Quantification of creosote migration down wooden poles and the prevention of its depletion during flood irrigation
M Behr, A A W Baecker
Polyethylene field liners heat-shrunk onto soil-contact surfaces prevented decay of creosote-treated Eucalyptus grandis vineyard poles under flood-irrigation. The present work quantified losses of creosote from these poles after six and 24 months' service. After six months' service the mean creosote retention of unlined poles above the ground line was 12.62% (m/m dry wood), with sample retentions decreasing progressively to 4-6% at the ground line and 2-3% throughout their sub-soil profiles. These values remained similar after 24 months' service. The mean creosote retention above the ground line of lined poles after six months' service was 13.06%, however sample retentions did not decrease towards the ground line, and these remained between 13-17% throughout the sub-soil profile. After 24 months' service the mean creosote retention above the ground line of the lined poles had fallen somewhat, but sample retentions remained over 12% at, and below, the ground line. The results showed that, while slight creosote evaporation from wood above ground may have ocurred, the major phenomena affecting creosote retentions in unlined poles in soil were gravitational migration and leaching to soil, and it seemed that these factors were coupled. Primarily, the results confirmed that creosote was lost from poles by leaching to soil, and that such loss was prevented by the application of the field liners.