The field experiment being carried out by the IRG (described in document IRG/WP/367) is designed to obtain information on the performance of a preservative in different hardwoods in ground contact. A total of 57 timber species is being examined and 36 different field sites are involved representing a complete range of climatic conditions. IRG document WP/384 describes the treatment details of the trial. At the inception of the trial a decision was taken to limit the experiment by including only one preservative and this was chosen as a copper-chrome-arsenic type conforming to British Standard BS 4072 : 1974. The wisdom of that decision is now clear since, even with one preservative, there are more than 6000 stakes involved. At the IRG meetings in the last three years this experiment has been considered in the general discussion of soft rot in hardwoods, and the desire has been expressed to extend the scope to an evaluation of the performance of hardwoods treated with other preservatives. In this connection, creosote, copper-chrome-boron, copper-chrome-fluoride and PCP in fuel oil have been mentioned. In view of the length of time required to plan a co-operative trial up to the time of installing the stakes in the test plot it is apparent that the next stages of the work, involving detailed tests using other preservatives, will not be completed for some time. A programme was therefore planned by the authors to carry out a limited experiment on the lines of the first formal IRG field trial, but using CBC, PCP and creosote as the preservatives. By carrying out the treatments quickly it we hoped to be able to install the test stakes with a minimum of delay after the setting out the stakes in the main trial. It was decided to use three of the main experiment reference species. Betula pendula, Fagus sylvatica, Pinus sylvestris and one additional hardwood Eucalyptus maculata. It was further decided to expose the treated stakes at two sites, in the UK and Australia.

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