Flow Injection Analysis

Plant analysis (sometimes referred to as leaf analysis) is the determination of the total elemental content of a specified plant part. The emphasis in this chapter will be on the determination of those elements required for plant growth. Interpretation is normally based on the use of a "critical value" or "sufficiency range" (Smith, 1962) comparison between the elemental concentration found and a known norm (Goodall & Gregory, 1947; Chapman, 1966; Reuter & Robinson, 1986; Adriano, 1986; Martin-Prevel et al., 1987). An alternative method of interpretation is Diagnosis and Recommendation Integrated System (ORIS), which interprets the ratios of elements (N/P, K/Ca, and K/Mg) as indicators of elemental status (Beaufils, 1973; Sumner, 1977, 1982). Most growers primarily use a plant analysis for diagnosing suspected elemental insufficiencies, while its most significant, yet little used application, is for evaluating the soil/plant elemental status. This is partially reflected in the relatively few plant tissue samples assayed for growers, about 500 000, in the USA each year (Jones, 1985). Tissue testing, an elemental assay of extracted cell sap by means of quick chemical tests in the field, seems to be gaining an interest at levels equal to that observed several decades ago. A plant analysis is carried out in a series of steps as shown in Fig. 15-1. The results obtained are no better than the care taken in collecting, handling, preparing, and analyzing the collected tissue. An error made in one of these steps can result in an erroneous interpretation leading to recommendations that may be either unnecessary, costly, or even damaging to the crop. Therefore, it is important for those employing either a plant analysis or tissue test to follow the proper sampling, preparation, and analysis procedures. This chapter deals with the procedures required to successfully conduct a plant analysis or tissue test.

Sampling, handling and analyzing plant tissue samples.

THE importance of dissolved organic nitrogen in ecosystem nutrient fluxes and plant nutrition is only beginning to be appreciated1,2. Here we report that the polyphenol concentration of decomposing Pinus muricata litter controls the proportion of nitrogen released in dissolved organic forms relative to mineral forms (NH+4 + NO-3). We have previously shown that concentrations of polyphen-ols in P. muricata foliage vary along an extreme soil acidity/ fertility gradient3. Apparently this feedback to soil conditions controls the dominant form in which litter nitrogen is mobilized, facilitating nitrogen recovery through pine-mycorrhizal associations, minimizing nitrogen availability to competing organisms, and attenuating nitrogen losses from leaching and denitrification. Polyphenol control of nitrogen dynamics helps explain the convergent evolution of tannin-rich plant communities on highly leached soils.

Polyphenol control of nitrogen release from pine litter

Long-term effect of chemical fertilizer, straw, and manure on soil chemical and biological properties in northwest China

An expedient digestion method for serial determinations of N‐total, P, Na, K, Ca and Mg in plant material is proposed. All determinations are performed on one digest, the only limitation being that the Ca content should not exceed 1100 mmol Ca per kg dry plant material.

A novel digestion technique for multi-element plant analyses

A digestion mixture suitable for the decomposition of soil and plant materials is described. This is based on sulphuric acid and hydrogen peroxide as oxidants with the addition of lithium sulphate to elevate the digestion temperature and selenium as catalyst. The subsequent solution is suitable for the determination of nitrogen, phosphorus and most mineral ions. A series of tests have been carried out to determine optimum conditions and check elemental recoveries and the procedure is compared with alternative systems.

A wet oxidation procedure suitable for the determination of nitrogen and mineral nutrients in biological material

Samples of vegetation and faeces from heavily grazed pastures are likely to be contaminated with soil to some extent. The determination of total potassium on these samples will result in low recoveries if a wet oxidation procedure normally used for vegetation analysis is employed. However, data are presented which show that for the sites studied satisfactory recoveries of total potassium are obtained following a sulphuric acid‐hydrogen peroxide digestion, providing the ash content of the sample does not exceed 25%. For ash contents greater than 25%, alkaline fusion or hydrofluoric/perchloric acid decomposition procedures are required to obtain full recovery.

J. A. Parkinson

Papers

A wet oxidation procedure suitable for the determination of nitrogen and mineral nutrients in biological material

Determination of total potassium in vegetation and sheep faeces contaminated with soil