Procedures for Soil Analysis

This laboratory manual presents the procedures for soil analysis as they were in use at ISRIC at the time of writing (1986-2002). Indeed, because of changes within procedures or the introduction of new procedures and laboratory equipment such a manual can only be a snapshot of a moving scene. This touches on a dualism in soil analytical work: on the one hand there is the continuous pursuit of innovations and improvements and on the other the necessity of general acceptance and use of the same procedures by as many laboratories as possible. A number of the analyses described in this manual is aimed at characterisation of soils for the purpose of soil classification and correlation. Several classification criteria are based on specified, possibly archaic analytical procedures and the introduction of new and “better” techniques to replace the old may sometimes be a long-winded affair. An example is the CEC determination with the silver-thiourea method which is included in this manual because it seems to be a rapid and convenient substitute for the well-established but much abused ammonium acetate method.

Performance of an analysis according to more than one method, not only as a method-correlation exercise but also as a routine procedure, may in some cases be a rewarding informative investment, e.g. CEC at more than one pH value or particle size analysis with different pretreatments. Nevertheless, a good deal of the new developments, adaptations and improvements that become available regularly is useful and easy to adopt and it is foreseen that this manual has to be updated and extended regularly.

The procedures were compiled in cooperation with the laboratory staff of ISRIC: Messrs. J.G. ten Bokkel, J.R.M. Huting, B. van Lagen, A.J.M. van Oostrum, and R.A. Smaal. Much information was drawn from manuals in use by other laboratories working in the same field. These are mentioned under the references of the procedures concerned. The helpful discussions with Mr. L.Th. Begheijn and Dr. V.J.G. Houba of the Wageningen Agricultural University are gratefully acknowledged.