The total amount of a nutrient in the soil does not generally reflect the quantity available for uptake by plant roots. Thus, chemical methods have been developed, and continue to be developed, to estimate the quantity of a nutrient that is available to the plant. In addition to the requirement that the method provide a good estimate of nutrient availability in a defined range of soil types, soil analysis methods must be rapid, accurate, and reproducible before being accepted for routine use in soil testing laboratories.

The results of soil analyses are interpreted on the basis of previously-established relationships between crop yield and soil test. These relationships may be established by means of glasshouse pot experiments or field experiments. In either case, they are specific to both the soil type and the crop species (and to some extent, the cultivar) used in the experiments, and can be applied to other crops or soils only with a degree of caution and uncertainty.

One advantage of soil analyses is that they can be conducted, and fertilisers applied, before a crop is planted. Disadvantages of soil analyses include the difficulty of obtaining methods suited to varied soil types, problems in sampling due to soil variation across a field, and problems in estimating the likely effects of environmental conditions in the forthcoming season.

Source: O’Sullivan, J.N., Asher, C.J. and Blamey, F.P.C. (1997) Nutrient Disorders of Sweet Potato. ACIAR Monograph No. 48, Australian Centre for International Agricultural Research, Canberra, 136 p.

Previous Page:

Diagnosing nutritional disorders

Next Pages:

Visible symptoms of nutritional disorders

Plant tissue analysis

Related topics:

Soil management

Plant nutrients

Fertilisation

Causes of nutritional disorders

Correcting nutritional disorders

Sampling soil for analysis from a garden in PNG (J. O'Sullivan).