soil nutrient, rather in the amount that is in a form available to the roots of the plant....

Discussion 512 Determination of extractable sulphur

A helpful discussion of sulphur in soils and its availability to plants is found in Combs etal. (1998) and Rowell (1994, pp. 213-215). Plants absorb sulphur mainly in the form of sulphate, which is the main form of sulphur occurring in the soil solution. The SO4-S is therefore the fraction usually measured. Over 90 of the surface soil sulphur occurs in combination with organic molecules from where it is mineralized to sulphate. The SO4-S concentration has been found to increase from...

Method 512b Determination of extractable sulphur automated method

An automated method should improve reproducibility by maintaining constant conditions for the formation of the BaSO4 precipitate. A method suitable for the segmented-flow analysis of sulphate in soil and plant extracts using Skalar Analytical equipment has been proposed by Coutinho (1997). Soils are said to be extracted with double-distilled water according to the method in MAFF ADAS (1986, pp. 215-216), however, that reference uses approximately 1.5 M HCl (10 g soil extracted with 70 ml water...

Discussion 710 Determination of total phosphorus in plant material and feeding stuffs

The official EC method may be downloaded from This is document 371L0393 (which is presented in the Official Journal No. L279, 20.12.71, p.7), and is the Second Commission Directive 71 393 EEC of 18 November 1971. The determination of total phosphorus appears as Part III of the Annex. It is a molybdovanadate colorimetric procedure with the absorbance measured at 430 nm. The AOAC alkalimetric ammonium molybdophosphate and photometric molybdovanadate methods for animal feed are described by...

In vitro digestibility

The estimation of animal digestibility of a feedstuff is usually achieved in one of three ways in vivo, in sacco or in vitro. The first uses real animals in feeding trials and gives the most realistic results to which the other methods are correlated the second method allows feed samples contained in small permeable plastic (e.g. nylon) bags to be inserted through a cannula into the rumen or another section of the digestive tract. The last method allows the digestion of feed samples to occur in...

Discussion 63 Determination of potassium in fertilizers

If the fertilizer is a straight potassium fertilizer such as potassium chloride (muriate of potash), sulphate or nitrate, it may be extracted by shaking with water. For any fertilizer, including mixed or compound fertilizers, the AOAC official method (No. 983.02B, Preparation of sample) recommends extraction with boiling 4 ammonium oxalate solution. The ammonium oxalate was introduced to precipitate calcium, which could suppress the potassium reading by up to 2.5 in an erratic fashion (Schwer...

Method 59c Determination of resin extractable phosphorus automated method

The extraction method of Hislop and Cooke (1968), has been outlined in Chapter 4, 'Phosphate extractants'. A blank determination without soil should be carried out. The autoanalysis manifold is shown in Fig. 5.4. Some adjustments to dilution and or readout sensitivity may be necessary to handle both Table 5.1. Shoulder colour code for peristaltic pump tubing. 0.03 0.05 0.10 0.16 0.23 0.32 0.42 0.60 0.80 1.00 1.20 1.40 1.60 2.00 2.50 2.90 3.40 3.90 agricultural (lower P) and glasshouse (higher...

Method 74 Determination of neutral cellulase plus gamanase digestibility NCGD of feeding stuffs

The method is based on that of MAFF (1993b) and is discussed in Chapter 4. It is intended for samples of compound feeds or feed mixtures. Filter tubes - a special sintered borosilicate glass filter tube with Suba-Seal and plastic cap is available from Soham Scientific, Unit 6, Mereside, Soham, Ely, Cambs CB7 5EE, UK, and is shown in Fig. 7.1. Enzymes - test kits of consistent quality are obtainable from Biotal Limited, 5 Chiltern Close, Cardiff, CF4 5DL, UK tel. +44 (0)2920 766716, fax +44...

Method 103 Determination of total nonstarch polysaccharides

This is based on the procedure by Englyst and Cummings (1984) who performed a GLC analysis of the alditol acetate derivatives of the constituent sugars. It incorporates slight modifications as currently carried out at IGER, Aberystwyth (Paul Thomas, IGER, Aberystwyth, 2001, personal communication). The starch is first dispersed with dimethyl sulphoxide, which disrupts intermolecular hydrogen bonds, followed by hydrolysis with a-amylase and pullulanase. The former hydrolyses the straight chain...

Method 511 Determination of extractable trace elements

For a discussion on the nature of the extractants, see Chapter 4 'Trace element extractants'. The method described below will use the complexing reagent DTPA (diethylene-triaminepentaacetic acid) to extract, by chelation, copper, iron, manganese and zinc (including zinc on calcareous soils) it also shows promise for monitoring cadmium, nickel and lead in soils receiving sludge appli cations. The amount of nutrient extracted will vary with extractant pH and concentration, shaking time and...

Phosphorus potassium and magnesium

These elements are determined at pH 3.6 according to the Egner-Riehm dou-ble-lactate extraction method (Egner et al., 1960 VDLUFA, 1991 sections A.6.2.1.2 and A.6.2.4.2). The solubility of phosphorus in the soil is influenced by its biological activity and humus content. Soil microflora excrete organic acids such as acetic (weak), lactic (medium) and citric (strong), and these are chosen as extractants. The acetic acid-sodium acetate extraction is that of Morgan (Lund et al., 1950), using 5 g...

Milling Grinding and Homogenization

Animal tissue is often blended in a high-speed blender until completely homogeneous. For trace element work, solid samples should not be ground in a mill constructed with materials containing the elements to be determined, such as iron, chromium and manganese. In this case, a mortar grinder (mortar and pestle mill) or ball mill would be suitable. The former may be constructed of agate, with the pestle and mortar being independently motor driven (Pascall Model 00, Agate), or may consist of a...

Subsampling

A bulk sample should be thoroughly mixed until homogeneous, then a sub-sample taken. There are two main ways to achieve this when dealing with solid samples. First, there is the manual cone and quartering method. A spoon-shaped spatula is used to take portions randomly from the bulk sample, which are then transferred to a clean surface to form a new conical pile. Each successive portion is poured on to the apex of the cone until the entire heap has been transferred. The cone is then flattened,...

Acknowledgements

First, I would like to express my gratitude to the teachers, lecturers and industrial scientists who have instilled a high regard for practical analytical chemistry, with the need for care, accuracy, and the development of a skilful and safe technique. There are a number of individuals who have been most helpful in my search for information. It is difficult to remember everyone I have consulted over a period of 18 months, and my sincere apologies for any omissions. They include the following,...

Method 51 Determination of extractable boron

The predominant form of boron in soil solution is H3BO3, but above pH 9.2, H2BO3 may predominate. Hot-water extraction is the most widely accepted procedure for determining the amount of boron that is available to plants, and correlated best with the incidence of black spot in garden beets Missouri Agricultural Experiment Station, 1998 . The final determination is best performed using an ICP spectrometer, but this may not always be available, so a colori-metric method will be described. Methods...

The Analysis of Fertilizers

There are several publications detailing standard or officially recognized methods of fertilizer analysis. These include Official Methods of Analysis of AOAC International Horwitz, 2000 Official and Standardised Methods of Analysis, published by the Royal Society of Chemistry Watson, 1994 and Fertilisers - Methods of Analysis used in OEEC Countries OEEC, 1952 . There are also the EEC methods, which have been implemented in the UK by the Fertilisers Sampling and Analysis Regulations 1996...

Discussion 84 Determination of volatile fatty acids VFAs in silage

Methyglucuronoxylobiose

We still await a routine method for the rapid analysis of large batches of silage samples for VFAs. Although initially expensive, the use of NIRS on fresh silages would be ideal, but sufficiently robust equations for components other than lactic, acetic, propionic and butyric acids are not yet widely available, although it is reported that commercial services are offering VFA analysis by NIR. The abstract of the poster by Deaville and Givens 1996 is apparently the only published data in this...

Method 57b Determination of easily oxidizable organic C by Tinsleys wet combustion

If the soil organic matter contains an element in a fairly constant percentage, then the determination of that element should enable deduction of the organic matter. This has been attempted by determining nitrogen, but this was found to vary too widely in organic soil materials. More commonly, carbon has been determined. It is assumed that soil organic matter contains on average 58 carbon, so that multiplication of the value for carbon by 1.72 100 58 will give the percentage organic matter. The...