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 (Statutory Instrument (SI) 1996 No. 1342). The title page of the SI may be downloaded from the following website  

The European Commission Directive 77/535/EEC of 22 June 1977 on the approximation of the laws of the Member States relating to methods of sampling and analysis for fertilizers is obtainable at  

The Government of India Fertilizer (Control) Order 1985, Schedule-1, Specifications of Fertilizers, is downloadable from  

Methods of fertilizer analysis are also occasionally reviewed in the Proceedings of the International Fertiliser Society, and the contents of all the Proceedings are viewable at  

---

Cindy Wiebeck of the Nebraska State Agriculture Laboratory aspirates calcium standards into the atomic absorption flame in order to calibrate the instrument for the analysis of fertilizer for calcium. In the background, note the hollow cathode lamps held in a rotating turret in the instrument. 

Neutral Ammoniiun Citrate.—A solution of this salt is used in the analysis of fertilizers to represent the solvent action of plant juices and soil water. 

Ferric ammonium citrate (C6H607Fe.C6H60r(NH4)2H), is used in making blue-print paper (242). A strong solution of neutral ammonium citrate is used in the analysis of fertilizers in the separation of the different forms of phosphates which the fertilizers contain. 

AOAC International was formed in the United States of America in 1880 at a meeting attended by government and university scientists and officials concerned with the analysis of fertilizers. Initially, the association was formed as a section of the chemistry subdivision of the American Academy of Sciences, adopting a committee... 

The legal basis for the sale of fertilizers throughout the world is laboratory evaluation of content as available nitrogen, phosphorus, and potassium. By convention, numerical expression of the available nutrient content of a fertilizer is by three successive numbers that represent the percent available of N, P20, and K O, respectively. Thus, for example, a 20—10—5 fertilizer contains available nitrogen in the amount of 20% by weight of N, available phosphoms in amount equivalent to 10% of P2O5, and available potassium in amount equivalent to 5% K O. The numerical expression of these three numbers is commonly referred to as the analysis or grade of the fertilizer. Accepted procedures for laboratory analysis are fixed by laws that vary somewhat from country to country. 

The analysis of cocoa shell (7) is given in Table 4. In the United States, shells are often used as mulch or fertilizer for ornamental and edible plants, as animal feed, and as fuel for boilers. 

For confirmatory assay, liquid chromatography-tandem mass spectrometry (LC-MS/MS) is becoming more frequently used in the analysis of OTC owing to its high sensitivity and ability. Electrospray ionization (ESI) [55-57] and atmospheric pressure chemical ionization (APCI) [41] methods combined with tandem mass spectrometry are favored because of their higher sensitivity and better reproducibility. Hamscher et al. [58] developed a method for the determination of persistent TC residues in soil fertilized with manure by HPLC tandem mass spectrometry, MS-MS, and confirmation by MS-MS-MS. Zhu et al. [59] developed an LC-tandem mass spectrometry for the analysis of common tetracyclines in water. The detection limit for oxytetracycline was 0.21 pg/L. Lykkeberg et al. [60] used LC-MS/MS for determination of oxytetracycline and its impurities EOTC, TC, ETC, ADOTC, oc-AOTC, and /i-AOTC. 

Flame emission spectrometry is used extensively for the determination of trace metals in solution and in particular the alkali and alkaline earth metals. The most notable applications are the determinations of Na, K, Ca and Mg in body fluids and other biological samples for clinical diagnosis. Simple filter instruments generally provide adequate resolution for this type of analysis. The same elements, together with B, Fe, Cu and Mn, are important constituents of soils and fertilizers and the technique is therefore also useful for the analysis of agricultural materials. Although many other trace metals can be determined in a variety of matrices, there has been a preference for the use of atomic absorption spectrometry because variations in flame temperature are much less critical and spectral interference is negligible. Detection limits for flame emission techniques are comparable to those for atomic absorption, i.e. from < 0.01 to 10 ppm (Table 8.6). Flame emission spectrometry complements atomic absorption spectrometry because it operates most effectively for elements which are easily ionized, whilst atomic absorption methods demand a minimum of ionization (Table 8.7). 

Consider the analysis of soil from a farmer s field. The farmer wants to know whether he needs to apply a nitrogen-containing fertilizer to his field. It is conceivable that different parts of the field could provide different types of samples in terms of nitrogen content. Suppose there is a cattle feed lot nearby, perhaps uphill from part of the field and downhill from another part of the field such that runoff from the feed lot affects part of the field but not the other part. If the farmer wishes to have an analysis report for the field as a whole, then the sample taken should include combined portions from all parts of the field that may be different (a composite sample) so that it will truly represent the field as a whole. Alternatively, two selective samples could be taken, one from above the feed lot and one from below the feed lot, so that two analyses are performed and reported to the farmer. These would be referred to as selective samples. At any rate, one wants the results of the chemical analysis to be correct for the entire area for which the analysis is intended. 

Wil Kastning of the Nebraska State Agriculture Laboratory filters barium sulfate precipitates using filtering crucibles and a vacuum system while performing a gravimetric analysis of fertilizers for sulfate content. 

As for properties of calcium phophate particles grown in the reactor, chemical and physical analysis were done to verify availability of this process. Table 2 shows results of chemical analysis, which made clear that our products contained mainly calcium phosphate and some calcium carbonate and could be used as the source of fertilizer. 

Potassium sulfate is used in fertilizers as a source of potassium and sulfur, both of which are essential elements for plant growth. Either in simple form or as a double salt with magnesium sulfate, potassium sulfate is one of the most widely consumed potassium salts in agricultural apphcations. It is preferred over potassium chloride for certain types of crops such as, tobacco, citrus, and other chloride—sensitive crops. Some other applications include making gypsum cements to make potassium alum in the analysis of Kjeldahl nitrogen and in medicine. 

Burch TK, Macisco JJ, Parker MP (1967) Some methodologic problems in the analysis of menstrual data. Int J Fertil, 12 67-76. 

In a definitive series of experimental investigations H. N. Wilson showed that the quinolinium salt, (C isNJ fPCV I2M0O3]3- was anhydrous, contained exactly 12 moles of molybdenum trioxide per mole of phosphate, that the precipitate had a negligible solubility and could be dried to constant weight in two hours at 105 °C. This precipitate also lent itself to a precise alkalimetric titration. In the presence of citric acid interference by silica was inhibited so that the method was admirably suitable for the analysis of basic slags or fertilizers.34... 

Thus, there is no reason to believe that one fertilizer promotes growth more than another. Generally speaking, analysis-of-variance problems are not solved in the form used in this example. A standard form called the analysis-of-variance table has been developed, and it is particularly useful for more complex problems ... 

Soils can have characteristics due to human activity (anthropogenic soils). The forensic examination of soil is therefore not only concerned with the analysis of naturally occurring rocks, minerals, plant, and animal matter it also includes the detection of such manufactured materials as ions from synthetic fertilizers and from different environments (e.g., nitrate, phosphate, sulfate) and environmental artifacts (e.g., lead or objects such as glass, paint chips, asphalt, brick fragments, and cinders). Each of these materials can represent distinct soil characteristics. When unique particles are found in soil evidence, more precise and rapid discrimination can be achieved even if the amount of evidence recovered is microscopic (Sugita and Marumo 2004). For this reason, microscopy is often considered the most useful technique for the detection of such characteristic particles. 

The element is extractable from strong hydrochloric acid solutions into 4-methylpentan-2-one. This approach may be applied to the analysis of plant material, if the ash is extracted with the strong hydrochloric acid required.35 Kim et al.36 masked iron(m) by reduction to iron(n) with tin(n) chloride before extracting molybdenum as its thiocyanate complex with Aliquat 336 into chloroform. The latter was evaporated, and the residue extracted with 4-methylpentan-2-one prior to determination of molybdenum by AAS. The procedure was applied to soils, sediments, and natural waters. In fertilizer analysis, the thiocyanate complex of molybdenum has been extracted, after reduction of iron with tin(n) chloride, into 3-methylbutan-l-ol, and the latter extract analysed directly.37 In another thiocyanate-based procedure, total molybdenum from soils and geological materials was extracted into 4-methyl-pentan-2-one.38... 

---